【国民技术N32项目移植】开源库FreeModbus移植

简介

Modbus是一种串行通信协议，是Modicon公司（现在的施耐德电气 Schneider Electric）于1979年为使用可编程逻辑控制器（PLC）通信而发表。

Modbus已经成为工业领域通信协议的业界标准（De facto），并且现在是工业电子设备之间常用的连接方式。

Modbus通信协议是一种主从的协议，在一个Modbus网络里面只能有一个主机，但是可以有多个从机，从机与从机之间通过地址进行区分，每个从机都具有唯一的设备地址。

每次通讯必须由主机进行发起，从机进行响应。

本次基于开发板的485硬件接口移植Modbus开源协议栈FreeModbus实现Modbus从机。

（FreeModbus目前只能支持从机）

涉及的硬件资源

1、USART
2、timer

USART驱动

使用USART3作为modbus的串口。
配置为发送使能，接收使能，接收中断，发送完成中断，9600bps波特率，8N1。

配置代码：

/**************************************************************************
USART3 Modbus串口配置
***************************************************************************/
//配置usart的中断优先级
static void NVIC_Configuration_Usart_Modbus(void);
//配置usart的GPIO
static void GPIO_Configuration_Usart_Modbus(void);
//usart 通讯参数设置
void usart_modbus_com_config(void);

//usart 初始化
void usart_modbus_init(void)
{
    /* Enable GPIO clock */
    RCC_EnableAPB2PeriphClk(USART_MODBUS_GPIO_CLK | RCC_APB2_PERIPH_AFIO, ENABLE);
    /* Enable USART Clock */
    USART_MODBUS_APBxClkCmd(USART_MODBUS_CLK, ENABLE);

    //设置中断优先级
    NVIC_Configuration_Usart_Modbus();
    //配置debug usart的引脚
    GPIO_Configuration_Usart_Modbus();
    //usart 通讯参数设置
    usart_modbus_com_config();

}

//配置usart的中断优先级
static void NVIC_Configuration_Usart_Modbus(void)
{
    NVIC_InitType NVIC_InitStructure;

    /* Configure the NVIC Preemption Priority Bits */
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);

    /* Enable the USART Interrupt */
    NVIC_InitStructure.NVIC_IRQChannel            = USART_MODBUS_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd         = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

}

//配置usart的GPIO
static void GPIO_Configuration_Usart_Modbus(void)
{
    GPIO_InitType GPIO_InitStructure;

    /* Configure USART Rx as input floating */
    GPIO_InitStructure.Pin       = USART_MODBUS_RxPin;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitPeripheral(USART_MODBUS_GPIO, &GPIO_InitStructure);

    /* Configure USART Tx as alternate function push-pull */
    GPIO_InitStructure.Pin        = USART_MODBUS_TxPin;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_PP;
    GPIO_InitPeripheral(USART_MODBUS_GPIO, &GPIO_InitStructure);
}

//usart 通讯参数设置
void usart_modbus_com_config(void)
{
    USART_InitType USART_InitStructure;
    /* Debug USART configuration ------------------------------------------------------*/
    USART_InitStructure.BaudRate            = 9600;
    USART_InitStructure.WordLength          = USART_WL_8B;
    USART_InitStructure.StopBits            = USART_STPB_1;
    USART_InitStructure.Parity              = USART_PE_NO;
    USART_InitStructure.HardwareFlowControl = USART_HFCTRL_NONE;
    USART_InitStructure.Mode                = USART_MODE_RX | USART_MODE_TX;

    /* Configure USART */
    USART_Init(USART_MODBUS, &USART_InitStructure);
    
    //清接收中断标志
	USART_ClrIntPendingBit(USART_MODBUS, USART_INT_RXDNE);
	USART_ClrFlag(USART_MODBUS, USART_FLAG_RXDNE);
    /* Enable USART Receive interrupts */
    USART_ConfigInt(USART_MODBUS, USART_INT_RXDNE, ENABLE);
	
