STM32F0 Discovery USART example

After a long trail & error finally all the settings for the USART peripheral set correctly and here is a quick tutorial how to do it. Complete Atollic project will be uploaded on my github repository in a days, anyway following this tutorial you should be able to do it. Firstely open Atollic IDE and crate new blank project for your STM32F0 Discovery boar.

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STEP 5

At this point the wizard did the magic and it is time to tweak the main.c the source bellow is the original main.c

**********************************************************************************************************************
/**
** File : main.c
** Abstract : main function.
** Functions : main
** Environment : Atollic TrueSTUDIO(R)
** Distribution: The file is distributed “as is,” without any warranty
** of any kind.
** (c)Copyright Atollic AB.
** You may use this file as-is or modify it according to the needs of your project. This file may only be
** built (assembled or compiled and linked) using the Atollic TrueSTUDIO(R) product. The use of this file
** together with other tools than Atollic TrueSTUDIO(R) is not permitted.
**********************************************************************************************************************
*/

/* Includes */
#include
#include "stm32f0xx_rcc.h"
#include "stm32f0xx_gpio.h"

/* Private typedef */
/* Private define */
/* STM32F0_DISCOVERY board definitions */
#define LED_PORT GPIOC
#define LED1 GPIO_Pin_9
#define LED2 GPIO_Pin_8

#define KEY_PORT GPIOA
#define KEY GPIO_Pin_0

/* Private macro */
/* Private variables */
/* Private function prototypes */
/* Private functions */
/* Global variables */
uint32_t timer=0;
uint8_t timerFlag=0;
/**
**===========================================================================
** Abstract: SysTick interrupt handler
**===========================================================================
*/
void SysTick_Handler(void)
{
timer++;
if (timer>2000)
{
timerFlag = 1;
timer = 0;
}
}
/**
**===========================================================================
** Abstract: main program
**===========================================================================
*/
int main(void)
{
uint32_t ii = 0;
GPIO_InitTypeDef GPIO_InitStructure;

/* TODO - Add your application code here */
SysTick_Config(4800); /* 0.1 ms = 100us if clock frequency 12 MHz */

SystemCoreClockUpdate();
ii = SystemCoreClock; /* This is a way to read the System core clock */
ii = 0;

/* GPIOA-C Periph clock enable */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);

/* Configure
* PA0 USER Button input
* */
GPIO_InitStructure.GPIO_Pin = KEY;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(KEY_PORT, &GPIO_InitStructure);

/* Configure PC8 and PC9 in output pushpull mode
* PC8 = LD3 Green LED
* PC9 = LD4 Blue LED
* */
GPIO_InitStructure.GPIO_Pin = LED1 | LED2;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(LED_PORT, &GPIO_InitStructure);

GPIO_SetBits(LED_PORT, LED1);
GPIO_ResetBits(LED_PORT, LED1);
LED_PORT->BSRR = LED2;
LED_PORT->BRR = LED2;

while (1)
{
if (timerFlag)
{
timerFlag = 0;
ii++;

/* Toggle LED1 */
if (ii == 1)
{
LED_PORT->BSRR = LED1;
}
else if (ii == 2)
{
ii = 0;
LED_PORT->BRR = LED1;
}
}
if(GPIO_ReadInputDataBit(KEY_PORT, KEY))
{
/* USER key pressed */
if (ii == 1)
{
GPIO_SetBits(LED_PORT, LED2);
}
}
else
{
GPIO_ResetBits(LED_PORT, LED2);
}
 }
return 0;
}

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**********************************************************************************************************************

/**

** File : main.c

** Abstract : main function.

** Functions : main

** Environment : Atollic TrueSTUDIO(R)

** Distribution: The file is distributed “as is,” without any warranty

** of any kind.

** (c)Copyright Atollic AB.

** You may use this file as-is or modify it according to the needs of your project. This file may only be

** built (assembled or compiled and linked) using the Atollic TrueSTUDIO(R) product. The use of this file

** together with other tools than Atollic TrueSTUDIO(R) is not permitted.

**********************************************************************************************************************

/* Includes */

#include

#include "stm32f0xx_rcc.h"

#include "stm32f0xx_gpio.h"

/* Private typedef */

/* Private define */

/* STM32F0_DISCOVERY board definitions */

#define LED_PORT GPIOC

#define LED1 GPIO_Pin_9

#define LED2 GPIO_Pin_8

#define KEY_PORT GPIOA

#define KEY GPIO_Pin_0

/* Private macro */

/* Private variables */

/* Private function prototypes */

/* Private functions */

/* Global variables */

uint32_t timer=0;

uint8_t timerFlag=0;

/**

**===========================================================================

** Abstract: SysTick interrupt handler

**===========================================================================

void SysTick_Handler(void)

