How to use TIMER event DMA from Memory to GPIO

[Mnemocron]

My goal is to send bit patterns from an array directly to GPIO, using a Timer as a sample clock / DMA trigger.

More concretely: TIM2 Update Event --> DMA --> memory to GPIO Port ODR transfer

I am on STM32f103rb (Nucleo-64)

Similar questions have been asked here, of which none helped me so far.

https://community.st.com/s/question/0D53W000003yufESAQ/how-to-setup-dma-to-gpio-transfer-using-hal-in-the-cubeidemy-goal-is-to-transfer-the-contents-of-an-integer-array-8-bits-per-value-to-8-gpio-pins

https://community.st.com/s/question/0D50X0000C7eDobSQE/dma-gpio-stm32f103

I use the following initialization of the TIM2 peripheral and the code below to start the DMA. Pins PC0 to PC3 are configured as outputs.

On the oscilloscope I get the TIM2_CH1 Output Compare signal at 500 Hz.

But the DMA does not affect the GPIOC->ODR state. Why?

 

 

/* USER CODE BEGIN 2 */
  uint16_t pixelclock[8] = {0xffff, 0xffff, 0x0000, 0x0000, 0xffff, 0x0000, 0xffff, 0x0000};
 
  HAL_DMA_Start(&hdma_tim2_up,  (uint32_t)pixelclock, (uint32_t)&(GPIOC->ODR), 8);
 
  HAL_TIM_Base_Start(&htim2);
  HAL_TIM_OC_Start(&htim2, TIM_CHANNEL_1);
  /* USER CODE END 2 */

Debugger state:

 

[TDK · Accepted solution]

HAL isn't set up to do this, but it can be done.

Ensure UDE is set in TIMx_DIER. If that's not it, show the contents of the TIM2 registers.

[Mnemocron]

That was it!

Thank you so much 🙂

[TDK]

Glad to help. Consider using the GPIOx_BSRR register instead (with 32-bit words) in order to change only PC0-PC3 and leave PC4-PC15 alone.

[Mnemocron]

Done! Thanks for all the hints. For anyone looking for the full code:

https://github.com/mnemocron/STM32_PatternDriver