Merge pull request #941 from ABOSTM/HARDWARETIMER_ANALOGWRITE_NO_GLITCH

Hardwaretimer analogWrite() no glitch

Author: fpistm

cores/arduino/HardwareTimer.cpp

@@ -690,6 +690,20 @@ void HardwareTimer::setMode(uint32_t channel, TimerModes_t mode, PinName pin)
   }
 }
 
+/**
+  * @brief  Retrieves channel mode configured
+  * @param  channel: Arduino channel [1..4]
+  * @retval returns configured mode
+  */
+TimerModes_t HardwareTimer::getMode(uint32_t channel)
+{
+  if ((1 <= channel) && (channel <= TIMER_CHANNELS)) {
+    return _ChannelMode[channel - 1];
+  } else {
+    return TIMER_DISABLED;
+  }
+}
+
 /**
   * @brief  Enable or disable preloading for overflow value
   *         When disabled, changes to the overflow value take effect

cores/arduino/HardwareTimer.h

@@ -118,6 +118,8 @@ class HardwareTimer {
     void setMode(uint32_t channel, TimerModes_t mode, PinName pin = NC); // Configure timer channel with specified mode on specified pin if available
     void setMode(uint32_t channel, TimerModes_t mode, uint32_t pin);
 
+    TimerModes_t getMode(uint32_t channel);  // Retrieve configured mode
+
     void setPreloadEnable(bool value); // Configure overflow preload enable setting
 
     uint32_t getCaptureCompare(uint32_t channel, TimerCompareFormat_t format = TICK_COMPARE_FORMAT); // return Capture/Compare register value of specified channel depending on format provided

libraries/SrcWrapper/src/stm32/analog.cpp

@@ -1028,6 +1028,7 @@ void pwm_start(PinName pin, uint32_t PWM_freq, uint32_t value, TimerCompareForma
 {
   TIM_TypeDef *Instance = (TIM_TypeDef *)pinmap_peripheral(pin, PinMap_PWM);
   HardwareTimer *HT;
+  TimerModes_t previousMode;
   uint32_t index = get_timer_index(Instance);
   if (HardwareTimer_Handle[index] == NULL) {
     HardwareTimer_Handle[index]->__this = new HardwareTimer((TIM_TypeDef *)pinmap_peripheral(pin, PinMap_PWM));
@@ -1037,10 +1038,15 @@ void pwm_start(PinName pin, uint32_t PWM_freq, uint32_t value, TimerCompareForma
 
   uint32_t channel = STM_PIN_CHANNEL(pinmap_function(pin, PinMap_PWM));
 
-  HT->setMode(channel, TIMER_OUTPUT_COMPARE_PWM1, pin);
+  previousMode = HT->getMode(channel);
+  if (previousMode != TIMER_OUTPUT_COMPARE_PWM1) {
+    HT->setMode(channel, TIMER_OUTPUT_COMPARE_PWM1, pin);
+  }
   HT->setOverflow(PWM_freq, HERTZ_FORMAT);
   HT->setCaptureCompare(channel, value, resolution);
-  HT->resume();
+  if (previousMode != TIMER_OUTPUT_COMPARE_PWM1) {
+    HT->resume();
+  }
 }
 /**
   * @brief  This function will disable the PWM