串口功能学习和例程演示

CH32V208芯片支持串口通讯，查看数据手册可知，其有3个串口。

官方的参考手册中对USART的功能进行了详细的介绍

在官方提供的演示例程中，提供了串口的多种功能演示例程。

本次对其中的DMA、Interrupt以及Printf功能进行测试和学习。使用MounRiver Studio的导入功能，将相应的工程导入到工作空间中。

导入后的效果如下所示

USART_Printf功能演示

通过串口打印数据是嵌入式开发中必备的一项功能，在导入的USART_Printf工程下可以看到与串口打印数据相关的源代码。

相关的代码如下

#ifndef __DEBUG_H
#define __DEBUG_H

#include "stdio.h"
#include "ch32v20x.h"

#ifdef __cplusplus
extern "C" {
#endif

/* UART Printf Definition */
#define DEBUG_UART1    1
#define DEBUG_UART2    2
#define DEBUG_UART3    3

/* DEBUG UATR Definition */
#ifndef DEBUG
#define DEBUG   DEBUG_UART1
#endif

void USART_Printf_Init(uint32_t baudrate);

#if(DEBUG)
  #define PRINT(format, ...)    printf(format, ##__VA_ARGS__)
#else
  #define PRINT(X...)
#endif

#ifdef __cplusplus
}
#endif

#endif

/*********************************************************************
 * @fn      USART_Printf_Init
 *
 * @brief   Initializes the USARTx peripheral.
 *
 * @param   baudrate - USART communication baud rate.
 *
 * @return  None
 */
void USART_Printf_Init(uint32_t baudrate)
{
    GPIO_InitTypeDef  GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;

#if(DEBUG == DEBUG_UART1)
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

#elif(DEBUG == DEBUG_UART2)
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

#elif(DEBUG == DEBUG_UART3)
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

#endif

    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_Tx;

#if(DEBUG == DEBUG_UART1)
    USART_Init(USART1, &USART_InitStructure);
    USART_Cmd(USART1, ENABLE);

#elif(DEBUG == DEBUG_UART2)
    USART_Init(USART2, &USART_InitStructure);
    USART_Cmd(USART2, ENABLE);

#elif(DEBUG == DEBUG_UART3)
    USART_Init(USART3, &USART_InitStructure);
    USART_Cmd(USART3, ENABLE);

#endif
}

/*********************************************************************
 * @fn      _write
 *
 * @brief   Support Printf Function
 *
 * @param   *buf - UART send Data.
 *          size - Data length
 *
 * @return  size: Data length
 */
__attribute__((used))
int _write(int fd, char *buf, int size)
{
    int i;

    for(i = 0; i < size; i++){
#if(DEBUG == DEBUG_UART1)
        while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
        USART_SendData(USART1, *buf++);
#elif(DEBUG == DEBUG_UART2)
        while(USART_GetFlagStatus(USART2, USART_FLAG_TC) == RESET);
        USART_SendData(USART2, *buf++);
#elif(DEBUG == DEBUG_UART3)
        while(USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET);
        USART_SendData(USART3, *buf++);
#endif
    }

    return size;
}

程序的演示效果如下

USART_Interrupt功能演示

配合USART的中断实现收发功能，实现实时地收发数据，同时可以减小CPU的使用率。示例程序中演示了使用串口地TXE和RXNE中断实现数据的收发。

程序硬件上使用USART2和USART3作为收发的硬件，两个串口都开启中断功能。主程序中初始化硬件，并配置相关外设的功能后，USART3发送数据并通过检查TXE中断标志位和计数变量确定数据是否发送完毕，同时USART2开始了接收中断，在中断函数中进行数据接收和计数处理；接下来USART2和USART3互换位置，进行数据的收发。数据接收完毕后，对缓存区中的数据进行对比，确定数据是否完整地实现了传输。

串口配置和中断检测函数

/*********************************************************************
 * @fn      USARTx_CFG
 *
 * @brief   Initializes the USART2 & USART3 peripheral.
 *
 * @return  none
 */
void USARTx_CFG(void)
{
    GPIO_InitTypeDef  GPIO_InitStructure = {0};
    USART_InitTypeDef USART_InitStructure = {0};
    NVIC_InitTypeDef  NVIC_InitStructure = {0};

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2 | RCC_APB1Periph_USART3, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB, ENABLE);

    /* USART2 TX-->A.2   RX-->A.3 */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    /* USART3 TX-->B.10  RX-->B.11 */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    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_Tx | USART_Mode_Rx;

    USART_Init(USART2, &USART_InitStructure);
    USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);

    USART_Init(USART3, &USART_InitStructure);
    USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);

    NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    USART_Cmd(USART2, ENABLE);
    USART_Cmd(USART3, ENABLE);
}

发送中断检测代码如下：

while(TxCnt2 < TxSize2) /* USART3--->USART2 */
    {
        USART_SendData(USART3, TxBuffer2[TxCnt2++]);
        while(USART_GetFlagStatus(USART3, USART_FLAG_TXE) == RESET) /* waiting for sending finish */
        {
        }
    }
    while(TxCnt1 < TxSize1) /* USART2--->USART3 */
    {
        USART_SendData(USART2, TxBuffer1[TxCnt1++]);
        while(USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET) /* waiting for sending finish */
        {
        }
    }

接收数据中检测函数

/*********************************************************************
 * @fn      USART2_IRQHandler
 *
 * @brief   This function handles USART2 global interrupt request.
 *
 * @return  none
 */
void USART2_IRQHandler(void)
{
    if(USART_GetITStatus(USART2, USART_IT_RXNE) != RESET)
    {
        RxBuffer1[RxCnt1++] = USART_ReceiveData(USART2);

        if(RxCnt1 == TxSize2)
        {
            USART_ITConfig(USART2, USART_IT_RXNE, DISABLE);
            Rxfinish1 = 1;
        }
    }
}

/*********************************************************************
 * @fn      USART3_IRQHandler
 *
 * @brief   This function handles USART3 global interrupt request.
 *
 * @return  none
 */
void USART3_IRQHandler(void)
{
    if(USART_GetITStatus(USART3, USART_IT_RXNE) != RESET)
    {
        RxBuffer2[RxCnt2++] = USART_ReceiveData(USART3);

        if(RxCnt2 == TxSize1)
        {
            USART_ITConfig(USART3, USART_IT_RXNE, DISABLE);
            Rxfinish2 = 1;
        }
    }
}

USART_DMA功能演示

借助DMA配合USART可以实现大量数据地传输的同时减少CPU的使用率。在官方提供的示例程序中，配置了USART2和USART3的参数和DMA通道参数。随后，使用DMA的数据传输，并在主循环中对DMA传输的状态位进行检测，当检测到所有的DMA传输完毕后，对缓存区内的数据进行对比，并置位相应的状态位。通过调试串口向上位机发送调试数据。

DMA配置函数如下：

/*********************************************************************
 * @fn      DMA_INIT
 *
 * @brief   Configures the DMA for USART2 & USART3.
 *
 * @return  none
 */
void DMA_INIT(void)
{
    DMA_InitTypeDef DMA_InitStructure = {0};
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

    DMA_DeInit(DMA1_Channel7);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART2->DATAR); /* USART2->DATAR:0x40004404 */
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)TxBuffer1;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = TxSize1;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel7, &DMA_InitStructure);

    DMA_DeInit(DMA1_Channel6);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART2->DATAR);
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)RxBuffer1;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = TxSize2;
    DMA_Init(DMA1_Channel6, &DMA_InitStructure);

    DMA_DeInit(DMA1_Channel2);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART3->DATAR); /* USART2->DATAR:0x40004804 */
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)TxBuffer2;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = TxSize2;
    DMA_Init(DMA1_Channel2, &DMA_InitStructure);

    DMA_DeInit(DMA1_Channel3);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART3->DATAR);
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)RxBuffer2;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = TxSize1;
    DMA_Init(DMA1_Channel3, &DMA_InitStructure);
}

主函数中DMA启动以及传输完成判断标志位检测

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
    Delay_Init();
    USART_Printf_Init(115200);
    printf("SystemClk:%d\r\n", SystemCoreClock);

    printf("USART DMA TEST\r\n");
    DMA_INIT();
    USARTx_CFG(); /* USART2 & USART3 INIT */
    USART_DMACmd(USART2, USART_DMAReq_Tx | USART_DMAReq_Rx, ENABLE);
    USART_DMACmd(USART3, USART_DMAReq_Rx | USART_DMAReq_Tx, ENABLE);
    while(DMA_GetFlagStatus(DMA1_FLAG_TC7) == RESET) /* Wait until USART2 TX DMA1 Transfer Complete */
    {
    }
    while(DMA_GetFlagStatus(DMA1_FLAG_TC6) == RESET) /* Wait until USART2 RX DMA1 Transfer Complete */
    {
    }
    while(DMA_GetFlagStatus(DMA1_FLAG_TC2) == RESET) /* Wait until USART3 TX DMA1 Transfer Complete */
    {
    }
    while(DMA_GetFlagStatus(DMA1_FLAG_TC3) == RESET) /* Wait until USART3 RX DMA1 Transfer Complete */
    {
    }

运行的输出结果如图所示：