STM32 UART Interrupt between 2 STM32F103C8 boards.

[RSy.1]

Hello guys good day. I would like to ask for your suggestions regarding the UART interrupt between 2 STM32F103C8 MCUs. I can transmit and receive between 2 MCUs using a single input and output with the use of the IRQHandler. However when I wanted to use the 2nd pin and output I could not transmit and receive anymore. So basically the interrupt is only working for a single inputt/output but for multiple input/output it does not work anymore. I have the codes below:

 // I defined this function before the main
void UARTTX(uint8_t data) 
{
	while(!(USART2 -> SR & USART_SR_TXE));
	USART2 -> DR = data;
}
 
// I defined this function before the main
char UARTRX() 
{
	while(!(USART2 -> SR & USART_SR_RXNE));
	return USART2 -> DR;
}
 
.
.
.
 
 // I enabled these registers before the while loop
USART2 -> CR1 |= USART_CR1_UE; 
USART2 -> CR1 |= USART_CR1_TE;
USART2 -> CR1 |= USART_CR1_RE;
USART2 -> CR1 |= USART_CR1_RXNEIE;
USART2 -> CR1 |= USART_CR1_TXEIE;
 
.
.
.
 
//main code is in the IRQHandler
void USART2_IRQHandler(void) 
{
 HAL_UART_IRQHandler(&huart2);
 {
 //this is first tx output. This code is working only if the second tx output below is not enabled
 if(!HAL_GPIO_ReadPin(BUTTON1_GPIO_Port, BUTTON1_Pin)) 
 {
	USART2 -> DR = 0xFF;																					
 }
 else 
 {
	USART2 -> DR = 0x00;																					
 }
}
	 //this is 2nd tx input and not working 	
//	{
//	 if(HAL_GPIO_ReadPin(BUTTON2_GPIO_Port, BUTTON2_Pin)) 
//	 {
//		USART2 -> DR = 0xF0;																					
//	}
//	else			
//	{
//		USART2 -> DR = 0x0F;																					
//	}
//	}
 
 // this is first rx input and only working if 2nd rx input below is disabled	 
{	
	if(USART2 -> DR == 0xFF) 
	{
		HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_SET);
	}
	else if(USART2 -> DR == 0x00)
	{
		HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_RESET);
	}
}
 
  //this is 2nd rx input and is not working
//	{	
//	if(USART2 -> DR == 0xF0) 
//	{
//	HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, GPIO_PIN_SET);
//	}
//	else if(USART2 -> DR == 0x0F)
//	{
//	HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, GPIO_PIN_RESET);
//	}
//	}	
}
 
 
 

[Tesla DeLorean]

Read the USART2->DR *ONCE* into a variable, and then inspect the variable

The IRQ will occur ONCE for each byte received, if you need to process a sequence, add a state-machine so you can step through the different states as each byte is received.

[RSy.1]

Good day Sir thank you for the answer. I am confused by what you mentioned ONCE. What do you mean by this and how is this written?

[Tesla DeLorean]

It is a register, it does not behave like RAM. Think of it like a ratcheting sprocket, every time you read the content the machine advances.

{

uint8_t dr = USART2 -> DR; // READ IT ONCE

if(dr == 0xFF) // Compare against the local copy

{

HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_SET);

}

else if(dr == 0x00)

{

HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_RESET);

}

}

Also this is really inefficient in a load/store architecture, with volatile register accesses that the compiler/optimize cannot fold

 // I enabled these registers before the while loop

USART2 -> CR1 |= USART_CR1_UE;

USART2 -> CR1 |= USART_CR1_TE;

USART2 -> CR1 |= USART_CR1_RE;

USART2 -> CR1 |= USART_CR1_RXNEIE;

USART2 -> CR1 |= USART_CR1_TXEIE;