    //清发送中断标志
	USART_ClrIntPendingBit(USART_MODBUS, USART_INT_TXC); 
	USART_ClrFlag(USART_MODBUS, USART_FLAG_TXC);
    /* Enable USART Transmit interrupts */
    USART_ConfigInt(USART_MODBUS, USART_INT_TXC, ENABLE);

    /* Enable the USART */
    USART_Enable(USART_MODBUS, ENABLE);
	  
}

//输出字符串
void modbus_put_str(uint8_t *str)
{
    while(*str != '\0')
    {
        while(USART_GetFlagStatus(USART_MODBUS, USART_FLAG_TXDE) == RESET);
        /* Write one byte to the transmit data register */
        USART_SendData(USART_MODBUS, *str); 
        str++;  
    }
}

//接收中断使能/失能
void modbus_rx_int_config(uint8_t enable)
{
    /* Enable/Disable USART Receive interrupts */
    USART_ConfigInt(USART_MODBUS, USART_INT_RXDNE, enable);    
}

//接收中断使能/失能
void modbus_tx_int_config(uint8_t enable)
{
    /* Enable/Disable USART transmit interrupts */
    USART_ConfigInt(USART_DEBUG, USART_INT_TXDE, enable);   
}

Timer驱动

FreeModbus需要用到一个50us时基的定时器，所以这里先将timer的驱动编写好，并测试成功。

timer驱动配置：

时基50us，带有输入参数，参数表示50us的n倍，也就是参数为1表示定时50us，参数为2表示2*50us，以此类推。

配置代码如下：

#include "timer.h"

//timer1配置
void TIM1_config(uint16_t n_us_50)
{
    TIM_TimeBaseInitType TIM_TimeBaseStructure;

    /* TIM1 clock enable */
    RCC_EnableAPB2PeriphClk(RCC_APB2_PERIPH_TIM1, ENABLE);

    /* Time base configuration */
    TIM_TimeBaseStructure.Period    = 36 * n_us_50 * 50;
    TIM_TimeBaseStructure.Prescaler = 3;
    TIM_TimeBaseStructure.ClkDiv    = 0;
    TIM_TimeBaseStructure.CntMode   = TIM_CNT_MODE_UP;

    TIM_InitTimeBase(TIM1, &TIM_TimeBaseStructure);

    /* Prescaler configuration */
    TIM_ConfigPrescaler(TIM1, 3, TIM_PSC_RELOAD_MODE_IMMEDIATE);

    /* TIM1 enable update irq */
    TIM_ConfigInt(TIM1, TIM_INT_UPDATE, ENABLE);

    /* TIM1 enable counter */
    TIM_Enable(TIM1, ENABLE);
}

//NVIC配置
void NVIC_Config_timer1(void)
{
    NVIC_InitType NVIC_InitStructure;
	
    /* Enable the TIM1 global Interrupt */
    NVIC_InitStructure.NVIC_IRQChannel                   = TIM1_UP_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority        = 1;
    NVIC_InitStructure.NVIC_IRQChannelCmd                = ENABLE;

    NVIC_Init(&NVIC_InitStructure);
}

//timer1初始化
void timer1_init(void)
{
    NVIC_Config_timer1();  
    TIM1_config(20);         //1ms中断一次
}

//timer1初始化
void timer1_init_for_modbus(uint16_t us_50)
{
    NVIC_Config_timer1();
    TIM1_config(us_50);
}

FreeModbus库驱动对接

重点来了，这是本篇最核心的东西。

1、下载FreeModbus源码

源码下载地址：https://www.embedded-experts.at/en/freemodbus-downloads/

2、将源码加入工程

源码解压后，得到如下文件和文件夹：

我们需要的是modbus这个文件夹，和demo->BARE下的port文件夹。

将这个两个文件夹添加到工程中：

添加头文件路径“

3、修改portserial.c文件

portserial.c文件主要是对UART驱动的对接，需要对接的函数主要有4个。

① void vMBPortSerialEnable( BOOL xRxEnable, BOOL xTxEnable )

用于对串口发送和接收进行使能或者失能

② BOOL xMBPortSerialInit( UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits, eMBParity eParity )

