Programming Example : USART

#include "stm32f2xx.h"

void GPIO_Config_AFMode(void);
void USART3_Config(void);

int main(void)
{

  GPIO_Config_AFMode();

  USART3_Config();

  while (1)
  {
    USART_SendData(USART3, 0xA5);
    while (USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET);
  }
}

void GPIO_Config_AFMode(void)
{

  GPIO_InitTypeDef GPIO_InitStructure;

  /* Enable GPIOC Clock */

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

  /* Connect PC10, PC11 to USART3_Tx, USART3_Rx */

  GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_USART3);

  GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_USART3);

  /* Configure USART3_Tx and USART3_Rx as alternative function */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;

  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(GPIOC, &GPIO_InitStructure);

}

void USART3_Config(void)
{
  USART_InitTypeDef USART_InitStructure;

  /* Enable USART3 Clock */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);

  /* Configure USART3 */
  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(USART3, &USART_InitStructure);

  /* Enable USART3 */
  USART_Cmd(USART3, ENABLE);
}


/*
<USART Configuration>

1. USART Clock Enable
@reg   RCC->AHB1ENR
@fn    void RCC_APB1PeriphClockCmd(uint32_t RCC_APB1Periph, FunctionalState NewState)
@param RCC_APB1Periph_USART3, ENABLE
@ref   stm32f2xx_rcc.h, stm32f2xx.h

2. Configure USART port (1) Word length, Parity, Mode

@reg   USARTx->CR1

@desc  Bit 12, M: Word length bits, 

       Bit 10, PCE: Parity control enable (by Hardware), 

       Bit 9, PS: Parity Selection (Even / Odd),

       Bit 3, TE: Transmitter enable,

       Bit 2, RE: Receiver enable      

@param USART_WordLength_8b, USART_Parity_No, USART_Mode_Rx, USART_Mode_Tx

@ref   stm32f2xx_usart.h

3. Configure USART port (2) Stop bits
@reg   USARTx->CR2
@desc   Bits 13:12, STOP: STOP bits configuration
@param USART_StopBits_1
@ref   stm32f2xx_usart.h

4. Configure USART port (3) Hardware flow control

@reg   USARTx->CR3
@desc  Bit 9, CTSE: CTS enable
       Bit 8, RTSE: RTS enable
@param USART_HardwareFlowControl_None
@ref   stm32f2xx_usart.h

5. Configure USART port (4) Baudrate

@reg   USARTx->BRR

@desc  Bits 15:4, DIV_Mantissa[11:0]: Mantissa of USARTDIV
       Bits 3:0, DIV_Fraction[3:0]: Fraction of USARTDIV

@param USART_CR1_OVER8 (Oversampling)

@ref   stm32f2xx_usart.h

6. USART enable

@reg   USARTx->CR1

@desc  Bit 13, UE: USART enable

@param USART_CR1_UE

@ref   stm32f2xx_usart.h

<USART Data Transmission>

1. USART Send Data

@reg   USARTx->DR

@desc  Bits 8:0, DR[8:0]: Data value to send or receive

@fn    void USART_SendData(USART_TypeDef* USARTx, uint16_t Data)

@param USART3

@ref   stm32f2xx.h

2. USART Check Status

@reg   USARTx->SR

@desc  Bit 6, TC: Transmission complete

@fn    FlagStatus USART_GetFlagStatus(USART_TypeDef* USARTx, uint16_t USART_FLAG)

@param USART3, USART_FLAG_TC

@ref   stm32f2xx.h, stm32f2xx_usart.h

*/