Nice, makes sense thanks. Would never occurred me to take a look at first figure if the manual. Now I guess that Figure 23 could also be valid to understand this fact.
I will now share my configuration for a sample demo that captures 8-bit data from GPIOC pins 0-7 when a button connected to TIM1 channel 1 in Input Capture mode (also called Compare in TIM1) is pressed. The program sends through UART the data nicely formatted. When the serial transfer is complete a UART TransferComplete interrupt enables again DMA for a new transfer.
A couple of quirks: if the timer is used just as a mean to trigger DMA or a IC interrupt, it doesn't need to have the clock enabled. Another maybe strange thing is that DMA is configured to move bytes, while the GPIOC IDR register is 32 bit, although 16bits are reserved. The motivation of this choice is that in my application I can use the first 8 contiguous pins as in input. This allows me to use a receiving buffer of bytes, saving memory.
/* USER CODE BEGIN PD */
#define LEN 10
#define TXLEN (LEN * 9) + 2
/* USER CODE END PD */
/* USER CODE BEGIN PV */
uint8_t buff[LEN];
uint8_t txBuff[TXLEN] = { };
uint8_t transferComplete = 0;
/* USER CODE END PV */
/* USER CODE BEGIN PFP */
static void TransferComplete(DMA_HandleTypeDef *DmaHandle);
static void TransferError(DMA_HandleTypeDef *DmaHandle);
static void HalfTransferComplete(DMA_HandleTypeDef *DmaHandle);
/* USER CODE END PFP */
/* USER CODE BEGIN 2 */
// Attach DMA callback functions
htim1.hdma[TIM_DMA_ID_CC1]->XferHalfCpltCallback = HalfTransferComplete;
htim1.hdma[TIM_DMA_ID_CC1]->XferCpltCallback = TransferComplete;
htim1.hdma[TIM_DMA_ID_CC1]->XferErrorCallback = TransferError;
// Start DMA in interrupt mode, specify source and destination
HAL_DMA_Start_IT(htim1.hdma[TIM_DMA_ID_CC1], (uint32_t) &GPIOC->IDR, (uint32_t) buff, LEN);
// Enable timer to trigger DMA transfer - CC1DE bit
__HAL_TIM_ENABLE_DMA(&htim1, TIM_DMA_CC1);
// Enable timer input capture
HAL_TIM_IC_Start(&htim1, TIM_CHANNEL_1);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1) {
if (transferComplete) {
transferComplete = 0;
// Transmit buffer to UART
// Prepare data into buffer
txBuff[0] = '#';
txBuff[1] = '\n';
for (int i = 0; i < LEN; i++) {
for (int k = 0; k < 8; k++) {
uint32_t val = buff[i] & (1u << k);
txBuff[(i * 9) + k + 2] = val == 0 ? '0' : '1';
}
txBuff[(i * 9) + 10] = '\n';
}
HAL_UART_Transmit_IT(&huart2, txBuff, TXLEN);
}
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
// ################################################
// ################################################
/* USER CODE BEGIN 4 */
static void HalfTransferComplete(DMA_HandleTypeDef *DmaHandle) {
HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
}
static void TransferComplete(DMA_HandleTypeDef *DmaHandle) {
HAL_GPIO_TogglePin(LED2_GPIO_Port, LED2_Pin);
transferComplete = 1;
}
static void TransferError(DMA_HandleTypeDef *DmaHandle) {
HAL_GPIO_TogglePin(LED3_GPIO_Port, LED3_Pin);
}
void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart) {
// Enable again DMA for a new transfer
HAL_DMA_Start_IT(htim1.hdma[TIM_DMA_ID_CC1], (uint32_t) &GPIOC->IDR, (uint32_t) buff, LEN);
}
/* USER CODE END 4 */
