| R. Quattlebaum
| Nest Labs
| December 2, 2016

Spinel Host-Controller Protocol
draft-spinel-protocol-3df876d

# Abstract

This document describes a general management protocol for enabling a host device to communicate with and manage a Network Control Processor (NCP).

While initially designed to support Thread-based NCPs, the NCP protocol has been designed with a layered approach that allows it to be easily adapted to other network technologies in the future.

# Status of This Document

This document is a work in progress and subject to change.

# Copyright Notice

Copyright (c) 2016, Nest Labs, Inc. All rights reserved.

[CREF1]RQ: We may want to consider a license more appropriate for documentation.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# Table of Contents

# 1. Introduction

This Network Control Processor (NCP) protocol was designed to enable a host device to communicate with and manage a NCP while also achieving the following goals:

- Adopt a layered approach to the protocol design, allowing future support for other network protocols.
- Minimize the number of required commands/methods by providing a rich, property-based API.
- Support NCPs capable of being connected to more than one network at a time.
- Gracefully handle the addition of new features and capabilities without necessarily breaking backward compatibility.
- Be as minimal and light-weight as possible without unnecessarily sacrificing flexibility.

On top of this core framework, we define the properties and commands to enable various features and network protocols.

# 1.1. About this Draft

This document is currently in a draft status and is changing often. This section discusses some ideas for changes to the protocol that haven't yet been fully specified, as well as some of the impetus for the current design.

# 1.1.1. Renumbering

Efforts are currently maintained to try to prevent overtly backward-incompatible changes to the existing protocol, but if you are implementing Spinel in your own products you should expect there to be at least one large renumbering event and major version number change before the standard is considered "baked". All changes will be clearly marked and documented to make such a transition as easy as possible.

To allow conclusive detection of protocol (in)compatibility between the host and the NCP, the following commands and properties are already considered to be "baked" and will not change:

- Command IDs zero through eight. (Reset, No-op, and Property-Value Commands)
- Property IDs zero through two. (Last status, Protocol Version, and NCP Version)

Renumbering would be undertaken in order to better organize the allocation of property IDs and capability IDs. One of the initial goals of this protocol was for it to be possible for a host or NCP to only implement properties with values less than 127 and for the NCP to still be usable---relegating all larger property values for extra features or other capabilities that aren't strictly necessary. This would allow simple implementations to avoid the need to implement support for PUIs (Section 3.2).

As time has gone by and the protocol has become more fleshed out, it has become clear that some of the initial allocations were inadequate and should be revisited if we want to try to achieve the original goal.

# 1.1.2. Spinel as Application API

The current primary host driver implementation is wpantund. wpantund manages the NCP using the Spinel protocol and provides a management API for the application using D-Bus IPC.

However, some thought has been given to the idea of having a host driver daemon which uses Spinel directly as the management API. You would have user-space daemon similar to wpantund which would communicate directly with the NCP. Using Unix Domain Sockets, applications could connect to the daemon by opening a special socket file. The protocol for that socket might be (for example) HDLC-Lite-encoded (Appendix A.1.2) spinel frames, as if the application were talking directly to the NCP.

Applications aren't necessarily interested in everything that an NCP would normally send out unsolicited, so a mechanism for specifying which properties should be listened to would need to be defined. This mechanism would not be implemented by the NCP but would instead be implemented by the daemon to control which notification packets need to be directed where.

In the event of transaction ID collisions, the daemon would transparently renumber spinel frames so as to not cause TID collisions.

Since there can be more than one application that is using the API at a time, the `PROP_LOCK` property (Section 5.2.10) would be used to ensure exclusive access to the NCP by an application. Only one process would be allowed to enable the lock at a time.

Such a IPC mechanism would be desirable because it is, from a spinel perspective, future proof. New features can be added and new properties assigned and the IPC protocol would not need to be extended to support them. It is also simple and has no external dependencies other than unix domain sockets.

Security is obviously paramount in a system like this, so a great deal of care should be taken to make sure that certain commands and properties cannot be executed or changed without the appropriate privileges.

# 1.1.3. Privileged Commands and Properties

The idea here is that some commands should be considered "privileged", and actively prevented from letting normal applications access them. This is important if the IPC protocol between the application and the NCP is Spinel.

Examples of such privileged commands would be debugging commands like "peek" or "poke", properties which control bootloader behavior, or changing factory-specified constants. These commands should have some attribute about them that can be easily filtered to prevent applications from using issuing them directly to the NCP.

This would likely be implemented as a part of the renumbering effort (Section 1.1.1).

# 1.2. Property Overview

Spinel is largely a property-based protocol, with a property defined for every attribute that needs to be set, changed, or known by the host. The inspiration of this approach was memory-mapped hardware registers for peripherals. The goal is to avoid, as much as possible, the use of large complicated structures and/or method argument lists. The reason for avoiding these is because they have a tendency to change, especially early in development. Adding or removing a property from a structure can render the entire protocol incompatible. By using properties, you simply change an additional property.

Almost all features and capabilities are implemented using properties. Most new features that are initially proposed as commands can be adapted to be property-based instead. Notable exceptions include "Host Buffer Offload" (Section 9) and "Network Save" (Section 8).

In Spinel, properties are keyed by an unsigned integer between 0 and 2,097,151 (See Section 3.2).

# 1.2.1. Property Methods

Properties may support one or more of the following methods:

- `VALUE_GET`
- `VALUE_SET`
- `VALUE_INSERT`
- `VALUE_REMOVE`

Additionally, the NCP can send updates to the host (either synchronously or asynchronously) that inform the host about changes to specific properties:

- `VALUE_IS`
- `VALUE_INSERTED`
- `VALUE_REMOVED`

# 1.2.2. Property Types

Conceptually, there are three different types of properties:

- Single-value properties
- Multiple-value (Array) properties
- Stream properties

# 1.2.2.1. Single-Value Properties

Single-value properties are properties that have a simple representation of a single value. Examples would be:

- Current radio channel (Represented as a unsigned 8-bit integer)
- Network name (Represented as a UTF-8 encoded string)
- 802.15.4 PAN ID (Represented as a unsigned 16-bit integer)

The valid operations on these sorts of properties are `GET` and `SET`.

# 1.2.2.2. Multiple-Value Properties

Multiple-Value Properties have more than one value associated with them. Examples would be:

- List of channels supported by the radio hardware.
- List of IPv6 addresses assigned to the interface.
- List of capabilities supported by the NCP.

The valid operations on these sorts of properties are `VALUE_GET`, `VALUE_SET`, `VALUE_INSERT`, and `VALUE_REMOVE`.

When the value is fetched using `VALUE_GET`, the returned value is the concatenation of all of the individual values in the list. If the length of the value for an individual item in the list is not defined by the type then each item returned in the list is prepended with a length (See Section 3.5). The order of the returned items, unless explicitly defined for that specific property, is undefined.

`VALUE_SET` provides a way to completely replace all previous values. Calling `VALUE_SET` with an empty value effectively instructs the NCP to clear the value of that property.

`VALUE_INSERT` and `VALUE_REMOVE` provide mechanisms for the insertion or removal of individual items by value. The payload for these commands is a plain single value.

# 1.2.2.3. Stream Properties

Stream properties are special properties representing streams of data. Examples would be:

- Network packet stream (Section 5.3.3)
- Raw packet stream (Section 5.3.2)
- Debug message stream (Section 5.3.1)
- Network Beacon stream (Section 5.5.4)

All such properties emit changes asynchronously using the `VALUE_IS` command, sent from the NCP to the host. For example, as IPv6 traffic is received by the NCP, the IPv6 packets are sent to the host by way of asynchronous `VALUE_IS` notifications.

Some of these properties also support the host send data back to the NCP. For example, this is how the host sends IPv6 traffic to the NCP.

These types of properties generally do not support `VALUE_GET`, as it is meaningless.

# 2. Frame Format

A frame is defined simply as the concatenation of

- A header byte
- A command (up to three bytes, see Section 3.2 for format)
- An optional command payload

Octets: | 1 | 1-3 | n
--- | --- | --- | ---
Fields: | HEADER | CMD | CMD_PAYLOAD

# 2.1. Header Format

The header byte is broken down as follows:

      0   1   2   3   4   5   6   7
    +---+---+---+---+---+---+---+---+
    |  FLG  |  IID  |      TID      |
    +---+---+---+---+---+---+---+---+

[CREF2]RQ: Eventually, when https://github.com/miekg/mmark/issues/95 is addressed, the above table should be swapped out with this: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | |---|---|---|---|---|---|---|---| | FLG || IID || TID ||||

# 2.1.1. FLG: Flag

The flag field of the header byte (`FLG`) is always set to the value two (or `10` in binary). Any frame received with these bits set to any other value else MUST NOT be considered a Spinel frame.

This convention allows Spinel to be line compatible with BTLE HCI. By defining the first two bit in this way we can disambiguate between Spinel frames and HCI frames (which always start with either `0x01` or `0x04`) without any additional framing overhead.

# 2.1.2. IID: Interface Identifier

The Interface Identifier (IID) is a number between 0 and 3 which identifies which subinterface the frame is intended for. This allows the protocol to support connecting to more than one network at once. The first subinterface (0) is considered the primary subinterface and MUST be supported. Support for all other subinterfaces is OPTIONAL.

# 2.1.3. TID: Transaction Identifier

The least significant bits of the header represent the Transaction Identifier(TID). The TID is used for correlating responses to the commands which generated them.

When a command is sent from the host, any reply to that command sent by the NCP will use the same value for the TID. When the host receives a frame that matches the TID of the command it sent, it can easily recognize that frame as the actual response to that command.

The TID value of zero (0) is used for commands to which a correlated response is not expected or needed, such as for unsolicited update commands sent to the host from the NCP.

# 2.1.4. Command Identifier (CMD)

The command identifier is a 21-bit unsigned integer encoded in up to three bytes using the packed unsigned integer format described in Section 3.2. This encoding allows for up to 2,097,152 individual commands, with the first 127 commands represented as a single byte. Command identifiers larger than 2,097,151 are explicitly forbidden.

CID Range | Description
--- | ---
0 - 63 | Reserved for core commands
64 - 15,359 | UNALLOCATED
15,360 - 16,383 | Vendor-specific
16,384 - 1,999,999 | UNALLOCATED
2,000,000 - 2,097,151 | Experimental use only

# 2.1.5. Command Payload (Optional)

Depending on the semantics of the command in question, a payload MAY be included in the frame. The exact composition and length of the payload is defined by the command identifier.

# 3. Data Packing

Data serialization for properties is performed using a light-weight data packing format which was loosely inspired by D-Bus. The format of a serialization is defined by a specially formatted string.

Goals:

- Be lightweight and favor direct representation of values.
- Use an easily readable and memorable format string.
- Support lists and structures.
- Allow properties to be appended to structures while maintaining backward compatibility.

Each primitive datatype has an ASCII character associated with it. Structures can be represented as strings of these characters. For example:

- `C`: A single unsigned byte.
- `C6U`: A single unsigned byte, followed by a 128-bit IPv6 address, followed by a zero-terminated UTF8 string.
- `A(6)`: An array of IPv6 addresses

In each case, the data is represented exactly as described. For example, an array of 10 IPv6 address is stored as 160 bytes.

