STM32F030_USART detailed configuration description

The serial port is the most frequently used problem in programming. It is usually used to send and receive data. At the same time, it has another function - to detect whether the program is correct. The STM32F030 series microcontroller naturally has a serial port. This article mainly introduces several commonly used simple applications of STM32F030_USART and its functional configuration.

1 Overview

The Universal Synchronous Asynchronous Receiver/Transmitter (USART) provides a flexible way for the MCU to communicate with external devices in full-duplex asynchronous serial data in the form of industrial standard NRZ. The USART can use a fractional baud rate generator to provide an ultra-wide baud rate setting range. DMA can be used to implement multi-buffer settings to support high-speed data communication.

• Full-duplex, asynchronous communication

• Configurable 16x or 8x oversampling method provides flexible choice between speed and clock tolerance

• Fractional Baud Rate Generator

• Automatic baud rate detection

• Single-line half-duplex communication

• The number of stop bits can be set - supports 1 or 2 stop bits

• Fourteen interrupt sources and interrupt flags 
  - CTS toggle 
  - LIN break detect 
  - Transmit data register empty 
  - Transmit complete 
  - Receive data register full 
  - Line idle detected 
  - Overrun error 
  - Framing error 
  - Noise error 
  - Parity error 
  - Address/character match 
  - Receive timeout interrupt 
  - Block end interrupt 
  - Wake-up from Stop mode

• Parity control: 
  - Send parity bit 
  - Receive parity check

2. Preparation

1. Read the STM32F030x data sheet carefully

2. Understand the operation principle of USART

3. View the STM32F030 development board schematics and package diagrams

4. The computer is equipped with keil and other compilation software

3. Register Description

Control Register 1 (USART_CR1) 
 
 
 
Control Register 2 (USART_CR2) 
 
 
 
 
 
Control Register 3 (USART_CR3) 
 
 
 
 
Baud Rate Register (USART_BRR) 
 
Guard Time and Prescaler Register (USART_GTPR) 
 
Interrupt and Status Register (USART_ISR) 
 
 
 
 
 
 
Interrupt Flag Clear Register (USART_ICR) 
 
 
Data Receive Register (USART_RDR) 
 
Data Transmit Register (USART_TDR) 

4. USART Configuration

1. USART Schematic 
   

   

2. USART code analysis①USART 
   initialization

void Usart_Init(uint32_t BaudRate)
{
    USART_InitTypeDef USART_InitStruct;
    GPIO_InitTypeDef GPIO_InitStruct;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE);

    /*
    PA9-TX-Push-Pull Multiplexing
    PA10-RX-Floating input/pull-up input
    */
    GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_1);
    GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_1);  

    GPIO_InitStruct.GPIO_Pin=GPIO_Pin_9;
    GPIO_InitStruct.GPIO_Mode=GPIO_Mode_AF;
    GPIO_InitStruct.GPIO_OType=GPIO_OType_PP;
    GPIO_InitStruct.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_Init(GPIOA,&GPIO_InitStruct);

    GPIO_InitStruct.GPIO_Pin=GPIO_Pin_10;
    GPIO_InitStruct.GPIO_Mode=GPIO_Mode_AF;
    GPIO_InitStruct.GPIO_OType=GPIO_OType_PP;
    GPIO_InitStruct.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_InitStruct.GPIO_PuPd=GPIO_PuPd_UP;
    GPIO_Init(GPIOA,&GPIO_InitStruct);

    /*USART basic configuration*/
    USART_InitStruct.USART_BaudRate=BaudRate;
    USART_InitStruct.USART_HardwareFlowControl=USART_HardwareFlowControl_None;
    USART_InitStruct.USART_Mode=USART_Mode_Tx|USART_Mode_Rx;
    USART_InitStruct.USART_Parity=USART_Parity_No;
    USART_InitStruct.USART_StopBits=USART_StopBits_1;
    USART_InitStruct.USART_WordLength=USART_WordLength_8b;
    USART_Init(USART1,&USART_InitStruct);

    /*Enable receive interrupt*/
    NVIC_Config(USART1_IRQn);
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);

    USART_Cmd(USART1,ENABLE);}12345678910111213141516171819202122232425262728293031323334353637383940414243

② USART sends data

void USART1_SendBuf(uint8_t *pBuf, uint32_t u32Len){    while(u32Len--)
    { /*Judge whether the send buffer is empty*/
        while(!USART_GetFlagStatus(USART1,USART_FLAG_TXE));        USART_SendData(USART1,*pBuf++);
    }
}123456789

③USART receives data

uint8_t USART1_ReceiverBuf(void){ /*Judge whether the receive buffer is not empty*/
    while(!USART_GetFlagStatus(USART1,USART_FLAG_RXNE));
    return USART_ReceiveData(USART1);
}123456

3. Remapping of printf function

int fputc(int ch, FILE *f)
{
    USART_SendData(USART1,(uint8_t)ch); while (!USART_GetFlagStatus(USART1, USART_FLAG_TXE)); return (ch);
}123456

5. Summary

When using the printf function of USART, be sure to open the micro library: click the magic wand symbol on the Keil toolbar, enter the Target configuration, and check Use MicroLib