用于对485进行初始化

③BOOLxMBPortSerialPutByte( CHAR ucByte )

用于485发送一个字节

④BOOLxMBPortSerialGetByte( CHAR * pucByte )

用于485读取一个字节

另外，我将uart的回调函数也是放在这个文件中。

对接后完整portserial.c文件如下：

/*
 * 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"
#include "uart.h"

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

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

/* ----------------------- Start implementation -----------------------------*/
void
vMBPortSerialEnable( BOOL xRxEnable, BOOL xTxEnable )
{
    /* If xRXEnable enable serial receive interrupts. If xTxENable enable
     * transmitter empty interrupts.
     */
    if (xRxEnable == TRUE)
    {
        modbus_rx_state = 0;
    }
    else
    {
        modbus_rx_state = 1;
    }

    if (xTxEnable == TRUE)
    {
        modbus_tx_state = 0;
    }
    else
    {
        modbus_tx_state = 1;
    }  
}

BOOL
xMBPortSerialInit( UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits, eMBParity eParity )
{
    usart_modbus_init();
    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. */
    USART_SendData(USART_MODBUS, 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 = modbus_rx_char;
    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(  );
}


/**
 * [url=home.php?mod=space&uid=2666770]@Brief[/url]  This function handles USARTy global interrupt request.
 */
void USART_MODBUS_IRQHandler(void)
{
    if (USART_GetIntStatus(USART_MODBUS, USART_INT_RXDNE) != RESET)
    {
        /* Read one byte from the receive data register */
        if (modbus_rx_state == 0)
        {
            modbus_rx_char = USART_ReceiveData(USART_MODBUS);
            prvvUARTRxISR();
        }
        else
        {
            USART_ReceiveData(USART_MODBUS);
        }
        //清接收中断标志
        USART_ClrIntPendingBit(USART_MODBUS, USART_INT_RXDNE); 
		USART_ClrFlag(USART_MODBUS, USART_FLAG_RXDNE);
    }

    if (USART_GetIntStatus(USART_MODBUS, USART_INT_TXC) != RESET)
    {
        /* Write one byte to the transmit data register */
        if (modbus_tx_state == 0)
        {
            prvvUARTTxReadyISR();
        }
        //清发送中断标志
        USART_ClrIntPendingBit(USART_MODBUS, USART_INT_TXC); 
        USART_ClrFlag(USART_MODBUS, USART_FLAG_TXDE);
    }
}

4、修改porttimer.c文件

该文件需要对接3个函数。

① BOOL xMBPortTimersInit( USHORT usTim1Timerout50us )

用于对timer进行初始化

② void vMBPortTimersEnable( )

用于使能timer，让timer开始计数

③ void vMBPortTimersDisable( )

用于失能timer，让timer停止计数

另外，timer中断的回调函数也是放在这个文件中。

对接后完整porttimer.c文件如下：

/*
 * 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 "timer.h"
#include "led.h"
#include <stdio.h>
/* ----------------------- static functions ---------------------------------*/
static void prvvTIMERExpiredISR( void );

/* ----------------------- Start implementation -----------------------------*/
BOOL
xMBPortTimersInit( USHORT usTim1Timerout50us )
{
    /* Initializes the module. */
    timer1_init_for_modbus(usTim1Timerout50us);
    return TRUE;
}


void
vMBPortTimersEnable(  )
{
    /* Enable the timer with the timeout passed to xMBPortTimersInit( ) */
    /* Read the current counter value. Counter value is in status.counter. */
    
    TIM_SetCnt(TIM1, 0);
    /* TIM1 enable counter */
    TIM_Enable(TIM1, ENABLE);
}

void
vMBPortTimersDisable(  )
{
    /* Read the current counter value. Counter value is in status.counter. */
    /* TIM1 disable counter */
    TIM_Enable(TIM1, DISABLE);   
}

/* 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(  );
}


uint16_t timer_int_cnt = 0;