# 3.1. Primitive Types

Char | Name | Description
--- | --- | ---
`.` | DATATYPE_VOID | Empty data type. Used internally.
`b` | DATATYPE_BOOL | Boolean value. Encoded in 8-bits as either 0x00 or 0x01. All other values are illegal.
`C` | DATATYPE_UINT8 | Unsigned 8-bit integer.
`c` | DATATYPE_INT8 | Signed 8-bit integer.
`S` | DATATYPE_UINT16 | Unsigned 16-bit integer.
`s` | DATATYPE_INT16 | Signed 16-bit integer.
`L` | DATATYPE_UINT32 | Unsigned 32-bit integer.
`l` | DATATYPE_INT32 | Signed 32-bit integer.
`i` | DATATYPE_UINT_PACKED | Packed Unsigned Integer. See Section 3.2.
`6` | DATATYPE_IPv6ADDR | IPv6 Address. (Big-endian)
`E` | DATATYPE_EUI64 | EUI-64 Address. (Big-endian)
`e` | DATATYPE_EUI48 | EUI-48 Address. (Big-endian)
`D` | DATATYPE_DATA | Arbitrary Data. See Section 3.3.
`U` | DATATYPE_UTF8 | Zero-terminated UTF8-encoded string.
`T` | DATATYPE_STRUCT | Structured datatype. Compound type. See Section 3.4.
`A` | DATATYPE_ARRAY | Array of datatypes. Compound type. See Section 3.5.

All multi-byte values are little-endian unless explicitly stated otherwise.

# 3.2. Packed Unsigned Integer

For certain types of integers, such command or property identifiers, usually have a value on the wire that is less than 127. However, in order to not preclude the use of values larger than 255, we would need to add an extra byte. Doing this would add an extra byte to the vast majority of instances, which can add up in terms of bandwidth.

The packed unsigned integer format is based on the unsigned integer format in EXI, except that we limit the maximum value to the largest value that can be encoded into three bytes(2,097,151).

For all values less than 127, the packed form of the number is simply a single byte which directly represents the number. For values larger than 127, the following process is used to encode the value:

1. The unsigned integer is broken up into n 7-bit chunks and placed into n octets, leaving the most significant bit of each octet unused.
2. Order the octets from least-significant to most-significant. (Little-endian)
3. Clear the most significant bit of the most significant octet. Set the least significant bit on all other octets.

Where n is the smallest number of 7-bit chunks you can use to represent the given value.

Take the value 1337, for example:

    1337 => 0x0539
         => [39 0A]
         => [B9 0A]

To decode the value, you collect the 7-bit chunks until you find an octet with the most significant bit clear.

# 3.3. Data Blobs

Data blobs are special datatypes in that the data that they contain does not inherently define the size of the data. This means that if the length of the data blob isn't implied, then the length of the blob must be prepended as a packed unsigned integer.

The length of a data blob is implied only when it is the last datatype in a given buffer. This works because we already know the size of the buffer, and the length of the data is simply the rest of the size of the buffer.

For example, let's say we have a buffer that is encoded with the datatype signature of `CLLD`. In this case, it is pretty easy to tell where the start and end of the data blob is: the start is 9 bytes from the start of the buffer, and its length is the length of the buffer minus 9. (9 is the number of bytes taken up by a byte and two longs)

However, things are a little different with `CLDL`. Since our data blob is no longer the last item in the signature, the length must be prepended.

If you are a little confused, keep reading. This theme comes up in a a few different ways in the following sections.

When a length is prepended, the length is encoded as a little-endian unsigned 16-bit integer.

- Originally the length was a Section 3.2, but it was changed to an unsigned 16-bit integer in order to help reduce protocol requirements.

# 3.4. Structured Data

The structured data type is a way of bundling together a bunch of data into a single data structure. This may at first seem useless. What is the difference between `T(Cii)` and just `Cii`? The answer is, in that particular case, nothing: they are stored in exactly the same way.

However, one case where the structure datatype makes a difference is when you compare `T(Cii)L` to `CiiL`: they end up being represented entirely differently. This is because the structured data type follows the exact same semantics as the data blob type: if it isn't the last datatype in a signature, it must be prepended with a length. This is useful because it allows for new datatypes to be appended to the structure's signature while remaining backward parsing compatibility.

More explicitly, if you take data that was encoded with `T(Cii6)L`, you can still decode it as `T(Cii)L`.

Let's take, for example, the property `PROP_IPv6_ADDR_TABLE`. Conceptually it is just a list of IPv6 addresses, so we can encode it as `A(6c)`. However, if we ever want to associate more data with the type (like flags), we break our backward compatibility if we add another member and use `A(6cC)`. To allow for data to be added without breaking backward compatibility, we use the structured data type from the start: `A(T(6c))`. Then when we add a new member to the structure (`A(T(6cC))`), we don't break backward compatibility.

It's also worth noting that `T(Cii)L` also parses as `DL`. You could then take the resultant data blob and parse it as `Cii`.

When a length is prepended, the length is encoded as a little-endian unsigned 16-bit integer.

# 3.5. Arrays

An array is simply a concatenated set of n data encodings. For example, the type `A(6)` is simply a list of IPv6 addresses---one after the other.

Just like the data blob type and the structured data type, the length of the entire array must be prepended unless the array is the last type in a given signature. Thus, `A(C)` (An array of unsigned bytes) encodes identically to `D`.

When a length is prepended, the length is encoded as a little-endian unsigned 16-bit integer.

# 4. Commands

# 4.1. CMD 0: (Host->NCP) CMD_NOOP

Octets: | 1 | 1
--- | --- | ---
Fields: | HEADER | CMD_NOOP

No-Operation command. Induces the NCP to send a success status back to the host. This is primarily used for liveliness checks.

The command payload for this command SHOULD be empty. The receiver MUST ignore any non-empty command payload.

There is no error condition for this command.

# 4.2. CMD 1: (Host->NCP) CMD_RESET

Octets: | 1 | 1
--- | --- | ---
Fields: | HEADER | CMD_RESET

Reset NCP command. Causes the NCP to perform a software reset. Due to the nature of this command, the TID is ignored. The host should instead wait for a `CMD_PROP_VALUE_IS` command from the NCP indicating `PROP_LAST_STATUS` has been set to `STATUS_RESET_SOFTWARE`.

The command payload for this command SHOULD be empty. The receiver MUST ignore any non-empty command payload.

If an error occurs, the value of `PROP_LAST_STATUS` will be emitted instead with the value set to the generated status code for the error.

# 4.3. CMD 2: (Host->NCP) CMD_PROP_VALUE_GET

Octets: | 1 | 1 | 1-3
--- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_GET | PROP_ID

Get property value command. Causes the NCP to emit a `CMD_PROP_VALUE_IS` command for the given property identifier.

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2.

If an error occurs, the value of `PROP_LAST_STATUS` will be emitted instead with the value set to the generated status code for the error.

# 4.4. CMD 3: (Host->NCP) CMD_PROP_VALUE_SET

Octets: | 1 | 1 | 1-3 | n
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_SET | PROP_ID | VALUE

Set property value command. Instructs the NCP to set the given property to the specific given value, replacing any previous value.

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2, followed by the property value. The exact format of the property value is defined by the property.

If an error occurs, the value of `PROP_LAST_STATUS` will be emitted with the value set to the generated status code for the error.

# 4.5. CMD 4: (Host->NCP) CMD_PROP_VALUE_INSERT

Octets: | 1 | 1 | 1-3 | n
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_INSERT | PROP_ID | VALUE

Insert value into property command. Instructs the NCP to insert the given value into a list-oriented property, without removing other items in the list. The resulting order of items in the list is defined by the individual property being operated on.

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2, followed by the value to be inserted. The exact format of the value is defined by the property.

If an error occurs, the value of `PROP_LAST_STATUS` will be emitted with the value set to the generated status code for the error.

# 4.6. CMD 5: (Host->NCP) CMD_PROP_VALUE_REMOVE

Octets: | 1 | 1 | 1-3 | n
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_REMOVE | PROP_ID | VALUE

Remove value from property command. Instructs the NCP to remove the given value from a list-oriented property, without affecting other items in the list. The resulting order of items in the list is defined by the individual property being operated on.

Note that this command operates by value, not by index!

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2, followed by the value to be removed. The exact format of the value is defined by the property.

If an error occurs, the value of `PROP_LAST_STATUS` will be emitted with the value set to the generated status code for the error.

# 4.7. CMD 6: (NCP->Host) CMD_PROP_VALUE_IS

Octets: | 1 | 1 | 1-3 | n
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_IS | PROP_ID | VALUE

Property value notification command. This command can be sent by the NCP in response to a previous command from the host, or it can be sent by the NCP in an unsolicited fashion to notify the host of various state changes asynchronously.

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2, followed by the current value of the given property.

# 4.8. CMD 7: (NCP->Host) CMD_PROP_VALUE_INSERTED

Octets: | 1 | 1 | 1-3 | n
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_INSERTED | PROP_ID | VALUE

Property value insertion notification command. This command can be sent by the NCP in response to the `CMD_PROP_VALUE_INSERT` command, or it can be sent by the NCP in an unsolicited fashion to notify the host of various state changes asynchronously.

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2, followed by the value that was inserted into the given property.

The resulting order of items in the list is defined by the given property.

# 4.9. CMD 8: (NCP->Host) CMD_PROP_VALUE_REMOVED

Octets: | 1 | 1 | 1-3 | n
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PROP_VALUE_REMOVED | PROP_ID | VALUE

Property value removal notification command. This command can be sent by the NCP in response to the `CMD_PROP_VALUE_REMOVE` command, or it can be sent by the NCP in an unsolicited fashion to notify the host of various state changes asynchronously.

Note that this command operates by value, not by index!

The payload for this command is the property identifier encoded in the packed unsigned integer format described in Section 3.2, followed by the value that was removed from the given property.

The resulting order of items in the list is defined by the given property.

# 4.10. CMD 18: (Host->NCP) CMD_PEEK

Octets: | 1 | 1 | 4 | 2
--- | --- | --- | --- | ---
Fields: | HEADER | CMD_PEEK | ADDRESS | COUNT

This command allows the NCP to fetch values from the RAM of the NCP for debugging purposes. Upon success, `CMD_PEEK_RET` is sent from the NCP to the host. Upon failure, `PROP_LAST_STATUS` is emitted with the appropriate error indication.

Due to the low-level nature of this command, certain error conditions may induce the NCP to reset.

The NCP MAY prevent certain regions of memory from being accessed.

The implementation of this command has security implications. See Section 12 for more information.

This command requires the capability `CAP_PEEK_POKE` to be present.

# 4.11. CMD 19: (NCP->Host) CMD_PEEK_RET

Octets: | 1 | 1 | 4 | 2 | n
--- | --- | --- | --- | --- | ---
Fields: | HEADER | CMD_PEEK_RET | ADDRESS | COUNT | BYTES

This command contains the contents of memory that was requested by a previous call to `CMD_PEEK`.

This command requires the capability `CAP_PEEK_POKE` to be present.

# 4.12. CMD 20: (Host->NCP) CMD_POKE

Octets: | 1 | 1 | 4 | 2 | n
--- | --- | --- | --- | --- | ---
Fields: | HEADER | CMD_POKE | ADDRESS | COUNT | BYTES

This command writes the bytes to the specified memory address for debugging purposes.

Due to the low-level nature of this command, certain error conditions may induce the NCP to reset.

The implementation of this command has security implications. See Section 12 for more information.

This command requires the capability `CAP_PEEK_POKE` to be present.

# 5. Properties

While the majority of the properties that allow the configuration of network connectivity are network protocol specific, there are several properties that are required in all implementations.

