Firmware Course Review - 02.2. UART

1. Title

LED BUTTON CONTROL using UART

2. Category

"STM32", "Firmware"

 

3. Key Concepts

"UART"
In STM32, UART Receive (Rx) is managed through an interrupt-based mechanism (HAL_UART_Receive_IT) to receive data asynchronously, storing incoming bytes in buffer without blocking the CPU.
The HAL_UART_RxCpltCallback is executed when a UART receive interrupt occurs for the specified *huart.

Transmit (Tx) functionality in STM32 UART also operates on the same interrupt-driven principle as receive (Rx).

 

4. Setup

9600 Baudrate UART 설정

Interrupt 설정

 

 

5. Code Review

 

UART_HandleTypeDef huart2;
HAL_UART_Receive_IT(&huart2, &rx_data, 1);	//	UART 인터럽트 시작 구현, uart로 받은 데이터를 rx_data로 저장

Initializes the UART interrupt reception, configuring huart2 to store received UART data into the variable rx_data one byte at a time.

 

 

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)		//		UART Call Back 함수 구현.
{
	volatile static int i = 0;

	if(huart == &huart2)
	{
		uint8_t data;
		data = rx_data;

		if(data == '\n')
			{
			rx_buffer[rear][i++] = '\0';	//	strncpy 사용 시, 문자열의 끝은 NULL이여야 복사가 가능하기 때문에 NULL 문자를 끝에 추가해준다.
			i = 0;
			rear++;
			rear %= COMMAND_NUMBER;
			}

		else
			{
			rx_buffer[rear][i++] = data;
			}

	}
	HAL_UART_Receive_IT(&huart2, &rx_data, 1);	//	UART2의 다음 Interrupt를 받기 위해 해당 함수를 실행한다.
}

UART receive callback function, HAL_UART_RxCpltCallback, which is triggered upon receiving data via UART. It processes incoming data into a circular buffer (rx_buffer) and re-enables the interrupt to continue receiving subsequent data.

** UART 송신시 일반적으로 \n, \0, \r, 또는 특정 종료 코드가 사용된다. 이 코드에서는 \n을 감지하여 데이터 송신이 끝난 것을 확인함!

 

void pc_command_processing(void)
{
	if (front != rear)
	{
		if (strncmp(rx_buffer[front], "on_led", strlen("on_led")) == 0)
		{
			func_index=0;
		}
		else if((strncmp(rx_buffer[front], "off_led", strlen("off_led")) == 0))
		{
			func_index=1;
		}
     .
     .
     .
     }
 }

pc_command_processing, checks for new commands in the circular buffer (rx_buffer) and parses them using string comparison. Based on the command, it sets func_index to the corresponding function index for execution.

 

 

6. Testing and Debugging

* Testing Tools: STM32 CUBE IDE, NUCLEO-F411RE, Oscilloscope

 

UART, BUTTON 동시 동작

"97" 신호 UART 분석