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CC2538: Better handling of UART receive code (#995)

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* Better handling of UART receive code

* Update logic to use head and tail
This commit is contained in:
Nick Banks
2016-11-22 08:42:51 -08:00
committed by Jonathan Hui
parent e40947eb6f
commit 484172cc14
1 changed files with 32 additions and 24 deletions
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examples/platforms/cc2538/uart.c
+32 -24
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@@ -54,14 +54,25 @@ static void processTransmit(void);
static const uint8_t *sTransmitBuffer = NULL;
static uint16_t sTransmitLength = 0;
static uint8_t sReceiveBuffer[kReceiveBufferSize];
static uint16_t sReceiveHead = 0;
static uint16_t sReceiveLength = 0;
typedef struct RecvBuffer
{
// The data buffer
uint8_t mBuffer[kReceiveBufferSize];
// The offset of the first item written to the list.
uint16_t mHead;
// The offset of the next item to be written to the list.
uint16_t mTail;
} RecvBuffer;
static RecvBuffer sReceive;
ThreadError otPlatUartEnable(void)
{
uint32_t div;
sReceive.mHead = 0;
sReceive.mTail = 0;
// clock
HWREG(SYS_CTRL_RCGCUART) = SYS_CTRL_RCGCUART_UART0;
HWREG(SYS_CTRL_SCGCUART) = SYS_CTRL_SCGCUART_UART0;
@@ -119,28 +130,26 @@ exit:
void processReceive(void)
{
uint16_t remaining;
// Copy tail to prevent multiple reads
uint16_t tail = sReceive.mTail;
VerifyOrExit(sReceiveLength > 0, ;);
remaining = kReceiveBufferSize - sReceiveHead;
if (sReceiveLength >= remaining)
// If the data wraps around, process the first part
if (sReceive.mHead > tail)
{
otPlatUartReceived(sReceiveBuffer + sReceiveHead, remaining);
sReceiveHead = 0;
sReceiveLength -= remaining;
otPlatUartReceived(sReceive.mBuffer + sReceive.mHead, kReceiveBufferSize - sReceive.mHead);
// Reset the buffer mHead back to zero.
sReceive.mHead = 0;
}
if (sReceiveLength > 0)
// For any data remaining, process it
if (sReceive.mHead != tail)
{
otPlatUartReceived(sReceiveBuffer + sReceiveHead, sReceiveLength);
sReceiveHead += sReceiveLength;
sReceiveLength = 0;
}
otPlatUartReceived(sReceive.mBuffer + sReceive.mHead, tail - sReceive.mHead);
exit:
return;
// Set mHead to the local tail we have cached
sReceive.mHead = tail;
}
}
void processTransmit(void)
@@ -170,7 +179,6 @@ void cc2538UartProcess(void)
void UART0IntHandler(void)
{
uint32_t mis;
uint16_t tail;
uint8_t byte;
mis = HWREG(UART0_BASE + UART_O_MIS);
@@ -182,11 +190,11 @@ void UART0IntHandler(void)
{
byte = HWREG(UART0_BASE + UART_O_DR);
if (sReceiveLength < kReceiveBufferSize)
// We can only write if incrementing mTail doesn't equal mHead
if (sReceive.mHead != (sReceive.mTail + 1) % kReceiveBufferSize)
{
tail = (sReceiveHead + sReceiveLength) % kReceiveBufferSize;
sReceiveBuffer[tail] = byte;
sReceiveLength++;
sReceive.mBuffer[sReceive.mTail] = byte;
sReceive.mTail = (sReceive.mTail + 1) % kReceiveBufferSize;
}
}
}