Future property allocations SHALL be made from the following allocation plan:

Property ID Range | Description
--- | ---
0 - 127 | Reserved for frequently-used properties
128 - 15,359 | Unallocated
15,360 - 16,383 | Vendor-specific
16,384 - 1,999,999 | Unallocated
2,000,000 - 2,097,151 | Experimental use only

For an explanation of the data format encoding shorthand used throughout this document, see Section 3.

# 5.1. Property Sections

The currently assigned properties are broken up into several sections, each with reserved ranges of property identifiers. These ranges are:

Name | Range (Inclusive) | Documentation
--- | --- | ---
Core | 0x00 - 0x1F, 0x1000 - 0x11FF | Section 5.2
PHY | 0x20 - 0x2F, 0x1200 - 0x12FF | Section 5.4
MAC | 0x30 - 0x3F, 0x1300 - 0x13FF | Section 5.5
NET | 0x40 - 0x4F, 0x1400 - 0x14FF | Section 5.6
Tech | 0x50 - 0x5F, 0x1500 - 0x15FF | Technology-specific
IPv6 | 0x60 - 0x6F, 0x1600 - 0x16FF | Section 5.7
Stream | 0x70 - 0x7F, 0x1700 - 0x17FF | Section 5.2

Note that each property section has two reserved ranges: a primary range (which is encoded as a single byte) and an extended range (which is encoded as two bytes). properties which are used more frequently are generally allocated from the former range.

# 5.2. Core Properties

# 5.2.1. PROP 0: PROP_LAST_STATUS

- Type: Read-Only
- Encoding: `i`

Octets: | 1-3
--- | ---
Fields: | LAST_STATUS

Describes the status of the last operation. Encoded as a packed unsigned integer.

This property is emitted often to indicate the result status of pretty much any Host-to-NCP operation.

It is emitted automatically at NCP startup with a value indicating the reset reason.

See Section 6 for the complete list of status codes.

# 5.2.2. PROP 1: PROP_PROTOCOL_VERSION

- Type: Read-Only
- Encoding: `ii`

Octets: | 1-3 | 1-3
--- | --- | ---
Fields: | MAJOR_VERSION | MINOR_VERSION

Describes the protocol version information. This property contains four fields, each encoded as a packed unsigned integer:

- Major Version Number
- Minor Version Number

This document describes major version 4, minor version 1 of this protocol.

# 5.2.2.1. Major Version Number

The major version number is used to identify large and incompatible differences between protocol versions.

The host MUST enter a FAULT state if it does not explicitly support the given major version number.

# 5.2.2.2. Minor Version Number

The minor version number is used to identify small but otherwise compatible differences between protocol versions. A mismatch between the advertised minor version number and the minor version that is supported by the host SHOULD NOT be fatal to the operation of the host.

# 5.2.3. PROP 2: PROP_NCP_VERSION

- Type: Read-Only
- Packed-Encoding: `U`

Octets: | n
--- | ---
Fields: | NCP_VESION_STRING

Contains a string which describes the firmware currently running on the NCP. Encoded as a zero-terminated UTF-8 string.

The format of the string is not strictly defined, but it is intended to present similarly to the "User-Agent" string from HTTP. The RECOMMENDED format of the string is as follows:

    STACK-NAME/STACK-VERSION[BUILD_INFO][; OTHER_INFO]; BUILD_DATE_AND_TIME

Examples:

- `OpenThread/1.0d26-25-gb684c7f; DEBUG; May 9 2016 18:22:04`
- `ConnectIP/2.0b125 s1 ALPHA; Sept 24 2015 20:49:19`

# 5.2.4. PROP 3: PROP_INTERFACE_TYPE

- Type: Read-Only
- Encoding: `i`

Octets: | 1-3
--- | ---
Fields: | INTERFACE_TYPE

This integer identifies what the network protocol for this NCP. Currently defined values are:

- 0: Bootloader
- 2: ZigBeeIP
- 3: Thread

The host MUST enter a FAULT state if it does not recognize the protocol given by the NCP.

# 5.2.5. PROP 4: PROP_INTERFACE_VENDOR_ID

- Type: Read-Only
- Encoding: `i`

Octets: | 1-3
--- | ---
Fields: | VENDOR_ID

Vendor identifier.

# 5.2.6. PROP 5: PROP_CAPS

- Type: Read-Only
- Packed-Encoding: `A(i)`

Octets: | 1-3 | 1-3 | ...
--- | --- | --- | ---
Fields: | CAP_1 | CAP_2 | ...

Describes the supported capabilities of this NCP. Encoded as a list of packed unsigned integers.

A capability is defined as a 21-bit integer that describes a subset of functionality which is supported by the NCP.

Currently defined values are:

- 1: `CAP_LOCK`
- 2: `CAP_NET_SAVE`
- 3: `CAP_HBO`: Host Buffer Offload. See Section 9.
- 4: `CAP_POWER_SAVE`
- 5: `CAP_COUNTERS`
- 6: `CAP_JAM_DETECT`: Jamming detection. See Section 10
- 7: `CAP_PEEK_POKE`: PEEK/POKE debugging commands.
- 8: `CAP_WRITABLE_RAW_STREAM`: `PROP_STREAM_RAW` is writable.
- 9: `CAP_GPIO`: Support for GPIO access. See Section 11.
- 16: `CAP_802_15_4_2003`
- 17: `CAP_802_15_4_2006`
- 18: `CAP_802_15_4_2011`
- 21: `CAP_802_15_4_PIB`
- 24: `CAP_802_15_4_2450MHZ_OQPSK`
- 25: `CAP_802_15_4_915MHZ_OQPSK`
- 26: `CAP_802_15_4_868MHZ_OQPSK`
- 27: `CAP_802_15_4_915MHZ_BPSK`
- 28: `CAP_802_15_4_868MHZ_BPSK`
- 29: `CAP_802_15_4_915MHZ_ASK`
- 30: `CAP_802_15_4_868MHZ_ASK`
- 48: `CAP_ROLE_ROUTER`
- 49: `CAP_ROLE_SLEEPY`
- 52: `CAP_NET_THREAD_1_0`
- 512: `CAP_MAC_WHITELIST`

Additionally, future capability allocations SHALL be made from the following allocation plan:

Capability Range | Description
--- | ---
0 - 127 | Reserved for core capabilities
128 - 15,359 | UNALLOCATED
15,360 - 16,383 | Vendor-specific
16,384 - 1,999,999 | UNALLOCATED
2,000,000 - 2,097,151 | Experimental use only

# 5.2.7. PROP 6: PROP_INTERFACE_COUNT

- Type: Read-Only
- Packed-Encoding: `C`

Octets: | 1
--- | ---
Fields: | `INTERFACE_COUNT`

Describes the number of concurrent interfaces supported by this NCP. Since the concurrent interface mechanism is still TBD, this value MUST always be one.

This value is encoded as an unsigned 8-bit integer.

# 5.2.8. PROP 7: PROP_POWER_STATE

- Type: Read-Write
- Packed-Encoding: `C`

Octets: | 1
--- | ---
Fields: | POWER_STATE

Describes the current power state of the NCP. By writing to this property you can manage the lower state of the NCP. Enumeration is encoded as a single unsigned byte.

Defined values are:

- 0: `POWER_STATE_OFFLINE`: NCP is physically powered off. (Enumerated for completeness sake, not expected on the wire)
- 1: `POWER_STATE_DEEP_SLEEP`: Almost everything on the NCP is shut down, but can still be resumed via a command or interrupt.
- 2: `POWER_STATE_STANDBY`: NCP is in the lowest power state that can still be awoken by an event from the radio (e.g. waiting for alarm)
- 3: `POWER_STATE_LOW_POWER`: NCP is responsive (and possibly connected), but using less power. (e.g. "Sleepy" child node)
- 4: `POWER_STATE_ONLINE`: NCP is fully powered. (e.g. "Parent" node)

# 5.2.9. PROP 8: PROP_HWADDR

- Type: Read-Only*
- Packed-Encoding: `E`

Octets: | 8
--- | ---
Fields: | HWADDR

The static EUI64 address of the device, used as a serial number. This value is read-only, but may be writable under certain vendor-defined circumstances.

# 5.2.10. PROP 9: PROP_LOCK

- Type: Read-Write
- Packed-Encoding: `b`

Octets: | 1
--- | ---
Fields: | LOCK

Property lock. Used for grouping changes to several properties to take effect at once, or to temporarily prevent the automatic updating of property values. When this property is set, the execution of the NCP is effectively frozen until it is cleared.

This property is only supported if the `CAP_LOCK` capability is present.

Unlike most other properties, setting this property to true when the value of the property is already true MUST fail with a last status of `STATUS_ALREADY`.

# 5.3. Stream Properties

# 5.3.1. PROP 112: PROP_STREAM_DEBUG

- Type: Read-Only-Stream
- Packed-Encoding: `U`

Octets: | n
--- | ---
Fields: | UTF8_DATA

This property is a streaming property, meaning that you cannot explicitly fetch the value of this property. The stream provides human-readable debugging output which may be displayed in the host logs.

The location of newline characters is not assumed by the host: it is the NCP's responsibility to insert newline characters where needed, just like with any other text stream.

To receive the debugging stream, you wait for `CMD_PROP_VALUE_IS` commands for this property from the NCP.

# 5.3.2. PROP 113: PROP_STREAM_RAW

- Type: Read-Write-Stream
- Packed-Encoding: `DD`

Octets: | 2 | n | n
--- | --- | --- | ---
Fields: | FRAME_DATA_LEN | FRAME_DATA | FRAME_METADATA

This stream provides the capability of sending and receiving raw packets to and from the radio. The exact format of the frame metadata and data is dependent on the MAC and PHY being used.

This property is a streaming property, meaning that you cannot explicitly fetch the value of this property. To receive traffic, you wait for `CMD_PROP_VALUE_IS` commands with this property id from the NCP.

Implementations may OPTIONALLY support the ability to transmit arbitrary raw packets. Support for this feature is indicated by the presence of the `CAP_WRITABLE_RAW_STREAM` capability.

If the capability `CAP_WRITABLE_RAW_STREAM` is set, then packets written to this stream with `CMD_PROP_VALUE_SET` will be sent out over the radio. This allows the caller to use the radio directly, with the stack being implemented on the host instead of the NCP.

# 5.3.2.1. Frame Metadata Format

Any data past the end of `FRAME_DATA_LEN` is considered metadata and is OPTIONAL. Frame metadata MAY be empty or partially specified. Partially specified metadata MUST be accepted. Default values are used for all unspecified fields.

The same general format is used for `PROP_STREAM_RAW`, `PROP_STREAM_NET`, and `PROP_STREAM_NET_INSECURE`. It can be used for frames sent from the NCP to the host as well as frames sent from the host to the NCP.

The frame metadata field consists of the following fields:

Field | Description | Type | Len | Default
--- | --- | --- | --- | ---
MD_POWER | (dBm) RSSI/TX-Power | `c` int8 | 1 | -128
MD_NOISE | (dBm) Noise floor | `c` int8 | 1 | -128
MD_FLAG | Flags (defined below) | `S` uint16 | 2 |
MD_PHY | PHY-specific data | `D` data | >=2 |
MD_VEND | Vendor-specific data | `D` data | >=2 |

The following fields are ignored by the NCP for packets sent to it from the host:

- MD_NOISE
- MD_FLAG

When specifying `MD_POWER` for a packet to be transmitted, the actual transmit power is never larger than the current value of `PROP_PHY_TX_POWER` (Section 5.4.6). When left unspecified (or set to the value -128), an appropriate transmit power will be chosen by the NCP.

