Is there any way to prevent the PWM from outputting during initialization?

[ShiPC123]

Hello everyone. I used a hardware timer to generate PWM. During the initialization of PWM, the PWM starts to output by default. Is there any way to solve this problem?

this is my code

void Compare_IT_callback(void) {  // Compare match event correspond to falling edge of PWM when configured in PWM1 mode

  if (++pulseCounter >= PULSE_NUM) {
    MyTim->pause();
    digitalWrite(TRIAC_PIN, LOW);
  }
}





void setup() {
  Serial1.begin(115200);
  pinMode(RELAY_PIN, OUTPUT);

  TIM_TypeDef *Instance = (TIM_TypeDef *)pinmap_peripheral(digitalPinToPinName(TRIAC_PIN), PinMap_PWM);
  uint32_t channel = STM_PIN_CHANNEL(pinmap_function(digitalPinToPinName(TRIAC_PIN), PinMap_PWM));


  MyTim = new HardwareTimer(Instance);

  // MyTim->setMode(channel, TIMER_OUTPUT_COMPARE_PWM1, TRIAC_PIN);
  // // MyTim->setPrescaleFactor(8); // Due to setOverflow with MICROSEC_FORMAT, prescaler will be computed automatically based on timer input clock
  // MyTim->setOverflow(PWM_PERIOD_US, MICROSEC_FORMAT);  //
  // MyTim->setCaptureCompare(channel, PWM_DUTY_US, PERCENT_COMPARE_FORMAT);
  // MyTim->attachInterrupt(channel, Compare_IT_callback);
  // MyTim->pause();
  // digitalWrite(TRIAC_PIN, LOW);
    MyTim->pause();
  MyTim->setPWM(channel, TRIAC_PIN, TRIAC_PIN, 20, NULL, Compare_IT_callback);

}

As long as you call MyTim->setPWM(channel, TRIAC_PIN, TRIAC_PIN, 20, NULL, Compare_IT_callback); the PWM output will be directly enabled.

[ShiPC123]

If the code is written like this, the PWM pin will remain at a continuous high level, and using the digitalWrite function will also be ineffective.

[fpistm]

Hi @ShiPC123
this is normal, when the GPIO is configured for the Timer, the AF is set and so digitalWrite has no effect.

Aabout the setPWM, it is also normal as you ask to configure and run the PWM on the specified GPIO. This is the goal of setPWM which is a full in one API to configure and run.
If you want only configure you have to do it step by step and don't call resume while you don't want output the pwm:

  MyTim->setMode(channel, TIMER_OUTPUT_COMPARE_PWM1, pin);
  // MyTim->setPrescaleFactor(8); // Due to setOverflow with MICROSEC_FORMAT, prescaler will be computed automatically based on timer input clock
  MyTim->setOverflow(100000, MICROSEC_FORMAT); // 100000 microseconds = 100 milliseconds
  MyTim->setCaptureCompare(channel, 50, PERCENT_COMPARE_FORMAT); // 50%
  MyTim->attachInterrupt(Update_IT_callback);
  MyTim->attachInterrupt(channel, Compare_IT_callback);
  MyTim->resume();

[ShiPC123]

I tested this code. I didn't call the resume() function, but the PWM pin output a high level upon power-on. I want the PWM pin to output a low level when it is not called.

[fpistm]

Guess it is the default state when configured.

[fpistm]

Maybe link to the default pull defined in the PeripheralPins.c.
Example for STM32F411RE:
https://github.com/stm32duino/Arduino_Core_STM32/blob/e881e8cbe25cccff906e87501e8c3fd441f8edd3/variants/STM32F4xx/F411R(C-E)T/PeripheralPins.c#L87-L92

You can override the const PinMap PinMap_TIM[] array as it is defined as WEAK.

const PinMap PinMap_TIM[] = {
  {PA_0,      TIM2,  STM_PIN_DATA_EXT(STM_MODE_AF_PP, GPIO_PULLDOWN, GPIO_AF1_TIM2, 1, 0)}, // TIM2_CH1
  {PA_0_ALT1, TIM5,  STM_PIN_DATA_EXT(STM_MODE_AF_PP, GPIO_PULLDOWN, GPIO_AF2_TIM5, 1, 0)}, // TIM5_CH1
  {PA_1,      TIM2,  STM_PIN_DATA_EXT(STM_MODE_AF_PP, GPIO_PULLDOWN, GPIO_AF1_TIM2, 2, 0)}, // TIM2_CH2
  {PA_1_ALT1, TIM5,  STM_PIN_DATA_EXT(STM_MODE_AF_PP, GPIO_PULLDOWN, GPIO_AF2_TIM5, 2, 0)}, // TIM5_CH2
  {PA_2,      TIM2,  STM_PIN_DATA_EXT(STM_MODE_AF_PP, GPIO_PULLDOWN, GPIO_AF1_TIM2, 3, 0)}, // TIM2_CH3
...
};

Of course, use the one for the mcu you used.

[ShiPC123]

Thank you. The problem has been solved.