UART - Sending data from UART2 and receiving data at UART1.

[Sumit Sirmewar]

Hi, I have some problem with UART.

im using stm32l152Vb uC... in that, im suing standard peripheral library...

I configured two uarts (UART1 and UART2) both of them are working in normal mode. I want to send data from PC to mcu-UART2 and after receiving it the same data should be sent to UART1. I cant understand how i wrote code for this... does anyone have idea  ?

[Jack Peacock_2]

Is USART1 operating at a slower, same or faster data rate compared to USART2? A good design will buffer data between RX on USART2 and TX on USART3. What happens if USART3 can't keep up with USART2?

Jack Peacock

[Sumit Sirmewar]

hi @Community member​ ,

as per my application... Im using USART1 and USART2..

i understand ur point..

bt their is some limitations, thats why i cant use usart3,

so can u help me tha, can u tell me how can i ri8 code for Tx data from usart 2 and Rx at Usart 1 and Vice versa?

[Piranha]

Jack already told it - implement data buffering in software and think out how you will handle buffer overflows.

Here are some examples for a decent usage of USART:

https://github.com/MaJerle/stm32-usart-uart-dma-rx-tx

[Sumit Sirmewar]

Hello @Community member​  and @Piranha​ 

i want to send string from USART2 and I have to receive string from USART1 and them interpret it and make other function(s) depends of string. I saw example but that example as based on LL library. Could you tell me how can transmit and receive string ? I want to use interrupt .Please Help

#include "stm32l1xx.h"
#include <stdio.h>
#include <string.h>
 
void uart1_init(void);
void uart2_init(void);
 
char str[20]= "sys reset<CR><LF>";
int i;
char frame_received_fl = 0;
char rx_count = 0;
char tx_buff[100];
char rx_buff[100];
 
int main(void)
{
	uart1_init();
	uart2_init();
	while(1)
	{
		while(USART_GetFlagStatus(USART2,USART_FLAG_TXE)==RESET);
		for(i=0;str[i]!='\0';i++)
		{
			USART_SendData(USART2,str[i]);
			while(USART_GetFlagStatus(USART2, USART_FLAG_TC) == RESET);
		}
		USART_SendData(USART2,'\n');
	}
}
 
void USART1_IRQHandler(void)
{
	if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)//enter interrupt when STM32 receice data.
  {
		USART_ClearITPendingBit(USART1, USART_IT_RXNE);
		rx_buff= USART_ReceiveData(USART1);
		if(rx_buff[rx_count] == 0x0A)
		{
			if(rx_buff[rx_count-1] == 0x0D)
			{
				frame_received_fl = 1;
				rx_count = 0;
			}
	        }
     }
}
 
 
void uart1_init(void)
{
	GPIO_InitTypeDef  GPIO_InitStructure;
	USART_InitTypeDef USART_InitStructure;
	NVIC_InitTypeDef NVIC_InitStructure;
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
 
	GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_6;
	GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
	GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
	GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP;
	GPIO_Init(GPIOB, &GPIO_InitStructure);
 
	GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1);
 
	GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_7;
	GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
	GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
	GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP ;
	GPIO_Init(GPIOB, &GPIO_InitStructure);
 
	GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1);
 
	//USART1->DR = 0 ; 
	
	USART_InitStructure.USART_BaudRate = 9600;
	USART_InitStructure.USART_WordLength = USART_WordLength_8b;
	USART_InitStructure.USART_StopBits = USART_StopBits_1;
	USART_InitStructure.USART_Parity = USART_Parity_No;
	USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
	USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
	
	// Configure USART1 
	USART_Init(USART1, &USART_InitStructure);
 
	//USART1->CR1 |= USART_CR1_RXNEIE | USART_CR1_TXEIE;
	
//	USART1->CR1 |= USART_CR1_RE | USART_CR1_TE | USART_CR1_UE;
	
	////NVIC_EnableIRQ(USART1_IRQn);
	// Enable the USART RX Interrupt 
	USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
	NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);
}
 
 
void uart2_init(void)
{
	 /* Bit configuration structure for GPIOD PIN5 and PIN6 */
  GPIO_InitTypeDef  GPIO_InitStructure;
	 /* USART configuration structure for USART2 */
	USART_InitTypeDef USART_InitStructure;
 
	/* Enalbe clock for USART2, AFIO and GPIOD */
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOD, ENABLE);
 
	/* GPIOD PIN5 alternative function Tx */
	GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_5;
	GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
	GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
	GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP ;
	GPIO_Init(GPIOD, &GPIO_InitStructure);
 
	GPIO_PinAFConfig(GPIOD, GPIO_PinSource5, GPIO_AF_USART2);
 
	/* GPIOD PIN6 alternative function Rx */
	GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_6;
	GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
	GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
	GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP ;
	GPIO_Init(GPIOD, &GPIO_InitStructure);
 
	GPIO_PinAFConfig(GPIOD, GPIO_PinSource6, GPIO_AF_USART2);
 
	//USART2->DR = 0 ; 
 
/* Baud rate 9600, 8-bit data, One stop bit
	No parity, Do both Rx and Tx, No HW flow control*/
	USART_InitStructure.USART_BaudRate = 9600;
	USART_InitStructure.USART_WordLength = USART_WordLength_8b;
	USART_InitStructure.USART_StopBits = USART_StopBits_1;
	USART_InitStructure.USART_Parity = USART_Parity_No;
	USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
	USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
	
	/* Configure USART2 */
	USART_Init(USART2, &USART_InitStructure);
 
	
	USART2->CR1 |= USART_CR1_RE | USART_CR1_TE | USART_CR1_UE;
	
}
 

[Tesla DeLorean]

For interrupts you'd want to look at implementing rings buffers.​

[Tesla DeLorean]

Please refrain from this texting/sms style and use whole English words for business and technical communication.