The bit values in `MD_FLAG` are defined as follows:

Bit | Mask | Name | Description if set
--- | --- | --- | ---
15 | 0x0001 | MD_FLAG_TX | Packet was transmitted, not received.
13 | 0x0004 | MD_FLAG_BAD_FCS | Packet was received with bad FCS
12 | 0x0008 | MD_FLAG_DUPE | Packet seems to be a duplicate
0-11, 14 | 0xFFF2 | MD_FLAG_RESERVED | Flags reserved for future use.

The format of `MD_PHY` is specified by the PHY layer currently in use, and may contain information such as the channel, LQI, antenna, or other pertainent information.

# 5.3.3. PROP 114: PROP_STREAM_NET

- Type: Read-Write-Stream
- Packed-Encoding: `DD`

Octets: | 2 | n | n
--- | --- | --- | ---
Fields: | FRAME_DATA_LEN | FRAME_DATA | FRAME_METADATA

This stream provides the capability of sending and receiving data packets to and from the currently attached network. The exact format of the frame metadata and data is dependent on the network protocol being used.

This property is a streaming property, meaning that you cannot explicitly fetch the value of this property. To receive traffic, you wait for `CMD_PROP_VALUE_IS` commands with this property id from the NCP.

To send network packets, you call `CMD_PROP_VALUE_SET` on this property with the value of the packet.

Any data past the end of `FRAME_DATA_LEN` is considered metadata, the format of which is described in Section 5.3.2.1.

# 5.3.4. PROP 114: PROP_STREAM_NET_INSECURE

- Type: Read-Write-Stream
- Packed-Encoding: `DD`

Octets: | 2 | n | n
--- | --- | --- | ---
Fields: | FRAME_DATA_LEN | FRAME_DATA | FRAME_METADATA

This stream provides the capability of sending and receiving unencrypted and unauthenticated data packets to and from nearby devices for the purposes of device commissioning. The exact format of the frame metadata and data is dependent on the network protocol being used.

This property is a streaming property, meaning that you cannot explicitly fetch the value of this property. To receive traffic, you wait for `CMD_PROP_VALUE_IS` commands with this property id from the NCP.

To send network packets, you call `CMD_PROP_VALUE_SET` on this property with the value of the packet.

Any data past the end of `FRAME_DATA_LEN` is considered metadata, the format of which is described in Section 5.3.2.1.

# 5.4. PHY Properties

# 5.4.1. PROP 32: PROP_PHY_ENABLED

- Type: Read-Write
- Packed-Encoding: `b` (bool8)

Set to 1 if the PHY is enabled, set to 0 otherwise. May be directly enabled to bypass higher-level packet processing in order to implement things like packet sniffers.

# 5.4.2. PROP 33: PROP_PHY_CHAN

- Type: Read-Write
- Packed-Encoding: `C` (uint8)

Value is the current channel. Must be set to one of the values contained in `PROP_PHY_CHAN_SUPPORTED`.

# 5.4.3. PROP 34: PROP_PHY_CHAN_SUPPORTED

- Type: Read-Only
- Packed-Encoding: `A(C)` (array of uint8)
- Unit: List of channels

Value is a list of channel values that are supported by the hardware.

# 5.4.4. PROP 35: PROP_PHY_FREQ

- Type: Read-Only
- Packed-Encoding: `L` (uint32)
- Unit: Kilohertz

Value is the radio frequency (in kilohertz) of the current channel.

# 5.4.5. PROP 36: PROP_PHY_CCA_THRESHOLD

- Type: Read-Write
- Packed-Encoding: `c` (int8)
- Unit: dBm

Value is the CCA (clear-channel assessment) threshold. Set to -128 to disable.

When setting, the value will be rounded down to a value that is supported by the underlying radio hardware.

# 5.4.6. PROP 37: PROP_PHY_TX_POWER

- Type: Read-Write
- Packed-Encoding: `c` (int8)
- Unit: dBm

Value is the transmit power of the radio.

When setting, the value will be rounded down to a value that is supported by the underlying radio hardware.

# 5.4.7. PROP 38: PROP_PHY_RSSI

- Type: Read-Only
- Packed-Encoding: `c` (int8)
- Unit: dBm

Value is the current RSSI (Received signal strength indication) from the radio. This value can be used in energy scans and for determining the ambient noise floor for the operating environment.

# 5.5. MAC Properties

# 5.5.1. PROP 48: PROP_MAC_SCAN_STATE

- Type: Read-Write
- Packed-Encoding: `C`
- Unit: Enumeration

Possible Values:

- 0: `SCAN_STATE_IDLE`
- 1: `SCAN_STATE_BEACON`
- 2: `SCAN_STATE_ENERGY`

Set to `SCAN_STATE_BEACON` to start an active scan. Beacons will be emitted from `PROP_MAC_SCAN_BEACON`.

Set to `SCAN_STATE_ENERGY` to start an energy scan. Channel energy will be reported by alternating emissions of `PROP_PHY_CHAN` and `PROP_PHY_RSSI`.

Values switches to `SCAN_STATE_IDLE` when scan is complete.

# 5.5.2. PROP 49: PROP_MAC_SCAN_MASK

- Type: Read-Write
- Packed-Encoding: `A(C)`
- Unit: List of channels to scan

# 5.5.3. PROP 50: PROP_MAC_SCAN_PERIOD

- Type: Read-Write
- Packed-Encoding: `S` (uint16)
- Unit: milliseconds per channel

# 5.5.4. PROP 51: PROP_MAC_SCAN_BEACON

- Type: Read-Only-Stream
- Packed-Encoding: `CcDD.` (or `CcT(ESSc.)T(iCUD.).`)

Octets: | 1 | 1 | 2 | n | 2 | n
--- | --- | --- | --- | --- | --- | ---
Fields: | CH | RSSI | MAC_LEN | MAC_DATA | NET_LEN | NET_DATA

Scan beacons have two embedded structures which contain information about the MAC layer and the NET layer. Their format depends on the MAC and NET layer currently in use. The format below is for an 802.15.4 MAC with Thread:

- `C`: Channel
- `c`: RSSI of the beacon
- `T`: MAC layer properties
  - `E`: Long address
  - `S`: Short address
  - `S`: PAN-ID
  - `c`: LQI
- `T`: NET layer properties
  - `i`: Protocol Number
  - `C`: Flags
  - `U`: Network Name
  - `D`: XPANID

Extra parameters may be added to each of the structures in the future, so care should be taken to read the length that prepends each structure.

# 5.5.5. PROP 52: PROP_MAC_15_4_LADDR

- Type: Read-Write
- Packed-Encoding: `E`

The 802.15.4 long address of this node.

This property is only present on NCPs which implement 802.15.4

# 5.5.6. PROP 53: PROP_MAC_15_4_SADDR

- Type: Read-Write
- Packed-Encoding: `S`

The 802.15.4 short address of this node.

This property is only present on NCPs which implement 802.15.4

# 5.5.7. PROP 54: PROP_MAC_15_4_PANID

- Type: Read-Write
- Packed-Encoding: `S`

The 802.15.4 PANID this node is associated with.

This property is only present on NCPs which implement 802.15.4

# 5.5.8. PROP 55: PROP_MAC_RAW_STREAM_ENABLED

- Type: Read-Write
- Packed-Encoding: `b`

Set to true to enable raw MAC frames to be emitted from `PROP_STREAM_RAW`. See Section 5.3.2.

# 5.5.9. PROP 56: PROP_MAC_PROMISCUOUS_MODE

- Type: Read-Write
- Packed-Encoding: `C`

Possible Values:

Id | Name | Description
--- | --- | ---
0 | `MAC_PROMISCUOUS_MODE_OFF` | Normal MAC filtering is in place.
1 | `MAC_PROMISCUOUS_MODE_NETWORK` | All MAC packets matching network are passed up the stack.
2 | `MAC_PROMISCUOUS_MODE_FULL` | All decoded MAC packets are passed up the stack.

See Section 5.3.2.

# 5.5.10. PROP 4864: PROP_MAC_WHITELIST

- Type: Read-Write
- Packed-Encoding: `A(T(Ec))`
- OPTIONAL

Structure Parameters:

- `E`: EUI64 address of node
- `c`: Optional RSSI-override value. The value 127 indicates that the RSSI-override feature is not enabled for this address. If this value is omitted when setting or inserting, it is assumed to be 127. This parameter is ignored when removing.

# 5.5.11. PROP 4865: PROP_MAC_WHITELIST_ENABLED

- Type: Read-Write
- Packed-Encoding: `b`

# 5.6. NET Properties

# 5.6.1. PROP 64: PROP_NET_SAVED

- Type: Read-Only
- Packed-Encoding: `b`

Returns true if there is a network state stored that can be restored with a call to `CMD_NET_RECALL`.

# 5.6.2. PROP 65: PROP_NET_IF_UP

- Type: Read-Write
- Packed-Encoding: `b`

Network interface up/down status. Non-zero (set to 1) indicates up, zero indicates down.

# 5.6.3. PROP 66: PROP_NET_STACK_UP

- Type: Read-Write
- Packed-Encoding: `b`
- Unit: Enumeration

Thread stack operational status. Non-zero (set to 1) indicates up, zero indicates down.

# 5.6.4. PROP 67: PROP_NET_ROLE

- Type: Read-Write
- Packed-Encoding: `C`
- Unit: Enumeration

Values:

- 0: `NET_ROLE_DETACHED`
- 1: `NET_ROLE_CHILD`
- 2: `NET_ROLE_ROUTER`
- 3: `NET_ROLE_LEADER`

# 5.6.5. PROP 68: PROP_NET_NETWORK_NAME

- Type: Read-Write
- Packed-Encoding: `U`

# 5.6.6. PROP 69: PROP_NET_XPANID

- Type: Read-Write
- Packed-Encoding: `D`

# 5.6.7. PROP 70: PROP_NET_MASTER_KEY

- Type: Read-Write
- Packed-Encoding: `D`

# 5.6.8. PROP 71: PROP_NET_KEY_SEQUENCE_COUNTER

- Type: Read-Write
- Packed-Encoding: `L`

# 5.6.9. PROP 72: PROP_NET_PARTITION_ID

- Type: Read-Write
- Packed-Encoding: `L`

The partition ID of the partition that this node is a member of.

# 5.6.10. PROP 73: PROP_NET_KEY_SWITCH_GUARDTIME

- Type: Read-Write
- Packed-Encoding: `L`

# 5.7. IPv6 Properties

# 5.7.1. PROP 96: PROP_IPV6_LL_ADDR

- Type: Read-Only
- Packed-Encoding: `6`

IPv6 Address

# 5.7.2. PROP 97: PROP_IPV6_ML_ADDR

- Type: Read-Only
- Packed-Encoding: `6`

IPv6 Address + Prefix Length

# 5.7.3. PROP 98: PROP_IPV6_ML_PREFIX

- Type: Read-Write
- Packed-Encoding: `6C`

IPv6 Prefix + Prefix Length

# 5.7.4. PROP 99: PROP_IPV6_ADDRESS_TABLE

- Type: Read-Write
- Packed-Encoding: `A(T(6CLLC))`

Array of structures containing:

- `6`: IPv6 Address
- `C`: Network Prefix Length
- `L`: Valid Lifetime
- `L`: Preferred Lifetime
- `C`: Flags

# 5.7.5. PROP 101: PROP_IPv6_ICMP_PING_OFFLOAD

- Type: Read-Write
- Packed-Encoding: `b`

Allow the NCP to directly respond to ICMP ping requests. If this is turned on, ping request ICMP packets will not be passed to the host.

