STM32 Use DMA to generate bit pattern on GPIO PIN - stm32

Question

I am trying to generate a bit pattern on a GPIO pin. I have set-up the DMA engine to transfer from an array of GPIO pin states to the GPIO BSRR register
Here is the code I am using to configure the DMA
hdma_tim16_ch1_up.Instance = DMA1_Channel3;
hdma_tim16_ch1_up.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_tim16_ch1_up.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_tim16_ch1_up.Init.MemInc = DMA_MINC_ENABLE;
hdma_tim16_ch1_up.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
hdma_tim16_ch1_up.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
hdma_tim16_ch1_up.Init.Mode = DMA_NORMAL;
hdma_tim16_ch1_up.Init.Priority = DMA_PRIORITY_LOW;
if (HAL_DMA_Init(&hdma_tim16_ch1_up) != HAL_OK)
{
Error_Handler();
}
/* Several peripheral DMA handle pointers point to the same DMA handle.
Be aware that there is only one channel to perform all the requested DMAs. */
__HAL_LINKDMA(tim_baseHandle,hdma[TIM_DMA_ID_CC1],hdma_tim16_ch1_up);
__HAL_LINKDMA(tim_baseHandle,hdma[TIM_DMA_ID_UPDATE],hdma_tim16_ch1_up);
Here is the code I use to setup the transfer:
uint32_t outputbuffer[] = {
0x0000100,0x01000000,
0x0000100,0x01000000,
0x0000100,0x01000000,
0x0000100,0x01000000,
0x0000100,0x01000000,
0x0000100,0x01000000,
0x0000100,0x01000000
/* ... */
};
if (HAL_DMA_Start_IT(htim16.hdma[TIM_DMA_ID_UPDATE], (uint32_t)outputbuffer, (uint32_t)&GPIOG->BSRR, 14) != HAL_OK)
{
/* Return error status */
return HAL_ERROR;
}
__HAL_TIM_ENABLE_DMA(&htim16,TIM_DMA_UPDATE);
HAL_TIM_Base_Start_IT(&htim16);
I am expecting to see every time the counter overflows, the DMA transfers 32 bits from the array and increments to the next array position until the DMA CNDTR register reads 0.
I set up a GPIO pin to toggle every time the timer over flows and I setup an alternating bit pattern in the array. I would expect the two GPIO pins to be similar in their output shape but I get one longer pulse on the line connected to the DMA. Any tips would be greatly appreciated

Answer 1

configure TIM2 as input capture direct mode (TIM2_CH1)
configure TIM2 DMA direction "memory to peripheral"
configure TIM2 data width Half word / Half word
configure GPIO pins as GPIO_OUTPUT, for example 16 pins GPIOD0..GPIOD15
copy and paste HAL_TIM_IC_Start_DMA() function from HAL library and give it a new name MY_TIM_IC_Start_DMA()
find HAL_DMA_Start_IT() function call in MY_TIM_IC_Start_DMA()
replace (uint32_t)&htim->Instance->CCR1 with (uint32_t)&GPIOD->ODR
if (HAL_DMA_Start_IT(htim->hdma[TIM_DMA_ID_CC1], (uint32_t)&GPIOD->ODR, (uint32_t)pData, Length) != HAL_OK)
Now you can start DMA to GPIO transfer by calling
MY_TIM_IC_Start_DMA(&htim2, TIM_CHANNEL_1,(uint32_t*)gpioBuffer,GPIO_BUFFER_SIZE);
Actual transfer must be triggered by providing pulses on TIM2_CH1 input pin (for example, by using output compare pin from other timer channel). Those pulses originally was used to save Timer2 CCR1 register values to DMA buffer. Code was tweaked to transfer DMA buffer value to GPIOD ODR register.
For GPIO to Memory transfer change TIM2 DMA direction to "peripheral to memory", configure GPIO pins as GPIO_INPUT and use GPIOD->IDR instead of ODR in HAL_DMA_Start_IT parameters in modified MY_TIM_IC_Start_DMA() function.