[cc2538] add energy scan (#5681)

This commit provides a simple energy scan implementation on CC2538
platform.

examples/platforms/cc2538/alarm.c

@@ -52,6 +52,17 @@ static uint32_t sAlarmT0   = 0;
 static uint32_t sAlarmDt   = 0;
 static bool     sIsRunning = false;
 
+static uint8_t  sTimersIsRunning = 0;
+static uint32_t sTimersExpireAt[OT_CC2538_TIMERS_COUNT];
+
+extern void cc2538EnergyScanTimerHandler(void);
+
+void cc2538SetTimer(otCC2538Timer aTimer, uint32_t aDelay)
+{
+    sTimersIsRunning |= (1 << aTimer);
+    sTimersExpireAt[aTimer] = sCounter + aDelay;
+}
+
 void cc2538AlarmInit(void)
 {
     HWREG(NVIC_ST_RELOAD) = kSystemClock / kTicksPerSec;
@@ -84,6 +95,15 @@ void cc2538AlarmProcess(otInstance *aInstance)
     uint32_t expires;
     bool     fire = false;
 
+    if (sTimersIsRunning)
+    {
+        if ((int32_t)(sTimersExpireAt[OT_CC2538_TIMER_ENERGY_SCAN] - sCounter) < 0)
+        {
+            sTimersIsRunning &= ~(1 << OT_CC2538_TIMER_ENERGY_SCAN);
+            cc2538EnergyScanTimerHandler();
+        }
+    }
+
     if (sIsRunning)
     {
         expires = sAlarmT0 + sAlarmDt;

examples/platforms/cc2538/cc2538-reg.h

@@ -95,6 +95,7 @@
 #define RFCORE_XREG_FSMSTAT1                    0x4008864C  // Radio status register
 #define RFCORE_XREG_FIFOPCTRL                   0x40088650  // FIFOP threshold
 #define RFCORE_XREG_CCACTRL0                    0x40088658  // CCA threshold
+#define RFCORE_XREG_RSSI                        0x40088660  // RSSI status register
 #define RFCORE_XREG_RSSISTAT                    0x40088664  // RSSI valid status register
 #define RFCORE_XREG_AGCCTRL1                    0x400886C8  // AGC reference level
 #define RFCORE_XREG_RFC_OBS_CTRL                0x400887AC  // RF Core observable output
@@ -109,6 +110,7 @@
 #define RFCORE_XREG_FRMFILT0_FRAME_FILTER_EN    0x00000001  // Enables frame filtering
 
 #define RFCORE_XREG_FRMCTRL0_AUTOACK            0x00000020
+#define RFCORE_XREG_FRMCTRL0_ENERGY_SCAN        0x00000010
 #define RFCORE_XREG_FRMCTRL0_AUTOCRC            0x00000040
 #define RFCORE_XREG_FRMCTRL0_INFINITY_RX        0x00000008
 

examples/platforms/cc2538/platform-cc2538.h

@@ -104,4 +104,19 @@ void cc2538RadioSetHgm(bool aState);
 bool cc2538RadioGetHgm(void);
 #endif // OPENTHREAD_CONFIG_CC2538_WITH_CC2592 && OPENTHREAD_CONFIG_CC2592_USE_HGM
 
+typedef enum
+{
+    OT_CC2538_TIMER_ENERGY_SCAN, ///< Internal timer for energy scan
+    OT_CC2538_TIMERS_COUNT,      ///< Number of internal timers
+} otCC2538Timer;
+
+/**
+ * This function sets the internal timer.
+ *
+ * @param[in]   aTimer  The timer identifier.
+ * @param[in]   aDelay  The delay to trigger the timer, and must be no more than `INT32_MAX`.
+ *
+ */
+void cc2538SetTimer(otCC2538Timer aTimer, uint32_t aDelay);
+
 #endif // PLATFORM_CC2538_H_

examples/platforms/cc2538/radio.c

@@ -178,6 +178,8 @@ static bool         sIsReceiverEnabled = false;
 static uint8_t sDroppedFrameLength = 0;
 #endif
 
+static int8_t cc2538RadioGetRssiOffset(void);
+
 void enableReceiver(void)
 {
     if (!sIsReceiverEnabled)
@@ -622,14 +624,30 @@ int8_t otPlatRadioGetRssi(otInstance *aInstance)
 {
     OT_UNUSED_VARIABLE(aInstance);
 
-    return 0;
+    int8_t rssi = OT_RADIO_RSSI_INVALID;
+
+    if ((HWREG(RFCORE_XREG_RSSISTAT) & RFCORE_XREG_RSSISTAT_RSSI_VALID) != 0)
+    {
+        rssi = HWREG(RFCORE_XREG_RSSI) & 0xff;
+
+        if (rssi <= cc2538RadioGetRssiOffset() - 128)
+        {
+            rssi -= cc2538RadioGetRssiOffset();
+        }
+        else
+        {
+            rssi = -128;
+        }
+    }
+
+    return rssi;
 }
 
 otRadioCaps otPlatRadioGetCaps(otInstance *aInstance)
 {
     OT_UNUSED_VARIABLE(aInstance);
 
-    return OT_RADIO_CAPS_NONE;
+    return OT_RADIO_CAPS_ENERGY_SCAN;
 }
 
 static bool cc2538RadioGetPromiscuous(void)
@@ -1017,6 +1035,23 @@ int8_t findSrcMatchAvailEntry(bool aShort)
     return entry;
 }
 
+void cc2538EnergyScanTimerHandler(void)
+{
+    int8_t rssi = otPlatRadioGetRssi(sInstance);
+
+    disableReceiver();
+
+    HWREG(RFCORE_XREG_FRMCTRL0) &= ~RFCORE_XREG_FRMCTRL0_ENERGY_SCAN;
+    HWREG(RFCORE_XREG_FREQCTRL) = 11 + (sChannel - 11) * 5;
+
+    if (sIsReceiverEnabled)
+    {
+        enableReceiver();
+    }
+
+    otPlatRadioEnergyScanDone(sInstance, rssi);
+}
+
 void otPlatRadioEnableSrcMatch(otInstance *aInstance, bool aEnable)
 {
     OT_UNUSED_VARIABLE(aInstance);
@@ -1155,10 +1190,31 @@ void otPlatRadioClearSrcMatchExtEntries(otInstance *aInstance)
 otError otPlatRadioEnergyScan(otInstance *aInstance, uint8_t aScanChannel, uint16_t aScanDuration)
 {
     OT_UNUSED_VARIABLE(aInstance);
-    OT_UNUSED_VARIABLE(aScanChannel);
-    OT_UNUSED_VARIABLE(aScanDuration);
 
-    return OT_ERROR_NOT_IMPLEMENTED;
+    otLogInfoPlat("ScanChannel=%d", aScanChannel);
+
+    if (aScanChannel != sChannel)
+    {
+        if (sIsReceiverEnabled)
+        {
+            disableReceiver();
+        }
+
+        HWREG(RFCORE_XREG_FREQCTRL) = 11 + (aScanChannel - 11) * 5;
+
+        enableReceiver();
+    }
+    else if (!sIsReceiverEnabled)
+    {
+        enableReceiver();
+    }
+
+    // Collect peak signal strength
+    HWREG(RFCORE_XREG_FRMCTRL0) |= RFCORE_XREG_FRMCTRL0_ENERGY_SCAN;
+
+    cc2538SetTimer(OT_CC2538_TIMER_ENERGY_SCAN, aScanDuration);
+
+    return OT_ERROR_NONE;
 }
 
 otError otPlatRadioGetTransmitPower(otInstance *aInstance, int8_t *aPower)