Default value is `false`.

# 6. Status Codes

Status codes are sent from the NCP to the host via `PROP_LAST_STATUS` using the `CMD_VALUE_IS` command to indicate the return status of a previous command. As with any response, the TID field of the FLAG byte is used to correlate the response with the request.

Note that most successfully executed commands do not indicate a last status of `STATUS_OK`. The usual way the NCP indicates a successful command is to mirror the property change back to the host. For example, if you do a `CMD_VALUE_SET` on `PROP_PHY_ENABLED`, the NCP would indicate success by responding with a `CMD_VALUE_IS` for `PROP_PHY_ENABLED`. If the command failed, `PROP_LAST_STATUS` would be emitted instead.

See Section 5.2.1 for more information on `PROP_LAST_STATUS`.

- 0: `STATUS_OK`: Operation has completed successfully.
- 1: `STATUS_FAILURE`: Operation has failed for some undefined reason.
- 2: `STATUS_UNIMPLEMENTED`: The given operation has not been implemented.
- 3: `STATUS_INVALID_ARGUMENT`: An argument to the given operation is invalid.
- 4: `STATUS_INVALID_STATE` : The given operation is invalid for the current state of the device.
- 5: `STATUS_INVALID_COMMAND`: The given command is not recognized.
- 6: `STATUS_INVALID_INTERFACE`: The given Spinel interface is not supported.
- 7: `STATUS_INTERNAL_ERROR`: An internal runtime error has occurred.
- 8: `STATUS_SECURITY_ERROR`: A security or authentication error has occurred.
- 9: `STATUS_PARSE_ERROR`: An error has occurred while parsing the command.
- 10: `STATUS_IN_PROGRESS`: The operation is in progress and will be completed asynchronously.
- 11: `STATUS_NOMEM`: The operation has been prevented due to memory pressure.
- 12: `STATUS_BUSY`: The device is currently performing a mutually exclusive operation.
- 13: `STATUS_PROP_NOT_FOUND`: The given property is not recognized.
- 14: `STATUS_PACKET_DROPPED`: The packet was dropped.
- 15: `STATUS_EMPTY`: The result of the operation is empty.
- 16: `STATUS_CMD_TOO_BIG`: The command was too large to fit in the internal buffer.
- 17: `STATUS_NO_ACK`: The packet was not acknowledged.
- 18: `STATUS_CCA_FAILURE`: The packet was not sent due to a CCA failure.
- 19: `STATUS_ALREADY`: The operation is already in progress or the property was already set to the given value.
- 20: `STATUS_ITEM_NOT_FOUND`: The given item could not be found in the property.
- 21-111: RESERVED
- 112-127: Reset Causes
  - 112: `STATUS_RESET_POWER_ON`
  - 113: `STATUS_RESET_EXTERNAL`
  - 114: `STATUS_RESET_SOFTWARE`
  - 115: `STATUS_RESET_FAULT`
  - 116: `STATUS_RESET_CRASH`
  - 117: `STATUS_RESET_ASSERT`
  - 118: `STATUS_RESET_OTHER`
  - 119: `STATUS_RESET_UNKNOWN`
  - 120: `STATUS_RESET_WATCHDOG`
  - 121-127: RESERVED-RESET-CODES
- 128 - 15,359: UNALLOCATED
- 15,360 - 16,383: Vendor-specific
- 16,384 - 1,999,999: UNALLOCATED
- 2,000,000 - 2,097,151: Experimental Use Only (MUST NEVER be used in production!)

# 7. Technology: Thread

This section describes all of the properties and semantics required for managing a Thread NCP.

Thread NCPs have the following requirements:

- The property `PROP_INTERFACE_TYPE` must be 3.
- The non-optional properties in the following sections MUST be implemented: CORE, PHY, MAC, NET, and IPV6.

All serious implementations of an NCP SHOULD also support the network save feature (See Section 8).

# 7.1. Thread Capabilities

The Thread technology defines the following capabilities:

- `CAP_NET_THREAD_1_0` - Indicates that the NCP implements v1.0 of the Thread standard.
- `CAP_NET_THREAD_1_1` - Indicates that the NCP implements v1.1 of the Thread standard.

# 7.2. Thread Properties

Properties for Thread are allocated out of the `Tech` property section (see Section 5.1).

# 7.2.1. PROP 80: PROP_THREAD_LEADER_ADDR

- Type: Read-Only
- Packed-Encoding: `6`

The IPv6 address of the leader. (Note: May change to long and short address of leader)

# 7.2.2. PROP 81: PROP_THREAD_PARENT

- Type: Read-Only
- Packed-Encoding: `ES`
- LADDR, SADDR

The long address and short address of the parent of this node.

# 7.2.3. PROP 82: PROP_THREAD_CHILD_TABLE

- Type: Read-Only
- Packed-Encoding: `A(T(ES))`

Table containing the long and short addresses of all the children of this node.

# 7.2.4. PROP 83: PROP_THREAD_LEADER_RID

- Type: Read-Only
- Packed-Encoding: `C`

The router-id of the current leader.

# 7.2.5. PROP 84: PROP_THREAD_LEADER_WEIGHT

- Type: Read-Only
- Packed-Encoding: `C`

The leader weight of the current leader.

# 7.2.6. PROP 85: PROP_THREAD_LOCAL_LEADER_WEIGHT

- Type: Read-Write
- Packed-Encoding: `C`

The leader weight for this node.

# 7.2.7. PROP 86: PROP_THREAD_NETWORK_DATA

- Type: Read-Only
- Packed-Encoding: `D`

# 7.2.8. PROP 87: PROP_THREAD_NETWORK_DATA_VERSION

- Type: Read-Only
- Packed-Encoding: `S`

# 7.2.9. PROP 88: PROP_THREAD_STABLE_NETWORK_DATA

- Type: Read-Only
- Packed-Encoding: `D`

# 7.2.10. PROP 89: PROP_THREAD_STABLE_NETWORK_DATA_VERSION

- Type: Read-Only
- Packed-Encoding: `S`

# 7.2.11. PROP 90: PROP_THREAD_ON_MESH_NETS

- Type: Read-Write
- Packed-Encoding: `A(T(6CbCb))`

Data per item is:

- `6`: IPv6 Prefix
- `C`: Prefix length, in bits
- `b`: Stable flag
- `C`: Thread flags
- `b`: "Is defined locally" flag. Set if this network was locally defined. Assumed to be true for set, insert and replace. Clear if the on mesh network was defined by another node.

# 7.2.12. PROP 91: PROP_THREAD_LOCAL_ROUTES

- Type: Read-Write
- Packed-Encoding: `A(T(6CbC))`

Data per item is:

- `6`: IPv6 Prefix
- `C`: Prefix length, in bits
- `b`: Stable flag
- `C`: Other flags

# 7.2.13. PROP 92: PROP_THREAD_ASSISTING_PORTS

- Type: Read-Write
- Packed-Encoding: `A(S)`

# 7.2.14. PROP 93: PROP_THREAD_ALLOW_LOCAL_NET_DATA_CHANGE

- Type: Read-Write
- Packed-Encoding: `b`

Set to true before changing local net data. Set to false when finished. This allows changes to be aggregated into single events.

# 7.2.15. PROP 94: PROP_THREAD_MODE

- Type: Read-Write
- Packed-Encoding: `C`

This property contains the value of the mode TLV for this node. The meaning of the bits in this bitfield are defined by section 4.5.2 of the Thread specification.

# 7.2.16. PROP 5376: PROP_THREAD_CHILD_TIMEOUT

- Type: Read-Write
- Packed-Encoding: `L`

Used when operating in the Child role.

# 7.2.17. PROP 5377: PROP_THREAD_RLOC16

- Type: Read-Write
- Packed-Encoding: `S`

# 7.2.18. PROP 5378: PROP_THREAD_ROUTER_UPGRADE_THRESHOLD

- Type: Read-Write
- Packed-Encoding: `C`

# 7.2.19. PROP 5379: PROP_THREAD_CONTEXT_REUSE_DELAY

- Type: Read-Write
- Packed-Encoding: `L`

# 7.2.20. PROP 5380: PROP_THREAD_NETWORK_ID_TIMEOUT

- Type: Read-Write
- Packed-Encoding: `C`

Allows you to get or set the Thread `NETWORK_ID_TIMEOUT` constant, as defined by the Thread specification.

# 7.2.21. PROP 5381: PROP_THREAD_ACTIVE_ROUTER_IDS

- Type: Read-Write/Write-Only
- Packed-Encoding: `A(C)` (List of active thread router ids)

Note that some implementations may not support `CMD_GET_VALUE` router ids, but may support `CMD_REMOVE_VALUE` when the node is a leader.

# 7.2.22. PROP 5382: PROP_THREAD_RLOC16_DEBUG_PASSTHRU

- Type: Read-Write
- Packed-Encoding: `b`

Allow the HOST to directly observe all IPv6 packets received by the NCP, including ones sent to the RLOC16 address.

Default value is `false`.

# 7.2.23. PROP 5383: SPINEL_PROP_THREAD_ROUTER_ROLE_ENABLED

- Type: Read-Write
- Packed-Encoding: `b`

Allow the HOST to indicate whether or not the router role is enabled. If current role is a router, setting this property to `false` starts a re-attach process as an end-device.

# 7.2.24. PROP 5384: PROP_THREAD_ROUTER_DOWNGRADE_THRESHOLD

- Type: Read-Write
- Packed-Encoding: `C`

# 7.2.25. PROP 5385: PROP_THREAD_ROUTER_SELECTION_JITTER

- Type: Read-Write
- Packed-Encoding: `C`

Specifies the self imposed random delay in seconds a REED waits before registering to become an Active Router.

# 7.2.26. PROP 5386: PROP_THREAD_PREFERRED_ROUTER_ID

- Type: Write-Only
- Packed-Encoding: `C`

Specifies the preferred Router Id. Upon becoming a router/leader the node attempts to use this Router Id. If the preferred Router Id is not set or if it can not be used, a randomly generated router id is picked. This property can be set only when the device role is either detached or disabled.

# 7.2.27. PROP 5387: SPINEL_PROP_THREAD_NEIGHBOR_TABLE

- Type: Read-Only
- Packed-Encoding: `A(T(ESLCcCbLL))`

Data per item is:

- `E`: Extended/long address
- `S`: RLOC16
- `L`: Age
- `C`: Link Quality In
- `c`: Average RSS
- `C`: Mode (bit-flags)
- `b`: `true` if neighbor is a child, `false` otherwise.
- `L`: Link Frame Counter
- `L`: MLE Frame Counter

# 8. Feature: Network Save

The network save feature is an optional NCP capability that, when present, allows the host to save and recall network credentials and state to and from nonvolatile storage.

The presence of this feature can be detected by checking for the presence of the `CAP_NET_SAVE` capability in `PROP_CAPS`.

# 8.1. Commands

# 8.1.1. CMD 9: (Host->NCP) CMD_NET_SAVE

Octets: | 1 | 1
--- | --- | ---
Fields: | HEADER | CMD_NET_SAVE

Save network state command. Saves any current network credentials and state necessary to reconnect to the current network to non-volatile memory.

This operation affects non-volatile memory only. The current network information stored in volatile memory is unaffected.

The response to this command is always a `CMD_PROP_VALUE_IS` for `PROP_LAST_STATUS`, indicating the result of the operation.