/**
 * @brief  This function handles TIM1 update interrupt request.
 */
void TIM1_UP_IRQHandler(void)
{
    if (TIM_GetIntStatus(TIM1, TIM_INT_UPDATE) != RESET)
    {
        TIM_ClrIntPendingBit(TIM1, TIM_INT_UPDATE);

        prvvTIMERExpiredISR();
        timer_int_cnt++;
        if(timer_int_cnt > 1000)
        {
            LedBlink(LED1_PORT, LED1_PIN);
            timer_int_cnt = 0;
        }

    }
}

5、定义Modbus寄存器并实现读写函数

我将寄存器定义和读写函数的实现放在了自己定义的modbus_read_write.c文件中，完整代码如下：

注意：这个几个函数必须实现，否则会报错

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

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

/* ----------------------- Defines ------------------------------------------*/
#define REG_INPUT_START   1000
#define REG_INPUT_NREGS   4
#define REG_HOLDING_START 1000
#define REG_HOLDING_NREGS 130

/* ----------------------- Static variables ---------------------------------*/
static USHORT   usRegInputStart = REG_INPUT_START;
static USHORT   usRegInputBuf[REG_INPUT_NREGS] = {1,2,3,4};
static USHORT   usRegHoldingStart = REG_HOLDING_START;
static USHORT   usRegHoldingBuf[REG_HOLDING_NREGS] = {10,11,12,13};

/* ----------------------- Start implementation -----------------------------*/

void free_modbus_init(eMBMode eMode, UCHAR ucSlaveAddress, UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity)
{
    eMBInit( eMode, ucSlaveAddress, ucPort, ulBaudRate, eParity );
    eMBEnable();
}

eMBErrorCode
eMBRegInputCB( UCHAR * pucRegBuffer, USHORT usAddress, USHORT usNRegs )
{
    eMBErrorCode    eStatus = MB_ENOERR;
    int             iRegIndex;

    if( ( usAddress >= REG_INPUT_START )
        && ( usAddress + usNRegs <= REG_INPUT_START + REG_INPUT_NREGS ) )
    {
        iRegIndex = ( int )( usAddress - usRegInputStart );
        while( usNRegs > 0 )
        {
            *pucRegBuffer++ = ( unsigned char )( usRegInputBuf[iRegIndex] >> 8 );
            *pucRegBuffer++ = ( unsigned char )( usRegInputBuf[iRegIndex] & 0xFF );
            iRegIndex++;
            usNRegs--;
        }
    }
    else
    {
        eStatus = MB_ENOREG;
    }

    return eStatus;
}

eMBErrorCode
eMBRegHoldingCB( UCHAR * pucRegBuffer, USHORT usAddress, USHORT usNRegs, eMBRegisterMode eMode )
{
    eMBErrorCode    eStatus = MB_ENOERR;
    int             iRegIndex;

    if( ( usAddress >= REG_HOLDING_START ) &&
        ( usAddress + usNRegs <= REG_HOLDING_START + REG_HOLDING_NREGS ) )
    {
        iRegIndex = ( int )( usAddress - usRegHoldingStart );
        switch ( eMode )
        {
            /* Pass current register values to the protocol stack. */
        case MB_REG_READ:
            while( usNRegs > 0 )
            {
                *pucRegBuffer++ = ( unsigned char )( usRegHoldingBuf[iRegIndex] >> 8 );
                *pucRegBuffer++ = ( unsigned char )( usRegHoldingBuf[iRegIndex] & 0xFF );
                iRegIndex++;
                usNRegs--;
            }
            break;

            /* Update current register values with new values from the
             * protocol stack. */
        case MB_REG_WRITE:
            while( usNRegs > 0 )
            {
                usRegHoldingBuf[iRegIndex] = *pucRegBuffer++ << 8;
                usRegHoldingBuf[iRegIndex] |= *pucRegBuffer++;
                iRegIndex++;
                usNRegs--;
            }
        }
    }
    else
    {
        eStatus = MB_ENOREG;
    }
    return eStatus;
}

eMBErrorCode
eMBRegCoilsCB( UCHAR * pucRegBuffer, USHORT usAddress, USHORT usNCoils, eMBRegisterMode eMode )
{
    return MB_ENOREG;
}

eMBErrorCode
eMBRegDiscreteCB( UCHAR * pucRegBuffer, USHORT usAddress, USHORT usNDiscrete )
{
    return MB_ENOREG;
}

