How to configure GPDMA for PWM generation?

[m4rk0401]

Hi,

I'm using a Riverdi RVT50HQSFWN00 Screen with the STM32U5A9NJH6Q MCU. COnnected to pin PI0 is a WS2812 LED light strip. I already configured the timer 5 channel 4 for PWM generation and validated it with a scope at the pin. Right now I'm stuck at the GPDMA part. I'm able to start the PWM generation using: HAL_TIM_PWM_Start_DMA(&htim8, TIM_CHANNEL_1, (uint32_t *)pwmData, indx);

For the code I followed this tutorial: https://controllerstech.com/interface-ws2812-with-stm32/

This is my timer configuration (TIM5 global interrupt enabled):

This is GPDMA configuration:

Using a scope, I see that a PWM signal is generated but the HAL_TIM_PWM_PulseFinishedCallback() function is never called, which in the end, stops the DMA transfer.

Would really appreciate any help.

Best regards
Marko

[Sarra.S]

Hello @m4rk0401, 

In your GPDMA configuration, in the destination data setting, try enabling the destination address increment after transfer

[m4rk0401]

Thanks @Sarra.S for your quick response. I tried your suggestion without success.

I tried some more debugging today and achieved following result:

Code (reduced to most important parts) - app_freertos.c: 

int datasentflag = 0;
extern TIM_HandleTypeDef htim5;

void HAL_TIM_PWM_PulseFinishedCallback(TIM_HandleTypeDef *htim)
{
	HAL_TIM_PWM_Stop_DMA(&htim5, TIM_CHANNEL_4);
	datasentflag=1;
}

uint16_t pwmData[24];
void test()
{
	for(int i=0; i<24; i++)
	{
		pwmData[i] = 50;
	}

	HAL_TIM_PWM_Start_DMA(&htim5, TIM_CHANNEL_4, (uint32_t *)pwmData, 24);
	/*
	while (!datasentflag){};
	datasentflag = 0;
	*/
}

void StartDefaultTask(void *argument)
{
  /* USER CODE BEGIN defaultTask */
  /* Infinite loop */
  for(;;)
  {
	  test();
	  osDelay(100);
  }
  /* USER CODE END defaultTask */
}

GPDMA configuration:

Timer configuration is the same because basic PWM generations works.

Unfortunately is set 24 different duty cycles in my code and get following result using a oscilloscope:

Any idea why only 14 cycles are outputted?

Best regards
Marko