This command is only available if the `CAP_NET_SAVE` capability is set.

# 8.1.2. CMD 10: (Host->NCP) CMD_NET_CLEAR

Octets: | 1 | 1
--- | --- | ---
Fields: | HEADER | CMD_NET_CLEAR

Clear saved network state command. Clears any previously saved network credentials and state previously stored by `CMD_NET_SAVE` from non-volatile memory.

This operation affects non-volatile memory only. The current network information stored in volatile memory is unaffected.

The response to this command is always a `CMD_PROP_VALUE_IS` for `PROP_LAST_STATUS`, indicating the result of the operation.

This command is only available if the `CAP_NET_SAVE` capability is set.

# 8.1.3. CMD 11: (Host->NCP) CMD_NET_RECALL

Octets: | 1 | 1
--- | --- | ---
Fields: | HEADER | CMD_NET_RECALL

Recall saved network state command. Recalls any previously saved network credentials and state previously stored by `CMD_NET_SAVE` from non-volatile memory.

This command will typically generated several unsolicited property updates as the network state is loaded. At the conclusion of loading, the authoritative response to this command is always a `CMD_PROP_VALUE_IS` for `PROP_LAST_STATUS`, indicating the result of the operation.

This command is only available if the `CAP_NET_SAVE` capability is set.

# 9. Feature: Host Buffer Offload

The memory on an NCP may be much more limited than the memory on the host processor. In such situations, it is sometimes useful for the NCP to offload buffers to the host processor temporarily so that it can perform other operations.

Host buffer offload is an optional NCP capability that, when present, allows the NCP to store data buffers on the host processor that can be recalled at a later time.

The presence of this feature can be detected by the host by checking for the presence of the `CAP_HBO` capability in `PROP_CAPS`.

# 9.1. Commands

# 9.1.1. CMD 12: (NCP->Host) CMD_HBO_OFFLOAD

- Argument-Encoding: `LscD`
  - `OffloadId`: 32-bit unique block identifier
  - `Expiration`: In seconds-from-now
  - `Priority`: Critical, High, Medium, Low
  - `Data`: Data to offload

# 9.1.2. CMD 13: (NCP->Host) CMD_HBO_RECLAIM

- Argument-Encoding: `Lb`
  - `OffloadId`: 32-bit unique block identifier
  - `KeepAfterReclaim`: If not set to true, the block will be dropped by the host after it is sent to the NCP.

# 9.1.3. CMD 14: (NCP->Host) CMD_HBO_DROP

- Argument-Encoding: `L`
  - `OffloadId`: 32-bit unique block identifier

# 9.1.4. CMD 15: (Host->NCP) CMD_HBO_OFFLOADED

- Argument-Encoding: `Li`
  - `OffloadId`: 32-bit unique block identifier
  - `Status`: Status code for the result of the operation.

# 9.1.5. CMD 16: (Host->NCP) CMD_HBO_RECLAIMED

- Argument-Encoding: `LiD`
  - `OffloadId`: 32-bit unique block identifier
  - `Status`: Status code for the result of the operation.
  - `Data`: Data that was previously offloaded (if any)

# 9.1.6. CMD 17: (Host->NCP) CMD_HBO_DROPPED

- Argument-Encoding: `Li`
  - `OffloadId`: 32-bit unique block identifier
  - `Status`: Status code for the result of the operation.

# 9.2. Properties

# 9.2.1. PROP 10: PROP_HBO_MEM_MAX

- Type: Read-Write
- Packed-Encoding: `L`

Octets: | 4
--- | ---
Fields: | `PROP_HBO_MEM_MAX`

Describes the number of bytes that may be offloaded from the NCP to the host. Default value is zero, so this property must be set by the host to a non-zero value before the NCP will begin offloading blocks.

This value is encoded as an unsigned 32-bit integer.

This property is only available if the `CAP_HBO` capability is present in `PROP_CAPS`.

# 9.2.2. PROP 11: PROP_HBO_BLOCK_MAX

- Type: Read-Write
- Packed-Encoding: `S`

Octets: | 2
--- | ---
Fields: | `PROP_HBO_BLOCK_MAX`

Describes the number of blocks that may be offloaded from the NCP to the host. Default value is 32. Setting this value to zero will cause host block offload to be effectively disabled.

This value is encoded as an unsigned 16-bit integer.

This property is only available if the `CAP_HBO` capability is present in `PROP_CAPS`.

# 10. Feature: Jam Detection

Jamming detection is a feature that allows the NCP to report when it detects high levels of interference that are characteristic of intentional signal jamming.

The presence of this feature can be detected by checking for the presence of the `CAP_JAM_DETECT` (value 6) capability in `PROP_CAPS`.

# 10.1. Properties

# 10.1.1. PROP 4608: PROP_JAM_DETECT_ENABLE

- Type: Read-Write
- Packed-Encoding: `b`
- Default Value: false
- REQUIRED for `CAP_JAM_DETECT`

Octets: | 1
--- | ---
Fields: | `PROP_JAM_DETECT_ENABLE`

Indicates if jamming detection is enabled or disabled. Set to true to enable jamming detection.

This property is only available if the `CAP_JAM_DETECT` capability is present in `PROP_CAPS`.

# 10.1.2. PROP 4609: PROP_JAM_DETECTED

- Type: Read-Only
- Packed-Encoding: `b`
- REQUIRED for `CAP_JAM_DETECT`

Octets: | 1
--- | ---
Fields: | `PROP_JAM_DETECTED`

Set to true if radio jamming is detected. Set to false otherwise.

When jamming detection is enabled, changes to the value of this property are emitted asynchronously via `CMD_PROP_VALUE_IS`.

This property is only available if the `CAP_JAM_DETECT` capability is present in `PROP_CAPS`.

# 10.1.3. PROP 4610: PROP_JAM_DETECT_RSSI_THRESHOLD

- Type: Read-Write
- Packed-Encoding: `c`
- Units: dBm
- Default Value: Implementation-specific
- RECOMMENDED for `CAP_JAM_DETECT`

This parameter describes the threshold RSSI level (measured in dBm) above which the jamming detection will consider the channel blocked.

# 10.1.4. PROP 4611: PROP_JAM_DETECT_WINDOW

- Type: Read-Write
- Packed-Encoding: `c`
- Units: Seconds (1-64)
- Default Value: Implementation-specific
- RECOMMENDED for `CAP_JAM_DETECT`

This parameter describes the window period for signal jamming detection.

# 10.1.5. PROP 4612: PROP_JAM_DETECT_BUSY

- Type: Read-Write
- Packed-Encoding: `i`
- Units: Seconds (1-64)
- Default Value: Implementation-specific
- RECOMMENDED for `CAP_JAM_DETECT`

This parameter describes the number of aggregate seconds within the detection window where the RSSI must be above `PROP_JAM_DETECT_RSSI_THRESHOLD` to trigger detection.

The behavior of the jamming detection feature when `PROP_JAM_DETECT_BUSY` is larger than `PROP_JAM_DETECT_WINDOW` is undefined.

# 10.1.6. PROP 4613: SPINEL_PROP_JAM_DETECT_HISTORY_BITMAP

- Type: Read-Only
- Packed-Encoding: `LL`
- Default Value: Implementation-specific
- RECOMMENDED for `CAP_JAM_DETECT`

This value provides information about current state of jamming detection module for monitoring/debugging purpose. It returns a 64-bit value where each bit corresponds to one second interval starting with bit 0 for the most recent interval and bit 63 for the oldest intervals (63 sec earlier). The bit is set to 1 if the jamming detection module observed/detected high signal level during the corresponding one second interval. The value is read-only and is encoded as two `L` (uint32) values in little-endian format (first `L` (uint32) value gives the lower bits corresponding to more recent history).

# 11. Feature: GPIO Access

This feature allows the host to have control over some or all of the GPIO pins on the NCP. The host can determine which GPIOs are available by examining `PROP_GPIO_CONFIG`, described below. This API supports a maximum of 256 individual GPIO pins.

Support for this feature can be determined by the presence of `CAP_GPIO`.

# 11.1. Properties

# 11.1.1. PROP 4096: PROP_GPIO_CONFIG

- Argument-Encoding: `A(CCU)`
- Type: Read-write (Writable only using `CMD_PROP_VALUE_INSERT`, Section 4.5)

An array of structures which contain the following fields:

- `C`: GPIO Number
- `C`: GPIO Configuration Flags
- `U`: Human-readable GPIO name

GPIOs which do not have a corresponding entry are not supported.

The configuration parameter contains the configuration flags for the GPIO:

      0   1   2   3   4   5   6   7
    +---+---+---+---+---+---+---+---+
    |DIR|PUP|PDN|TRIGGER|  RESERVED |
    +---+---+---+---+---+---+---+---+
            |O/D|
            +---+

- `DIR`: Pin direction. Clear (0) for input, set (1) for output.
- `PUP`: Pull-up enabled flag.
- `PDN`/`O/D`: Flag meaning depends on pin direction:
  - Input: Pull-down enabled.
  - Output: Output is an open-drain.
- `TRIGGER`: Enumeration describing how pin changes generate asynchronous notification commands (TBD) from the NCP to the host.
  - 0: Feature disabled for this pin
  - 1: Trigger on falling edge
  - 2: Trigger on rising edge
  - 3: Trigger on level change
- `RESERVED`: Bits reserved for future use. Always cleared to zero and ignored when read.

As an optional feature, the configuration of individual pins may be modified using the `CMD_PROP_VALUE_INSERT` command. Only the GPIO number and flags fields MUST be present, the GPIO name (if present) would be ignored. This command can only be used to modify the configuration of GPIOs which are already exposed---it cannot be used by the host to add addional GPIOs.

# 11.1.2. PROP 4098: PROP_GPIO_STATE

- Type: Read-Write

Contains a bit field identifying the state of the GPIOs. The length of the data associated with these properties depends on the number of GPIOs. If you have 10 GPIOs, you'd have two bytes. GPIOs are numbered from most significant bit to least significant bit, so 0x80 is GPIO 0, 0x40 is GPIO 1, etc.

For GPIOs configured as inputs:

- `CMD_PROP_VAUE_GET`: The value of the associated bit describes the logic level read from the pin.
- `CMD_PROP_VALUE_SET`: The value of the associated bit is ignored for these pins.

For GPIOs configured as outputs:

- `CMD_PROP_VAUE_GET`: The value of the associated bit is implementation specific.
- `CMD_PROP_VALUE_SET`: The value of the associated bit determines the new logic level of the output. If this pin is configured as an open-drain, setting the associated bit to 1 will cause the pin to enter a Hi-Z state.

For GPIOs which are not specified in `PROP_GPIO_CONFIG`:

- `CMD_PROP_VAUE_GET`: The value of the associated bit is implementation specific.
- `CMD_PROP_VALUE_SET`: The value of the associated bit MUST be ignored by the NCP.

When writing, unspecified bits are assumed to be zero.

# 11.1.3. PROP 4099: PROP_GPIO_STATE_SET

- Type: Write-only

Allows for the state of various output GPIOs to be set without affecting other GPIO states. Contains a bit field identifying the output GPIOs that should have their state set to 1.

When writing, unspecified bits are assumed to be zero. The value of any bits for GPIOs which are not specified in `PROP_GPIO_CONFIG` MUST be ignored.

# 11.1.4. PROP 4100: PROP_GPIO_STATE_CLEAR

- Type: Write-only

Allows for the state of various output GPIOs to be cleared without affecting other GPIO states. Contains a bit field identifying the output GPIOs that should have their state cleared to 0.

