基于STM32移植FreeMODBUS RTU

一、FreeMODBUS

FreeModBus可通过官方网站下载：FreeMODBUS

   包含以下文件

二、FreeMODBUS移植

只需要保留modbus以下内容就可以

还有demo中的port

主要修改port接口中的内容

串口的相关配置内容

/*
 * FreeModbus Libary: BARE Port
 * Copyright (C) 2006 Christian Walter <wolti@sil.at>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * File: $Id$
 */

#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/
#include "mb.h"
#include "mbport.h"
#include "usart.h"

/* ----------------------- static functions ---------------------------------*/
static void prvvUARTTxReadyISR( void );
static void prvvUARTRxISR( void );

/* ----------------------- Start implementation -----------------------------*/
void
vMBPortSerialEnable( BOOL xRxEnable, BOOL xTxEnable ) 
{   //控制中断的使能
    /* If xRXEnable enable serial receive interrupts. If xTxENable enable
     * transmitter empty interrupts.
     */
    if( xRxEnable )
    {   
       //  printf("xRxEnable \n");
        __HAL_UART_ENABLE_IT(&huart2, UART_IT_RXNE);
    }
    else
    {   
        __HAL_UART_DISABLE_IT(&huart2, UART_IT_RXNE);
    }
    if( xTxEnable )
    {   
      //  printf("xTxEnable \n");
        __HAL_UART_ENABLE_IT(&huart2, UART_IT_TXE);
    }
    else
    {   
        __HAL_UART_DISABLE_IT(&huart2, UART_IT_TXE);
    }

}

BOOL
xMBPortSerialInit( UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits, eMBParity eParity )
{
    // MX_USART2_UART_Init(); 在main.c中已经调用 
    return TRUE;
}

BOOL
xMBPortSerialPutByte( CHAR ucByte )
{
    /* Put a byte in the UARTs transmit buffer. This function is called
     * by the protocol stack if pxMBFrameCBTransmitterEmpty( ) has been
     * called. */

    USART2->DR=ucByte;
    return TRUE;
}

BOOL
xMBPortSerialGetByte( CHAR * pucByte )
{
    /* Return the byte in the UARTs receive buffer. This function is called
     * by the protocol stack after pxMBFrameCBByteReceived( ) has been called.
     */
    *pucByte=USART2->DR&0xFF;
    return TRUE;
}

/* Create an interrupt handler for the transmit buffer empty interrupt
 * (or an equivalent) for your target processor. This function should then
 * call pxMBFrameCBTransmitterEmpty( ) which tells the protocol stack that
 * a new character can be sent. The protocol stack will then call 
 * xMBPortSerialPutByte( ) to send the character.
 */
static void prvvUARTTxReadyISR( void )
{
    pxMBFrameCBTransmitterEmpty(  );
}

/* Create an interrupt handler for the receive interrupt for your target
 * processor. This function should then call pxMBFrameCBByteReceived( ). The
 * protocol stack will then call xMBPortSerialGetByte( ) to retrieve the
 * character.
 */
static void prvvUARTRxISR( void ) 
{
    pxMBFrameCBByteReceived(  );
}

void USART2_IRQHandler(void)
{
    // 获得接收中断标志位的时候 调用prvvUARTRxISR
    if(__HAL_UART_GET_FLAG(&huart2, UART_FLAG_RXNE))
    {   
        __HAL_UART_CLEAR_FLAG(&huart2, UART_FLAG_RXNE);
         //printf("rxne \n");
         prvvUARTRxISR();
    }

    // 获得发送中断标志位的时候 调用prvvUARTTxReadyISR
    if(__HAL_UART_GET_FLAG(&huart2, UART_FLAG_TXE))
    {
        __HAL_UART_CLEAR_FLAG(&huart2, UART_FLAG_TXE);
         prvvUARTTxReadyISR();
    }
}

定时器的相关配置

/*
 * FreeModbus Libary: BARE Port
 * Copyright (C) 2006 Christian Walter <wolti@sil.at>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * File: $Id$
 */

/* ----------------------- Platform includes --------------------------------*/
#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/
#include "mb.h"
#include "mbport.h"
#include "tim.h"

/* ----------------------- static functions ---------------------------------*/
static void prvvTIMERExpiredISR( void );

/* ----------------------- Start implementation -----------------------------*/
BOOL
xMBPortTimersInit( USHORT usTim1Timerout50us )
{
    //  MX_TIM3_Init(); main.c已经调用
    return TRUE;
}


inline void
vMBPortTimersEnable(  )
{
    /* Enable the timer with the timeout passed to xMBPortTimersInit( ) */
    __HAL_TIM_SET_COUNTER(&htim3, 0);
    HAL_TIM_Base_Start_IT(&htim3);

}

inline void
vMBPortTimersDisable(  )
{
    /* Disable any pending timers. */
    HAL_TIM_Base_Stop_IT(&htim3);
}

/* Create an ISR which is called whenever the timer has expired. This function
 * must then call pxMBPortCBTimerExpired( ) to notify the protocol stack that
 * the timer has expired.
 */
static void prvvTIMERExpiredISR( void )
{
    ( void )pxMBPortCBTimerExpired(  );
}

/**
  * @brief This function handles TIM3 global interrupt.
  */
void TIM3_IRQHandler(void)
{
    if(__HAL_TIM_GET_FLAG(&htim3,  TIM_FLAG_UPDATE))
    {
      __HAL_TIM_CLEAR_FLAG(&htim3, TIM_FLAG_UPDATE);
        prvvTIMERExpiredISR();
    }
}

port.c中是关于线圈，离散寄存器，保持寄存器，输入寄存器相关操作方法的实现内容，且声明了相关寄存器的缓存区。

关闭ASCII

初始化

三、记录一下

   使用Modbus Poll通过modbus读取设备上的信息，Modbus Poll会设置slaveId所以在它日志文件中没有地址ID，设备接收到的数据是没问题的

关于收发命令的含义

接收命令 (Rx): 01 03 00 00 00 0A C5 CD

Modbus RTU 请求帧，用于读取保持寄存器：

• 从站 ID: 01 - 目标设备地址为 1
• 功能码: 03 - 表示读取保持寄存器（Read Holding Registers）
• 起始地址: 00 00 - 从地址 0 开始读取（对应 Modbus 地址 40001）
• 寄存器数量: 00 0A - 读取 10 个寄存器（0x0A = 10）
• CRC校验: C5 CD - 循环冗余校验码

发送命令 (Tx): 01 03 14 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 A3 67

Modbus RTU 响应帧，服务器对请求的回复：

• 从站 ID: 01 - 响应来自设备地址 1
• 功能码: 03 - 与请求的功能码相同，表示正常响应
• 数据长度: 14 - 后面有 20 字节的数据（10 个寄存器 × 2 字节/寄存器）
• 寄存器数据: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 10 个寄存器的值都是 0
• CRC校验: A3 67 - 响应帧的校验码

数据解析

根据项目配置，这些寄存器对应以下变量：

• 地址 40001: REG_HOLD_BUF[0]
• 地址 40002: REG_HOLD_BUF[1]
• ...
• 地址 40010: REG_HOLD_BUF[9]

发送的请求是读取地址 40001 开始的 10 个保持寄存器。服务器返回了这 10 个寄存器的值，全部为 0。

通信流程

1. 主机发送请求：01 03 00 00 00 0A C5 CD
2. 从机接收并处理请求
3. 从机返回响应：01 03 14 00 00 ... A3 67

如果需要修改这些寄存器的值，可以使用功能码 6（写单个寄存器）或 16（写多个寄存器）。

Modbus Poll也有其他的命令，可以自行尝试一下