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Problem receiving data on USART1

Question asked by Tom on Jul 18, 2012
Latest reply on Jul 18, 2012 by Clive One
Hello,
I am using the STM32L-Discovery board and try to transmit / receive data via USART1.
My problem is that the controller does nor react on data sent from the PC, but if I send one byte from the controller the "USART_GetFlagStatus(USART1, USART_FLAG_RXNE)" reports new received data.
The behaviour of the code below is that the controller sends "0x41 0x00" every time the Sys-Timer-Interrupt occurs because it seems to receive every time the 'A' is sent and the (not really received) data is echoed.

Can anybody help please ?

Regards
Tom

This is my code:

#include "stm32l1xx.h"
 
/* function prototypes */
void RCC_Configuration(void);
void GPIO_Configuration(void);
void NVIC_Configuration(void);
void USART1_Configuration(void);
void TIM2_Configuration(void);
void SysTick_Handler(void);
void TIM2_IRQHandler(void);
void USART1_Send(char cData);
int iTick = 0;
 
int main(void)
{
    char data;
    SystemInit();
    RCC_Configuration();
    NVIC_Configuration();
    GPIO_Configuration();
    USART1_Configuration();
    TIM2_Configuration();
 
    // Init SysTick Timer
    SysTick_Config(1000000);
 
    while(1)
    {
            if (iTick != 0)
            {
                iTick = 0;
                USART1_Send('A');
            }
            if (USART_GetFlagStatus(USART1, USART_FLAG_RXNE)!= RESET)
            {
                data=(uint8_t)USART_ReceiveData(USART1);
                //echo
                USART1_Send(data);
                USART_ClearFlag(USART1, USART_FLAG_RXNE);
                GPIOB->ODR ^= GPIO_Pin_7;
            }
 
    }
}
 
void USART1_Send(char cData)
{
    USART_SendData(USART1, cData);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
}
 
void RCC_Configuration(void)
{
    // Enable GPIOA, GPIOB clock
    RCC_AHBPeriphClockCmd (RCC_AHBPeriph_GPIOA | RCC_AHBPeriph_GPIOB, ENABLE);
    // Enable TIM2 clock
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    // Enable USART1 clock
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
}
 
void NVIC_Configuration(void)
{
    NVIC_InitTypeDef NVIC_InitStructure;
    // Place the vector table into FLASH
    NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
    //
    //NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
 
    //enable tim2 irq
    NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
 
 
}
 
void  SysTick_Handler(void)
{
    iTick = 1;
}
 
void GPIO_Configuration(void)
{
    // Initialize Leds mounted on STM32 board
    GPIO_InitTypeDef  GPIO_InitStructure;
 
    // Configure the GPIO_LED pin
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
 
    // Configure USART1 Rx (PA10) as input
    GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
 
    // Configure USART1 Tx (PA9) as alternate function
    GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
 
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);
 
}
 
void USART1_Configuration(void)
{
    USART_InitTypeDef USART_InitStructure;
    USART_ClockInitTypeDef USART_ClockStructure;
 
    /* USART1 configured as follow:
          - BaudRate = 115200 baud
          - Word Length = 8 Bits
          - One Stop Bit
          - No parity
          - Hardware flow control disabled (RTS and CTS signals)
          - Receive and transmit enabled
          - USART Clock disabled
          - USART CPOL: Clock is active low
          - USART CPHA: Data is captured on the middle
          - USART LastBit: The clock pulse of the last data bit is not output to
                           the SCLK pin
    */
    USART_InitStructure.USART_BaudRate            = 115200;
    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_Rx | USART_Mode_Tx;
    USART_Init(USART1, &USART_InitStructure);
 
    USART_ClockStructure.USART_Clock = USART_Clock_Enable;
    USART_ClockInit(USART1, &USART_ClockStructure);
 
    USART_Cmd(USART1, ENABLE);
}
 
 
 
void TIM2_Configuration(void)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    //setting timer 2 interrupt to ??hz ((??/1000)*1000)s
    TIM_TimeBaseStructure.TIM_Prescaler = 1000 ;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_Period = 1000-1;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
    /* TIM IT enable */
    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
 
    /* TIM2 enable counter */
    TIM_Cmd(TIM2, ENABLE);
 
}
//timer 2 interrupt
void TIM2_IRQHandler(void)
{
    //if interrupt happens the do this
    if(TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
        //clear interrupt and start counting again to get precise freq
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
        //toggle led to see some chance in port B pin 6
        if(GPIO_ReadOutputDataBit(GPIOB,GPIO_Pin_6) == RESET)
            GPIO_WriteBit(GPIOB,GPIO_Pin_6,SET);
        else
            GPIO_WriteBit(GPIOB,GPIO_Pin_6,RESET);
    }
}

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