STM32F0 UART not working

Question

I'm new in ST world. I'm trying to work with UART, so I wrote this code to initializate UART and to send "Hello". I'am using STM32F0 board.

#include "stm32f0xx_gpio.h"
#include "stm32f0xx_rcc.h"
#include "stm32f0xx_misc.h"
#include "stm32f0xx_usart.h"

#define UINT8               uint8_t
#define UINT32              uint32_t


#define MAX_BUFFER_SIZE     256

typedef struct Buffer_st
{
   UINT8 size;
   UINT8 data[MAX_BUFFER_SIZE];
}Buffer_st;

Buffer_st receivedDataUART1;

void initUART1(UINT32 baudRate)
{
   NVIC_InitTypeDef NVIC_InitStructure;
   GPIO_InitTypeDef GPIO_InitStructure;
   USART_InitTypeDef USART_InitStructure;

   /* Enable the USART1 Interrupt */
   NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
   NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);

   //UART init
   USART_InitStructure.USART_BaudRate = baudRate;
   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;

   /* Enable GPIO clock */
   RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

   /* Enable USART clock */
   RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);

   /* Connect PXx to USARTx_Tx */
   GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1);

   /* Connect PXx to USARTx_Rx */
   GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1);

   /* Configure USART Tx, Rx as alternate function push-pull */
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;
   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
   GPIO_Init(GPIOA, &GPIO_InitStructure);

   /* USART configuration */
   USART_Init(USART1, &USART_InitStructure);

   /* Enable USART */
   USART_Cmd(USART1, ENABLE);
   USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);

   resetReceivedDataBufferUART1();
}

void resetReceivedDataBufferUART1(void)
{
   receivedDataUART1.size = 0;
   memset(receivedDataUART1.data, MAX_BUFFER_SIZE, 0);
}

UINT8 sendDataUART1(Buffer_st buffer)
{
  UINT8 cpt;

  for (cpt = 0; cpt < buffer.size; cpt++)
  {
     USART_SendData(USART1, buffer.data[cpt]);

     //Loop until the end of transmission
     while (USART_GetFlagStatus(USART1, USART_IT_TXE) == RESET);
  }
}

void USART1_IRQHandler(void)
{
   if (USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)
   {
       receivedDataUART1.data[receivedDataUART1.size++] = USART_ReceiveData(USART1);
   }
}

int main(void)
{
   Buffer_st buffer = {6,"Hello"};

   initUART1(9600);
   sendDataUART1(buffer);

   while(1);
   return 0;
}

I'am using UART/USB connector. The problem is that I don't receive any thing in minicom. When debugging I found that progrom enter in infinite loop

 //Loop until the end of transmission
while (USART_GetFlagStatus(USART1, USART_IT_TXE) == RESET);

Answer 1

You are mixing up interrupt status flags with the flags used for synchronous polling. To send data you must first poll the USART_FLAG_TXE flag for the transmit data register empty status and then you can send your byte. The USART_IT_TXE flag is for interrupt use only.

So, to send a byte, do something like this:

while(USART_GetFlagStatus(USART1,USART_FLAG_TXE)!=SET);
USART_SendData(USART1,myByte);

Please see the documentation for the USARTx_ISR register in RM0091 for further information.