When writing, unspecified bits are assumed to be zero. The value of any bits for GPIOs which are not specified in `PROP_GPIO_CONFIG` MUST be ignored.

# 12. Security Considerations

# 12.1. Raw Application Access

Spinel MAY be used as an API boundary for allowing processes to configure the NCP. However, such a system MUST NOT give unprivileged processess the ability to send or receive arbitrary command frames to the NCP. Only the specific commands and properties that are required should be allowed to be passed, and then only after being checked for proper format.

# Appendix A. Framing Protocol

Since this NCP protocol is defined independently of the physical transport or framing, any number of transports and framing protocols could be used successfully. However, in the interests of compatibility, this document provides some recommendations.

# A.1. UART Recommendations

The recommended default UART settings are:

- Bit rate: 115200
- Start bits: 1
- Data bits: 8
- Stop bits: 1
- Parity: None
- Flow Control: Hardware

These values may be adjusted depending on the individual needs of the application or product, but some sort of flow control MUST be used. Hardware flow control is preferred over software flow control. In the absence of hardware flow control, software flow control (XON/XOFF) MUST be used instead.

We also RECOMMEND an Arduino-style hardware reset, where the DTR signal is coupled to the `R̅E̅S̅` pin through a 0.01µF capacitor. This causes the NCP to automatically reset whenever the serial port is opened. At the very least we RECOMMEND dedicating one of your host pins to controlling the `R̅E̅S̅` pin on the NCP, so that you can easily perform a hardware reset if necessary.

# A.1.1. UART Bit Rate Detection

When using a UART, the issue of an appropriate bit rate must be considered. A bitrate of 115200 bits per second has become a defacto standard baud rate for many serial peripherals. This rate, however, is slower than the theoretical maximum bitrate of the 802.15.4 2.4GHz PHY (250kbit). In most circumstances this mismatch is not significant because the overall bitrate will be much lower than either of these rates, but there are circumstances where a faster UART bitrate is desirable. Thus, this document proposes a simple bitrate detection scheme that can be employed by the host to detect when the attached NCP is initially running at a higher bitrate.

The algorithm is to send successive NOOP commands to the NCP at increasing bitrates. When a valid `CMD_LAST_STATUS` response has been received, we have identified the correct bitrate.

In order to limit the time spent hunting for the appropriate bitrate, we RECOMMEND that only the following bitrates be checked:

- 115200
- 230400
- 1000000 (1Mbit)

The bitrate MAY also be changed programmatically by adjusting `PROP_UART_BITRATE`, if implemented.

# A.1.2. HDLC-Lite

HDLC-Lite is the recommended framing protocol for transmitting Spinel frames over a UART. HDLC-Lite consists of only the framing, escaping, and CRC parts of the larger HDLC protocol---all other parts of HDLC are omitted. This protocol was chosen because it works well with software flow control and is widely implemented.

To transmit a frame with HDLC-lite, the 16-bit CRC must first be appended to the frame. The CRC function is defined to be CRC-16/CCITT, otherwise known as the KERMIT CRC.

Individual frames are terminated with a frame delimiter octet called the 'flag' octet (`0x7E`).

The following octets values are considered special and should be escaped when present in data frames:

Octet Value | Description
--- | ---
0x7E | Frame Delimiter (Flag)
0x7D | Escape Byte
0x11 | XON
0x13 | XOFF
0xF8 | Vendor-Specific

When present in a data frame, these octet values are escaped by prepending the escape octet (`0x7D`) and XORing the value with `0x20`.

When receiving a frame, the CRC must be verified after the frame is unescaped. If the CRC value does not match what is calculated for the frame data, the frame MUST be discarded. The implementation MAY indicate the failure to higher levels to handle as they see fit, but MUST NOT attempt to process the deceived frame.

Consecutive flag octets are entirely legal and MUST NOT be treated as a framing error. Consecutive flag octets MAY be used as a way to wake up a sleeping NCP.

When first establishing a connection to the NCP, it is customary to send one or more flag octets to ensure that any previously received data is discarded.

# A.2. SPI Recommendations

We RECOMMEND the use of the following standard SPI signals:

- `C̅S̅`: (Host-to-NCP) Chip Select
- `CLK`: (Host-to-NCP) Clock
- `MOSI`: Master-Output/Slave-Input
- `MISO`: Master-Input/Slave-Output
- `I̅N̅T̅`: (NCP-to-Host) Host Interrupt
- `R̅E̅S̅`: (Host-to-NCP) NCP Hardware Reset

The `I̅N̅T̅` signal is used by the NCP to indicate to the host that the NCP has frames pending to send to it. When asserted, the host SHOULD initiate a SPI transaction in a timely manner.

We RECOMMEND the following SPI properties:

- `C̅S̅` is active low.
- `CLK` is active high.
- `CLK` speed is larger than 500 kHz.
- Data is valid on leading edge of `CLK`.
- Data is sent in multiples of 8-bits (octets).
- Octets are sent most-significant bit first.

This recommended configuration may be adjusted depending on the individual needs of the application or product.

# A.2.1. SPI Framing Protocol

Each SPI frame starts with a 5-byte frame header:

Octets: | 1 | 2 | 2
--- | --- | --- | ---
Fields: | HDR | RECV_LEN | DATA_LEN

- `HDR`: The first byte is the header byte (defined below)
- `RECV_LEN`: The second and third bytes indicate the largest frame size that that device is ready to receive. If zero, then the other device must not send any data. (Little endian)
- `DATA_LEN`: The fourth and fifth bytes indicate the size of the pending data frame to be sent to the other device. If this value is equal-to or less-than the number of bytes that the other device is willing to receive, then the data of the frame is immediately after the header. (Little Endian)

The `HDR` byte is defined as:

      0   1   2   3   4   5   6   7
    +---+---+---+---+---+---+---+---+
    |RST|CRC|CCF|  RESERVED |PATTERN|
    +---+---+---+---+---+---+---+---+

- `RST`: This bit is set when that device has been reset since the last time `C̅S̅` was asserted.
- `CRC`: This bit is set when that device supports writing a 16-bit CRC at the end of the data. The CRC length is NOT included in DATA_LEN.
- `CCF`: "CRC Check Failure". Set if the CRC check on the last received frame failed, cleared to zero otherwise. This bit is only used if both sides support CRC.
- `RESERVED`: These bits are all reserved for future used. They MUST be cleared to zero and MUST be ignored if set.
- `PATTERN`: These bits are set to a fixed value to help distinguish valid SPI frames from garbage (by explicitly making `0xFF` and `0x00` invalid values). Bit 6 MUST be set to be one and bit 7 MUST be cleared (0). A frame received that has any other values for these bits MUST be dropped.

Prior to a sending or receiving a frame, the master MAY send a 5-octet frame with zeros for both the max receive frame size and the the contained frame length. This will induce the slave device to indicate the length of the frame it wants to send (if any) and indicate the largest frame it is capable of receiving at the moment. This allows the master to calculate the size of the next transaction. Alternatively, if the master has a frame to send it can just go ahead and send a frame of that length and determine if the frame was accepted by checking that the `RECV_LEN` from the slave frame is larger than the frame the master just tried to send. If the `RECV_LEN` is smaller then the frame wasn't accepted and will need to be transmitted again.

This protocol can be used either unidirectionally or bidirectionally, determined by the behavior of the master and the slave.

If the the master notices `PATTERN` is not set correctly, the master should consider the transaction to have failed and try again after 10 milliseconds, retrying up to 200 times. After unsuccessfully trying 200 times in a row, the master MAY take appropriate remedial action (like a NCP hardware reset, or indicating a communication failure to a user interface).

At the end of the data of a frame is an optional 16-bit CRC, support for which is indicated by the `CRC` bit of the `HDR` byte being set. If these bits are set for both the master and slave frames, then CRC checking is enabled on both sides, effectively requiring that frame sizes be two bytes longer than would be otherwise required. The CRC is calculated using the same mechanism used for the CRC calculation in HDLC-Lite (See Appendix A.1.2). When both of the `CRC` bits are set, both sides must verify that the `CRC` is valid before accepting the frame. If not enough bytes were clocked out for the CRC to be read, then the frame must be ignored. If enough bytes were clocked out to perform a CRC check, but the CRC check fails, then the frame must be rejected and the `CRC_FAIL` bit on the next frame (and ONLY the next frame) MUST be set.

# A.3. I²C Recommendations

TBD

[CREF3]RQ: It may make sense to have a look at what Bluetooth HCI is doing for native I²C framing and go with that.

# A.4. Native USB Recommendations

TBD

[CREF4]RQ: It may make sense to have a look at what Bluetooth HCI is doing for native USB framing and go with that.

# Appendix B. Test Vectors

# B.1. Test Vector: Packed Unsigned Integer

Decimal Value | Packet Octet Encoding
--- | ---
0 | `00`
1 | `01`
127 | `7F`
128 | `80 01`
129 | `81 01`
1,337 | `B9 0A`
16,383 | `FF 7F`
16,384 | `80 80 01`
16,385 | `81 80 01`
2,097,151 | `FF FF 7F`

[CREF5]RQ: The PUI test-vector encodings need to be verified.

# B.2. Test Vector: Reset Command

- IID: 0
- TID: 0
- CMD: 1 (`CMD_RESET`)

Frame:

    80 01

# B.3. Test Vector: Reset Notification

- IID: 0
- TID: 0
- CMD: 6 (`CMD_VALUE_IS`)
- PROP: 0 (`PROP_LAST_STATUS`)
- VALUE: 114 (`STATUS_RESET_SOFTWARE`)

Frame:

    80 06 00 72

# B.4. Test Vector: Scan Beacon

- IID: 0
- TID: 0
- CMD: 7 (`CMD_VALUE_INSERTED`)
- PROP: 51 (`PROP_MAC_SCAN_BEACON`)
- VALUE: Structure, encoded as `CcT(ESSc.)T(iCUD.).`
  - CHAN: 15
  - RSSI: -60dBm
  - MAC_DATA: (0D 00 B6 40 D4 8C E9 38 F9 52 FF FF D2 04 00)
    - Long address: B6:40:D4:8C:E9:38:F9:52
    - Short address: 0xFFFF
    - PAN-ID: 0x04D2
    - LQI: 0
  - NET_DATA: (13 00 03 20 73 70 69 6E 65 6C 00 08 00 DE AD 00 BE EF 00 CA FE)
    - Protocol Number: 3
    - Flags: 0x20
    - Network Name: `spinel`
    - XPANID: `DE AD 00 BE EF 00 CA FE`

Frame:

    80 07 33 0F C4 0D 00 B6 40 D4 8C E9 38 F9 52 FF FF D2 04 00
    13 00 03 20 73 70 69 6E 65 6C 00 08 00 DE AD 00 BE EF 00 CA
    FE

# B.5. Test Vector: Inbound IPv6 Packet

CMD_VALUE_IS(PROP_STREAM_NET)

[CREF6]RQ: FIXME: This test vector is incomplete.

# B.6. Test Vector: Outbound IPv6 Packet

CMD_VALUE_SET(PROP_STREAM_NET)

[CREF7]RQ: FIXME: This test vector is incomplete.

