HAL_UART_Transmit_IT sending data twice - c

Question

I am trying to establish UART communication between a PC and a STM32f407-DISC1 board using an arduino nano as a middle man.
The PC sends 'r' to the arduino to indicate a request.
The request is then communicated to the stm32 with a GPIO interrupt, which then should be transmitting 480 bytes of data using HAL_UART_Transmit_IT.
It however sends the data twice, with only a single request made.
The code on the STM32 is generated by STM32CubeMX
Data request made by the arduino
void loop() {
digitalWrite(4, 0); // Clear EXTI11 line.
if (mySerial.available() && received < 480) { // STM32 sending data and is not done.
buff[received] = mySerial.read(); // Append received data to the buffer.
received++;
}
if (received >= 480) { // If the buffer is full
received = 0; // transmit it to PC.
Serial.println(buff);
}
if (Serial.available()) {
if (Serial.read() == 'r') { // PC requests data from the STM32
digitalWrite(4, 1); // Triggers STM32 EXTI11 line.
while (Serial.available()) // Empty the buffer.
Serial.read();
}
}
}
data transmission on the STM32
void EXTI15_10_IRQHandler(void)
{
// Make sure that the interrupt is the good one.
if (HAL_GPIO_ReadPin(data_req_IRQ_GPIO_Port, data_req_IRQ_Pin)) {
if (is_sending_data == FALSE) // If no transmission is happening
should_send_data = TRUE; // raise transmission flag.
}
// IRQ handling stuff...
}
void HAL_UART_TxCpltCallback(UART_HandleTypeDef * huart) {
is_sending_data = FALSE; // Transmition is completed, unblock requests.
}
void main(void){
// Init and other stuff...
while (1) {
if (should_send_data == TRUE) { // If data was requested
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_RESET);
HAL_UART_Transmit_IT(&huart3, matrice, 480); // Start transmission by interrupt.
is_sending_data = TRUE; // Block requests.
should_send_data = FALSE; // Clear flag.
}
// matrice acquisition stuff here
}
}

Answer 1

Alright so I found a solution, but it involved just rethinking my approach, so sorry for those looking for an answer to this problem.
I removed the arduino middle man by replacing it with a USB to RS232 converter and made UART reception work by interrupt. The STM detects the 'r' character which triggers the data communication.
Here is the interrupt part:
void USART3_IRQHandler(void)
{
if (USART3->SR & UART_IT_RXNE) { // If a byte is received
rxBuff[0] = (uint8_t) (huart3.Instance->DR & (uint8_t) 0xFF); // Read it.
__HAL_UART_FLUSH_DRREGISTER(&huart3); // Clear the buffer to avoid errors.
rx_new_char_flag = TRUE; // Raise the new_char flag.
return; // Stops the IRQHandler from disabling interrupts.
}
}
and the gestion of that in the main
while (1) {
if (rx_new_char_flag == TRUE) {
rx_new_char_flag = FALSE;
if (rxBuff[0] == 'r') {
rxBuff[0] = 0;
HAL_UART_Transmit_IT(&huart3, matrice, 480); // Start transmission by interrupt.
}
}
On the PC side, to optimize performance, instead of waiting for the full 480 bytes, I wait for only one character, if one is received I keep reading the serial port, as shown in the code bellow
int i = 0;
do {
ReadFile(m_hSerial, &temp_rx[i], 1, &dwBytesRead, NULL);
i++;
} while (dwBytesRead > 0 && i < 480);
for (int j = i; j < 480; j++) // If the transmission is incomplete, fill the buffer with 0s to avoid garbage data.
temp_rx[j] = 0;
if(i>=480) // If all the bytes has been received, copy the data in the working buffer.
std::copy(std::begin(temp_rx), std::end(temp_rx), std::begin(m_touch_state));
This works well with pretty decent performance, so that may be a permanent solution to my problem.