在stm32中用串口代码写modbus协议

下面是一个简单的示例代码，用于在STM32中使用串口实现Modbus协议：

#include "stm32f10x.h"
#include "modbus.h"

#define MODBUS_SLAVE_ADDRESS    0x01

// 串口发送字节
void USART_SendByte(uint8_t byte) {
    while (!(USART1->SR & USART_SR_TXE));
    USART1->DR = byte;
}

// 串口接收字节
uint8_t USART_ReceiveByte() {
    while (!(USART1->SR & USART_SR_RXNE));
    return USART1->DR;
}

// 初始化串口
void USART_Init() {
    // 配置GPIO
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // 配置串口
    USART_InitTypeDef USART_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    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(USART1, &USART_InitStructure);
    USART_Cmd(USART1, ENABLE);
}

int main() {
    // 初始化串口
    USART_Init();

    // 初始化Modbus
    modbus_init(MODBUS_SLAVE_ADDRESS);

    // 循环处理Modbus请求
    while (1) {
        // 接收请求
        uint8_t request[MODBUS_MAX_MESSAGE_LENGTH];
        uint8_t request_length = 0;
        while (1) {
            uint8_t byte = USART_ReceiveByte();
            request[request_length++] = byte;
            if (request_length >= MODBUS_MAX_MESSAGE_LENGTH) {
                break;
            }
            if (byte == '\n') {
                break;
            }
        }

        // 处理请求
        uint8_t response[MODBUS_MAX_MESSAGE_LENGTH];
        uint8_t response_length = modbus_process(request, request_length, response);

        // 发送响应
        for (int i = 0; i < response_length; i++) {
            USART_SendByte(response[i]);
        }
    }
}

在上述示例代码中，我们通过 `USART_SendByte` 和 `USART_ReceiveByte` 函数来实现通过串口发送和接收字节的功能。我们还通过 `modbus_init` 函数来初始化Modbus协议，然后在一个无限循环中不断接收Modbus请求，处理请求并发送响应。需要注意的是，此处仅为示例代码，具体的Modbus处理函数需要根据自己的需求进行编写。