esp32: Fix hang in AS923 due to incorrect timer behaviour.

Author: Daniel Campora

drivers/sx127x/sx1276/sx1276.c

@@ -268,16 +268,14 @@ bool SX1276IsChannelFree( RadioModems_t modem, uint32_t freq, int16_t rssiThresh
     carrierSenseTime = TimerGetCurrentTime( );
 
     // Perform carrier sense for maxCarrierSenseTime
-    while( TimerGetElapsedTime( carrierSenseTime ) < maxCarrierSenseTime )
-    {
+    do {
         rssi = SX1276ReadRssi( modem );
 
-        if( rssi > rssiThresh )
-        {
+        if ( rssi > rssiThresh ) {
             status = false;
             break;
         }
-    }
+    } while( TimerGetElapsedTime( carrierSenseTime ) < maxCarrierSenseTime );
     SX1276SetSleep( );
     return status;
 }

esp32/lora/timer-board.c

@@ -57,18 +57,11 @@ static TimerTime_t TimerTickCounterContext = 0;
  */
 volatile TimerTime_t TimeoutCntValue = 0;
 
-/*!
- * Timer enabled/disabled flag
- */
-volatile bool TimerEnabled = false;
-
 
 static IRAM_ATTR void TimerCallback (void) {
-    if (TimerEnabled) {
-        TimerTickCounter++;
-        if (TimerTickCounter == TimeoutCntValue) {
-            TimerIrqHandler();
-        }
+    TimerTickCounter++;
+    if (TimeoutCntValue > 0 && TimerTickCounter == TimeoutCntValue) {
+        TimerIrqHandler();
     }
 }
 
@@ -96,12 +89,11 @@ IRAM_ATTR void TimerHwStart (uint32_t val) {
     } else {
         TimeoutCntValue = TimerTickCounterContext + val;
     }
-    TimerEnabled = true;
     MICROPY_END_ATOMIC_SECTION(ilevel);
 }
 
 void IRAM_ATTR TimerHwStop( void ) {
-    TimerEnabled = false;
+
 }
 
 void TimerHwDelayMs( uint32_t delay ) {
@@ -126,10 +118,6 @@ IRAM_ATTR TimerTime_t TimerHwGetElapsedTime (void) {
 IRAM_ATTR TimerTime_t TimerHwComputeTimeDifference( TimerTime_t eventInTime ) {
     TimerTime_t currTime = TimerHwGetTime();
 
-    if (eventInTime == 0) {
-        return 0;
-    }
-
     if (eventInTime <= currTime) {
         return currTime - eventInTime;
     } else {
@@ -139,4 +127,5 @@ IRAM_ATTR TimerTime_t TimerHwComputeTimeDifference( TimerTime_t eventInTime ) {
 }
 
 void TimerHwEnterLowPowerStopMode( void ) {
+
 }