{

timer++;

if (timer>2000)

{

timerFlag = 1;

timer = 0;

}

/**

**===========================================================================

** Abstract: main program

**===========================================================================

int main(void)

{

uint32_t ii = 0;

GPIO_InitTypeDef GPIO_InitStructure;

/* TODO - Add your application code here */

SysTick_Config(4800); /* 0.1 ms = 100us if clock frequency 12 MHz */

SystemCoreClockUpdate();

ii = SystemCoreClock; /* This is a way to read the System core clock */

ii = 0;

/* GPIOA-C Periph clock enable */

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);

/* Configure

* PA0 USER Button input

* */

GPIO_InitStructure.GPIO_Pin = KEY;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(KEY_PORT, &GPIO_InitStructure);

/* Configure PC8 and PC9 in output pushpull mode

* PC8 = LD3 Green LED

* PC9 = LD4 Blue LED

* */

GPIO_InitStructure.GPIO_Pin = LED1 | LED2;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(LED_PORT, &GPIO_InitStructure);

GPIO_SetBits(LED_PORT, LED1);

GPIO_ResetBits(LED_PORT, LED1);

LED_PORT->BSRR = LED2;

LED_PORT->BRR = LED2;

while (1)

{

if (timerFlag)

{

timerFlag = 0;

ii++;

/* Toggle LED1 */

if (ii == 1)

{

LED_PORT->BSRR = LED1;

}

else if (ii == 2)

{

ii = 0;

LED_PORT->BRR = LED1;

}

if(GPIO_ReadInputDataBit(KEY_PORT, KEY))

{

/* USER key pressed */

if (ii == 1)

{

GPIO_SetBits(LED_PORT, LED2);

}

else

{

GPIO_ResetBits(LED_PORT, LED2);

}

return 0;

}

Add this part to main.c first you need to add usart.h library and add message you will send and add the Send_Byte() function

#include "stm32f0xx_usart.h"

1	#include "stm32f0xx_usart.h"

 /* Private variables */
char MESSAGE[] = "Send a message via UART \r\n";

/* Private function prototypes */

/* Private functions */
void print(USART_TypeDef* USARTx, char* buffer);

/* Private variables */

char MESSAGE[] = "Send a message via UART \r\n";

/* Private function prototypes */

/* Private functions */

void print(USART_TypeDef* USARTx, char* buffer);

/**
**===========================================================================
**
**  Abstract: Send_Byte
**
**===========================================================================
*/
static uint32_t Send_Byte (uint8_t c)
{
    while (USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);
    USART_SendData(USART2, c);
  return 0;
}
/**
**===========================================================================
**
**  Abstract: SendPacket
**
**===========================================================================
*/
void SendPacket(uint8_t *data, uint16_t length)
{
  uint16_t i;
  i = 0;
  while (i < length)
  {
    Send_Byte(data[i]);
    i++;
  }
}

/**

**===========================================================================

** Abstract: Send_Byte

**===========================================================================

static uint32_t Send_Byte (uint8_t c)

{

while (USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);

USART_SendData(USART2, c);

return 0;

}

/**

**===========================================================================

** Abstract: SendPacket

**===========================================================================

void SendPacket(uint8_t *data, uint16_t length)

{

uint16_t i;

i = 0;

while (i < length)

{

Send_Byte(data[i]);

i++;

}

Add USART initialization in the GPIO initialization part (USART2 pins: Rx (PA2) and Tx (PA3))

// USART periferial initialization settings    
  USART_InitTypeDef USART_InitStructure;

  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource2, GPIO_AF_1);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource3, GPIO_AF_1);
  //Configure USART2 pins: Rx (PA2) and Tx (PA3)
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  //Configure USART2 setting: ----------------------------
  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;
  USART_Init(USART2, &USART_InitStructure);
  USART_Cmd(USART2,ENABLE);

// USART periferial initialization settings

USART_InitTypeDef USART_InitStructure;

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource2, GPIO_AF_1);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource3, GPIO_AF_1);

//Configure USART2 pins: Rx (PA2) and Tx (PA3)

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_Init(GPIOA, &GPIO_InitStructure);

//Configure USART2 setting: ----------------------------

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;

USART_Init(USART2, &USART_InitStructure);

USART_Cmd(USART2,ENABLE);

Modify the while(1) routine so when you press the User button on the STM32F0 Discovery board you will see text transmitted from the board.

/* USER key pressed */
          if (ii == 1)
          {
              GPIO_SetBits(LED_PORT, LED2);
              while (USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);
              SendPacket(MESSAGE, 24);
          }

/* USER key pressed */

if (ii == 1)

{

GPIO_SetBits(LED_PORT, LED2);

while (USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);

SendPacket(MESSAGE, 24);

}