about gpdma transmission size

[dh_leslie]

I am porting code from G473 to U575 because I need more flash and ram.

Then I meet some issues on gpdma transmission size.

For G473, I use dma to transfer data to timer ARR likes:

uint16_t buf[65536] = { ..... };

HAL_TIM_Base_Start_DMA(&htim1, (uint32_t *)buf, 65536);

For U575, the code doesn't work because the size have to be 65536 * sizeof(uint16_t), not the number of buf.

Is there any way to figure it out?

[TDK · Accepted solution]

The code presented cannot work, either at 65536 or at 65536 * sizeof(uint16_t).

The CNDT register field is 16 bits and accept a maximum value of 65535.

The HAL_TIM_Base_Start_DMA also accept a max value of 65535.

/**
  * @brief  Starts the TIM Base generation in DMA mode.
  * @PAram  htim TIM Base handle
  * @PAram  pData The source Buffer address.
  * @PAram  Length The length of data to be transferred from memory to peripheral.
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_TIM_Base_Start_DMA(TIM_HandleTypeDef *htim, const uint32_t *pData, uint16_t Length)
{

[dh_leslie]

Yes, you are right.

Currently, I only use 16384 in G473. But I want to port code to U575 and use more buf in DMA.

And I found the definition is different between G4 and U5 in DMA size.

[TDK]

> And I found the definition is different between G4 and U5 in DMA size.

No it's not.

https://github.com/STMicroelectronics/stm32u5xx-hal-driver/blob/819eaeffea70bb4bc2319111ea0fcc21c9788189/Src/stm32u5xx_hal_tim.c#L541

https://github.com/STMicroelectronics/stm32g4xx-hal-driver/blob/1a4f1ca138a19dfe42becc50975f11a1e7554e31/Src/stm32g4xx_hal_tim.c#L541

[dh_leslie]

In G473, the code below is ok.

uint16_t buf[4] = { ..... };

HAL_TIM_Base_Start_DMA(&htim1, (uint32_t *)buf, 4);

I tried this in U575, buf[2] and buf[3] will not be transfered，unless I set the size = 4 * sizeof(uint16_t).