# B.7. Test Vector: Fetch list of on-mesh networks

- IID: 0
- TID: 4
- CMD: 2 (`CMD_VALUE_GET`)
- PROP: 90 (`PROP_THREAD_ON_MESH_NETS`)

Frame:

    84 02 5A

# B.8. Test Vector: Returned list of on-mesh networks

- IID: 0
- TID: 4
- CMD: 6 (`CMD_VALUE_IS`)
- PROP: 90 (`PROP_THREAD_ON_MESH_NETS`)
- VALUE: Array of structures, encoded as `A(T(6CbC))`

IPv6 Prefix | Prefix Length | Stable Flag | Other Flags
--- | --- | --- | ---
2001:DB8:1:: | 64 | True | ??
2001:DB8:2:: | 64 | False | ??

Frame:

    84 06 5A 13 00 20 01 0D B8 00 01 00 00 00 00 00 00 00 00 00
    00 40 01 ?? 13 00 20 01 0D B8 00 02 00 00 00 00 00 00 00 00
    00 00 40 00 ??

# B.9. Test Vector: Adding an on-mesh network

- IID: 0
- TID: 5
- CMD: 4 (`CMD_VALUE_INSERT`)
- PROP: 90 (`PROP_THREAD_ON_MESH_NETS`)
- VALUE: Structure, encoded as `6CbCb`

IPv6 Prefix | Prefix Length | Stable Flag | Other Flags
--- | --- | --- | ---
2001:DB8:3:: | 64 | True | ??

Frame:

    85 03 5A 20 01 0D B8 00 03 00 00 00 00 00 00 00 00 00 00 40
    01 ?? 01

[CREF8]RQ: FIXME: This test vector is incomplete.

# B.10. Test Vector: Insertion notification of an on-mesh network

- IID: 0
- TID: 5
- CMD: 7 (`CMD_VALUE_INSERTED`)
- PROP: 90 (`PROP_THREAD_ON_MESH_NETS`)
- VALUE: Structure, encoded as `6CbCb`

IPv6 Prefix | Prefix Length | Stable Flag | Other Flags
--- | --- | --- | ---
2001:DB8:3:: | 64 | True | ??

Frame:

    85 07 5A 20 01 0D B8 00 03 00 00 00 00 00 00 00 00 00 00 40
    01 ?? 01

[CREF9]RQ: FIXME: This test vector is incomplete.

# B.11. Test Vector: Removing a local on-mesh network

- IID: 0
- TID: 6
- CMD: 5 (`CMD_VALUE_REMOVE`)
- PROP: 90 (`PROP_THREAD_ON_MESH_NETS`)
- VALUE: IPv6 Prefix `2001:DB8:3::`

Frame:

    86 05 5A 20 01 0D B8 00 03 00 00 00 00 00 00 00 00 00 00

# B.12. Test Vector: Removal notification of an on-mesh network

- IID: 0
- TID: 6
- CMD: 8 (`CMD_VALUE_REMOVED`)
- PROP: 90 (`PROP_THREAD_ON_MESH_NETS`)
- VALUE: IPv6 Prefix `2001:DB8:3::`

Frame:

    86 08 5A 20 01 0D B8 00 03 00 00 00 00 00 00 00 00 00 00

# Appendix C. Example Sessions

# C.1. NCP Initialization

[CREF10]RQ: FIXME: This example session is incomplete.

Check the protocol version to see if it is supported:

- CMD_VALUE_GET:PROP_PROTOCOL_VERSION
- CMD_VALUE_IS:PROP_PROTOCOL_VERSION

Check the NCP version to see if a firmware update may be necessary:

- CMD_VALUE_GET:PROP_NCP_VERSION
- CMD_VALUE_IS:PROP_NCP_VERSION

Check interface type to make sure that it is what we expect:

- CMD_VALUE_GET:PROP_INTERFACE_TYPE
- CMD_VALUE_IS:PROP_INTERFACE_TYPE

If the host supports using vendor-specific commands, the vendor should be verified before using them:

- CMD_VALUE_GET:PROP_VENDOR_ID
- CMD_VALUE_IS:PROP_VENDOR_ID

Fetch the capability list so that we know what features this NCP supports:

- CMD_VALUE_GET:PROP_CAPS
- CMD_VALUE_IS:PROP_CAPS

If the NCP supports CAP_NET_SAVE, then we go ahead and recall the network:

- CMD_NET_RECALL

# C.2. Attaching to a network

[CREF11]RQ: FIXME: This example session is incomplete.

We make the assumption that the NCP is not currently associated with a network.

Set the network properties, if they were not already set:

- CMD_VALUE_SET:PROP_PHY_CHAN
- CMD_VALUE_IS:PROP_PHY_CHAN
- CMD_VALUE_SET:PROP_NET_XPANID
- CMD_VALUE_IS:PROP_NET_XPANID
- CMD_VALUE_SET:PROP_MAC_15_4_PANID
- CMD_VALUE_IS:PROP_MAC_15_4_PANID
- CMD_VALUE_SET:PROP_NET_NETWORK_NAME
- CMD_VALUE_IS:PROP_NET_NETWORK_NAME
- CMD_VALUE_SET:PROP_NET_MASTER_KEY
- CMD_VALUE_IS:PROP_NET_MASTER_KEY
- CMD_VALUE_SET:PROP_NET_KEY_SEQUENCE_COUNTER
- CMD_VALUE_IS:PROP_NET_KEY_SEQUENCE_COUNTER
- CMD_VALUE_SET:PROP_NET_KEY_SWITCH_GUARDTIME
- CMD_VALUE_IS:PROP_NET_KEY_SWITCH_GUARDTIME

Bring the network interface up:

- CMD_VALUE_SET:PROP_NET_IF_UP:TRUE
- CMD_VALUE_IS:PROP_NET_IF_UP:TRUE

Bring the routing stack up:

- CMD_VALUE_SET:PROP_NET_STACK_UP:TRUE
- CMD_VALUE_IS:PROP_NET_STACK_UP:TRUE

Some asynchronous events from the NCP:

- CMD_VALUE_IS:PROP_NET_ROLE
- CMD_VALUE_IS:PROP_NET_PARTITION_ID
- CMD_VALUE_IS:PROP_THREAD_ON_MESH_NETS

# C.3. Successfully joining a pre-existing network

[CREF12]RQ: FIXME: This example session is incomplete.

This example session is identical to the above session up to the point where we set PROP_NET_IF_UP to true. From there, the behavior changes.

- CMD_VALUE_SET:PROP_NET_REQUIRE_JOIN_EXISTING:TRUE
- CMD_VALUE_IS:PROP_NET_REQUIRE_JOIN_EXISTING:TRUE

Bring the routing stack up:

- CMD_VALUE_SET:PROP_NET_STACK_UP:TRUE
- CMD_VALUE_IS:PROP_NET_STACK_UP:TRUE

Some asynchronous events from the NCP:

- CMD_VALUE_IS:PROP_NET_ROLE
- CMD_VALUE_IS:PROP_NET_PARTITION_ID
- CMD_VALUE_IS:PROP_THREAD_ON_MESH_NETS

Now let's save the network settings to NVRAM:

- CMD_NET_SAVE

# C.4. Unsuccessfully joining a pre-existing network

This example session is identical to the above session up to the point where we set PROP_NET_IF_UP to true. From there, the behavior changes.

- CMD_VALUE_SET:PROP_NET_REQUIRE_JOIN_EXISTING:TRUE
- CMD_VALUE_IS:PROP_NET_REQUIRE_JOIN_EXISTING:TRUE

Bring the routing stack up:

- CMD_VALUE_SET:PROP_NET_STACK_UP:TRUE
- CMD_VALUE_IS:PROP_NET_STACK_UP:TRUE

Some asynchronous events from the NCP:

- CMD_VALUE_IS:PROP_LAST_STATUS:STATUS_JOIN_NO_PEERS
- CMD_VALUE_IS:PROP_NET_STACK_UP:FALSE

# C.5. Detaching from a network

TBD

# C.6. Attaching to a saved network

[CREF13]RQ: FIXME: This example session is incomplete.

Recall the saved network if you haven't already done so:

- CMD_NET_RECALL

Bring the network interface up:

- CMD_VALUE_SET:PROP_NET_IF_UP:TRUE
- CMD_VALUE_IS:PROP_NET_IF_UP:TRUE

Bring the routing stack up:

- CMD_VALUE_SET:PROP_NET_STACK_UP:TRUE
- CMD_VALUE_IS:PROP_NET_STACK_UP:TRUE

Some asynchronous events from the NCP:

- CMD_VALUE_IS:PROP_NET_ROLE
- CMD_VALUE_IS:PROP_NET_PARTITION_ID
- CMD_VALUE_IS:PROP_THREAD_ON_MESH_NETS

# C.7. NCP Software Reset

[CREF14]RQ: FIXME: This example session is incomplete.

- CMD_RESET
- CMD_VALUE_IS:PROP_LAST_STATUS:STATUS_RESET_SOFTWARE

Then jump to Appendix C.1.

# C.8. Adding an on-mesh prefix

TBD

# C.9. Entering low-power modes

TBD

# C.10. Sniffing raw packets

[CREF15]RQ: FIXME: This example session is incomplete.

This assumes that the NCP has been initialized.

Optionally set the channel:

- CMD_VALUE_SET:PROP_PHY_CHAN:x
- CMD_VALUE_IS:PROP_PHY_CHAN

Set the filter mode:

- CMD_VALUE_SET:PROP_MAC_PROMISCUOUS_MODE:MAC_PROMISCUOUS_MODE_MONITOR
- CMD_VALUE_IS:PROP_MAC_PROMISCUOUS_MODE:MAC_PROMISCUOUS_MODE_MONITOR

Enable the raw stream:

- CMD_VALUE_SET:PROP_MAC_RAW_STREAM_ENABLED:TRUE
- CMD_VALUE_IS:PROP_MAC_RAW_STREAM_ENABLED:TRUE

Enable the PHY directly:

- CMD_VALUE_SET:PROP_PHY_ENABLED:TRUE
- CMD_VALUE_IS:PROP_PHY_ENABLED:TRUE

Now we will get raw 802.15.4 packets asynchronously on PROP_STREAM_RAW:

- CMD_VALUE_IS:PROP_STREAM_RAW:...
- CMD_VALUE_IS:PROP_STREAM_RAW:...
- CMD_VALUE_IS:PROP_STREAM_RAW:...

This mode may be entered even when associated with a network. In that case, you should set `PROP_MAC_PROMISCUOUS_MODE` to `MAC_PROMISCUOUS_MODE_PROMISCUOUS` or `MAC_PROMISCUOUS_MODE_NORMAL`, so that you can avoid receiving packets from other networks or that are destined for other nodes.

# Appendix D. Acknowledgments

Special thanks to Abtin Keshavarzian, Martin Turon, Arjuna Sivasithambaresan and Jonathan Hui for their substantial contributions and feedback related to this document.

[CREF16]RQ: If I have missed anyone who has contributed to this document, please let me know ASAP.

This document was prepared using mmark by (Miek Gieben) and xml2rfc (version 2).

# Appendix E. Glossary

[CREF17]RQ: Alphabetize before finalization.

NCP
  Acronym for Network Control Processor.
Host
  Computer or Micro-controller which controls the NCP.
TID
  Transaction Identifier. May be a value between zero and fifteen. See Section 2.1.3 for more information.
IID
  Interface Identifier. May be a value between zero and three. See Section 2.1.2 for more information.
PUI
  Packed Unsigned Integer. A way to serialize an unsigned integer using one, two, or three bytes. Used throughout the Spinel protocol. See Section 3.2 for more information.
FCS
  Final Checksum. Bytes added to the end of a packet to help determine if the packet was received without corruption.
PHY
  Physical layer. Refers to characteristics and parameters related to the physical implementation and operation of a networking medium.

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