6、修改main.c文件

在main()函数中加入Modbus初始化相关内容和状态轮询函数，完整内容如下：

/*****************************************************************************
 * Copyright (c) 2019, Nations Technologies Inc.
 *
 * All rights reserved.
 * ****************************************************************************
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the disclaimer below.
 *
 * Nations' name may not be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY NATIONS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * DISCLAIMED. IN NO EVENT SHALL NATIONS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * ****************************************************************************/

/**
 * [url=home.php?mod=space&uid=1455510]@file[/url] main.c
 * [url=home.php?mod=space&uid=40524]@author[/url] Nations
 * [url=home.php?mod=space&uid=644434]@version[/url] v1.0.0
 *
 * [url=home.php?mod=space&uid=855824]@copyright[/url] Copyright (c) 2019, Nations Technologies Inc. All rights reserved.
 */
#include "main.h"
#include <stdio.h>
#include <stdint.h>
#include "led.h"
#include "clock.h"
#include "uart.h"
#include "timer.h"
#include "modbus_read_write.h"
#include "can.h"
/**
 * @brief  Inserts a delay time.
 * [url=home.php?mod=space&uid=3142012]@param[/url] count specifies the delay time length.
 */
void Delay(uint32_t count)
{
    for (; count > 0; count--)
        ;
}

/**
 * @brief  Main program.
 */
int main(void)
{
    /*SystemInit() function has been called by startup file startup_n32g45x.s*/
    clock_init();
    /* Initialize Led1~Led5 as output pushpull mode*/
    LedInit(LED1_PORT, LED1_PIN);
    LedInit(LED2_PORT, LED2_PIN);
    LedInit(LED3_PORT, LED3_PIN);

    LedOff(LED3_PORT, LED3_PIN);

    //usart_debug_init();
        /* 初始化Modbus端口和状态 */
    free_modbus_init(MB_RTU, 1, 5, 9600, MB_PAR_NONE);
    //usart_modbus_init();
    //timer1_init();

    Tx_Frame_Message_Init();
    /* Configures CAN IOs */
    CAN_GPIO_init();
    /* Configures CAN */
    CAN_init();

    CAN_Tx_Process();
    while (1)
    {
                /* 状态机轮询 */
        ( void )eMBPoll();
        CAN_Recieve_Process();
        //printf((const char *)"N32G45x\r\n");
			  //put_str((uint8_t *)"modbus test...\r\n");
        //modbus_put_str((uint8_t *)"modbus test...\r\n");	
        /* Insert delay */
        //Delay(0x28FFFF);
    }
}

/**
 * @brief Assert failed function by user.
 * @param file The name of the call that failed.
 * @param line The source line number of the call that failed.
 */
#ifdef USE_FULL_ASSERT
void assert_failed(const uint8_t* expr, const uint8_t* file, uint32_t line)
{
    while (1)
    {
    }
}
#endif // USE_FULL_ASSERT

/**
 * @}
 */

7、修改mbrtu.c文件

修改mbrtu.c中eMBRTUSend函数，如果不修改无法触发485发送。

8、修改mbconfig.h文件

取消对ASCII的支持

9、去掉寄存器地址自动加一

需要修改四个文件，分别为mbfunccoils.c、mbfuncdisc.c、mbfuncholding.c、mbfuncinput.c

直接去对应的文件搜索：usRegAddress++;

然后屏蔽掉。

mbfunccoils.c里面有三处

mbfuncdisc.c里面有一处

mbfuncholding.c里面有三处

mbfuncinput.c里面有一处

如果不修改，绝对不能正常工作。

测试

编译下载运行，并使用PC端工具Modbus Poll模拟Modbus主机来进行测试。

如下：

经过测试，实测开发板能正确与Modbus Poll相互通讯。

至此，FreeModbus开源库移植成功/