Electronic – STM32 SRAM to DMA GPIO pins

dmastm32

I wish to transfer a large array of data to 8 output pins that are all on the same port. E.g. a 500 element 8bit array where each bit of each element represents the pin status.
So 500 independent transfers to the port would be required.

I have been looking through the examples that ST have but none of them seem to do this.
There seems to be a lot of 'DMA to PWM' examples which transfer to a pin that has a timer connected to it but this isn't useful to me since I want to transfer to a whole port.
How would I do this? Are there any examples similar to this which I could modify to my need?

Thanks

Best Answer

Short description:

Timer trig DMA with desired speed, DMA write data to GPIO output register.

Long description:

  1. Prepare selected GPIO port output state to default state low/high
  2. Configure selected GPIO port PX to output push-pull/open drain
  3. Configure any timer to desired period of GPIO port updating
  4. Configure selected DMA and link it to selected TIM
  5. Configure callbacks for DMA IRQs: HT, TC, ERR
  6. Enable DMA for write you data buffer, buffer length to selected PX->ODR
  7. Enable TIM to generate DMA events
  8. Run TIM
  9. Handle DMA state in callbacks and control TIM as you need

Code blank:

All code written right here and not tested, it may content simple mistakes such as using variable instead it pointer in HAL macros or functions calls.

GPIO_InitTypeDef GPIO_InitStruct;
TIM_HandleTypeDef htim1;
DMA_HandleTypeDef hdma_tim1_uev;

/* 1 (Port GPIOA) */
__HAL_RCC_GPIOA_CLK_ENABLE();
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_All, GPIO_PIN_RESET);

/* 2 (Port GPIOA) */
GPIO_InitStruct.Pin = GPIO_PIN_All;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

/* 3 (Timer TIM1) */
__HAL_RCC_TIM1_CLK_ENABLE();
htim1.Instance = TIM1;
htim1.Init.Prescaler = DESIRED_PRESCALER;
htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
htim1.Init.Period = DESIRED_PERIOD;
htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim1.Init.RepetitionCounter = 0;
HAL_TIM_Base_Init(&htim1)

/* 4 (DMA1 Channel2) */
__HAL_RCC_DMA1_CLK_ENABLE();
hdma_tim1_uev.Instance = DMA1_Channel2;
hdma_tim1_uev.Init.Direction = DMA_MEMORY_TO_PERIF;
hdma_tim1_uev.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_tim1_uev.Init.MemInc = DMA_MINC_ENABLE;
hdma_tim1_uev.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD; // 16 bits
hdma_tim1_uev.Init.MemDataAlignment = DMA_PDATAALIGN_HALFWORD;
hdma_tim1_uev.Init.Mode = DMA_NORMAL;
hdma_tim1_uev.Init.Priority = DMA_PRIORITY_LOW;
HAL_DMA_Init(&hdma_tim1_uev);
__HAL_DMA1_REMAP(HAL_DMA1_CH2_TIM1_UP);
__HAL_LINKDMA(&htim1,hdma[TIM_DMA_ID_UPDATE],hdma_tim1_uev);
HAL_NVIC_SetPriority(DMA1_Ch2_3_DMA2_Ch1_2_IRQn, 0, 0); // enable DMA IRQ
HAL_NVIC_EnableIRQ(DMA1_Ch2_3_DMA2_Ch1_2_IRQn);

/* 5 (Callbacks for DMA IRQs) */
htim->hdma[TIM_DMA_ID_UPDATE]->XferCpltCallback = data_tramsmitted_handler;
htim->hdma[TIM_DMA_ID_UPDATE]->XferErrorCallback = transmit_error_handler;

/* 6 (Enable DMA) */
HAL_DMA_Start_IT(htim1.hdma[TIM_DMA_ID_UPDATE],(uint32_t)&my_data_buf, 
    (uint32_t)&GPIOA->ODR, my_data_buf_length);

/* 7 (Enable TIM for DMA events) */
__HAL_TIM_ENABLE_DMA(&htim1, TIM_DMA_UPDATE);

/* 8 (Run TIM) */
__HAL_TIM_ENABLE(&htim1);

/* 9 (DMA IRQ callbacks) */
void data_tramsmitted_handler(DMA_HandleTypeDef *hdma)
{
    /* Stop timer */
    __HAL_TIM_DISABLE(&htim1);
    /* Reconfigure DMA */
    HAL_DMA_Start_IT(htim1.hdma[TIM_DMA_ID_UPDATE],(uint32_t)&my_data_buf, 
        (uint32_t)&GPIOA, my_data_buf_length);
    /* Start timer for new data transmit */
    __HAL_TIM_ENABLE(&htim1);
}

void transmit_error_handler(DMA_HandleTypeDef *hdma)
{
    /* Stop timer */
    __HAL_TIM_DISABLE(&htim1);
    /* Some error handle ? */
}
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