Uart1 not waiting to receive all characters

[dvcosta43]

Posted on July 14, 2014 at 15:14

This is my first post here as I'm really stuck. I'm using a stm32F103 device but I cannot seem to get the usarts configured correctly to receive data. Transmit is fine, and on the receive side I do see characters. I want the user to enter a correct string terminated with a '\r' before the main app continues. However the uart only waits for me to type in some of the characters. It never waits to see in carraige return is pressed.

What I need is for the app to wait in the character receive loop until CR is pressed. If the key is invalid, then the user is prompted to re-enter the key. If not move on. Thanks in advance Dave     void Usart1Init(void)     { USART_InitTypeDef USART_InitStructure; GPIO_InitTypeDef GPIO_InitStructure;          NVIC_InitTypeDef NVIC_InitStructure;                    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA , ENABLE);         RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);          /*-------------------------- GPIO Configuration ----------------------------*/          GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;                GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;   GPIO_Init(GPIOA, &GPIO_InitStructure);              GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;               GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;   GPIO_Init(GPIOA, &GPIO_InitStructure);                     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_Rx | USART_Mode_Tx;        COMInit(COM1, &USART_InitStructure);   USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);             } void USART1_IRQHandler(void) {   if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)   {                    printf(''\r\nEnter Key \r\n'');                  res = Check_Key();                               if (res == 1)              {                         printf(''\r\nCorrect Key \r\n'');                 }             } } uint8_t Check_Key(void) { char rxbyte;   static uint8_t val = 0;     static uint8_t char_count= 0; static char str_fr[20];             while (USART_GetFlagStatus(USART1, USART_FLAG_RXNE) == RESET);    rxbyte = USART_ReceiveData(USART1);                            str_fr[char_count] = (uint8_t)rxbyte;    printf(''*'');      char_count++;           if (rxbyte == '\r')  // Detect a newline character   {           if (!strcmp(str_fr, ''Hello+Welcome\r''))         {                 val = 1;       }                          else         {           printf(''\n\rInvalid Key\n\r'');             char_count= 0;                 }     }                    return val;         }

[Tesla DeLorean]

Posted on July 14, 2014 at 15:36

Ok, have your interrupt receive one character at a time, and don't output multiple characters via printf(), etc.

Understand that it the time it takes to send a character you can also receive one, if you send a dozen and don't service the received data you will likely miss them.

[dvcosta43]

Posted on July 14, 2014 at 16:32

Hello Clive,

I thought I was receiving only one character at a time. Where in the code states otherwise? Removing all printfs make no difference. Should UART not wait in the receive loop until CR is pressed? Dave

[dvcosta43]

Posted on July 14, 2014 at 17:08

Clive,

I think I'm sorted on this one. Thanks for your help. Dave

[Tesla DeLorean]

Posted on July 14, 2014 at 17:15

I scanned the code, the while loop seemed problematic, watch that the debugger doesn't clear the peripheral status.

Make sure you NUL terminate strings before using library functions against them.