本帖最后由 hbzjt2011 于 2025-8-2 14:11 编辑
1. 概述 本文将介绍如何在Geehy APM32F402R Micro-EVB开发板上，基于RT-Thread实时操作系统和Freemodbus开源库实现Modbus主机功能，并使用Modbus Slave工具进行通信测试。
1.1 硬件平台- 开发板: Geehy APM32F402R Micro-EVB
- MCU: APM32F402RBT6 (Cortex-M4F, 128KB Flash, 32KB SRAM)
- 通信接口: UART2
1.2 软件环境- 操作系统: RT-Thread 5.2.1
- Modbus库: Freemodbus 1.6
- 开发环境: Keil MDK
- 测试工具: Modbus Slave
1.3 FreeModbus 简介FreeModbus 是一个基于 BSD 协议的开源嵌入式 Modbus 协议栈，支持 RTU、ASCII 及 TCP 三种传输模式，具有高度可移植性和模块化设计。它可运行于裸机系统，也适用于集成 RTOS 的嵌入式平台，特别适合 STM32、AVR、ARM Cortex-M 等微控制器平台。FreeModbus 提供从站和主站功能接口，便于快速集成至工业控制、自动化设备中。我们将采用 RTU 从站模式与主机进行通信，结合 UART 作为物理接口。 标准Modbus功能: - 支持保持寄存器读写（功能码03/06/16）
- 支持输入寄存器读取（功能码04）
- 支持线圈读写（功能码01/05/15）
- 支持离散输入读取（功能码02）
系统架构
应用层 (user_mb_app.c)
↓
Modbus协议栈 (mb.c, mbrtu.c等)
↓
移植层 (mb_port_*.c)
↓
ThreadX RTOS
↓
APM32F402硬件层
2. 环境搭建2.1 RT-Thread配置在RT-Thread配置中启用以下组件：
RT-Thread Components → Device Drivers → Using Serial Device Drivers
RT-Thread Components → Device Drivers → Using Pin Device Drivers
RT-Thread online packages → IoT - internet of things → freemodbus
2.2 Freemodbus软件包配置在RT-Thread配置菜单中设置： 使用pkgs --update更新组件 使用scons --target=mdk5更新工程
3. 软件实现
生成的Keil工程如下：
board.c
/*
* Copyright (c) 2006-2022, RT-Thread Development Team
*
* SPDX-License-Identifier: Apache-2.0
*
* Change Logs:
* Date Author Notes
* 2025-08-04 Abbcc first version
*/
#include "board.h"
void apm32_usart_init(void)
{
GPIO_Config_T GPIO_ConfigStruct = {0U};
#ifdef BSP_USING_UART1
RCM_EnableAPB2PeriphClock(RCM_APB2_PERIPH_GPIOA);
RCM_EnableAPB2PeriphClock(RCM_APB2_PERIPH_USART1);
GPIO_ConfigStruct.mode = GPIO_MODE_AF_PP;
GPIO_ConfigStruct.pin = GPIO_PIN_9;
GPIO_ConfigStruct.speed = GPIO_SPEED_50MHz;
GPIO_Config(GPIOA, &GPIO_ConfigStruct);
GPIO_ConfigStruct.mode = GPIO_MODE_IN_FLOATING;
GPIO_ConfigStruct.pin = GPIO_PIN_10;
GPIO_ConfigStruct.speed = GPIO_SPEED_50MHz;
GPIO_Config(GPIOA, &GPIO_ConfigStruct);
#endif
#ifdef BSP_USING_UART2
RCM_EnableAPB2PeriphClock(RCM_APB2_PERIPH_GPIOA);
RCM_EnableAPB1PeriphClock(RCM_APB1_PERIPH_USART2);
GPIO_ConfigStruct.mode = GPIO_MODE_AF_PP;
GPIO_ConfigStruct.pin = GPIO_PIN_2;
GPIO_ConfigStruct.speed = GPIO_SPEED_50MHz;
GPIO_Config(GPIOA, &GPIO_ConfigStruct);
GPIO_ConfigStruct.mode = GPIO_MODE_IN_FLOATING;
GPIO_ConfigStruct.pin = GPIO_PIN_3;
GPIO_ConfigStruct.speed = GPIO_SPEED_50MHz;
GPIO_Config(GPIOA, &GPIO_ConfigStruct);
#endif
}
void apm32_msp_can_init(void *Instance)
{
#if defined(BSP_USING_CAN1) || defined(BSP_USING_CAN2)
GPIO_Config_T GPIO_InitStructure;
CAN_T *CANx = (CAN_T *)Instance;
if (CAN1 == CANx)
{
RCM_EnableAPB1PeriphClock(RCM_APB1_PERIPH_CAN1);
RCM_EnableAHB1PeriphClock(RCM_AHB1_PERIPH_GPIOB);
/* PB8: CAN1_RX, PB9: CAN1_TX */
GPIO_InitStructure.pin = GPIO_PIN_8 | GPIO_PIN_9;
GPIO_InitStructure.mode = GPIO_MODE_AF;
GPIO_InitStructure.otype = GPIO_OTYPE_PP;
GPIO_InitStructure.speed = GPIO_SPEED_100MHz;
GPIO_InitStructure.pupd = GPIO_PUPD_UP;
GPIO_Config(GPIOB, &GPIO_InitStructure);
GPIO_ConfigPinAF(GPIOB, GPIO_PIN_SOURCE_8, GPIO_AF_CAN1);
GPIO_ConfigPinAF(GPIOB, GPIO_PIN_SOURCE_9, GPIO_AF_CAN1);
}
else if (CAN2 == CANx)
{
/* When using the CAN2 peripheral, the CAN1 clock must be turned on */
RCM_EnableAPB1PeriphClock(RCM_APB1_PERIPH_CAN1);
RCM_EnableAPB1PeriphClock(RCM_APB1_PERIPH_CAN2);
RCM_EnableAHB1PeriphClock(RCM_AHB1_PERIPH_GPIOB);
/* PB12: CAN2_RX, PB13: CAN2_TX */
GPIO_InitStructure.pin = GPIO_PIN_12 | GPIO_PIN_13;
GPIO_InitStructure.mode = GPIO_MODE_AF;
GPIO_InitStructure.otype = GPIO_OTYPE_PP;
GPIO_InitStructure.speed = GPIO_SPEED_100MHz;
GPIO_InitStructure.pupd = GPIO_PUPD_UP;
GPIO_Config(GPIOB, &GPIO_InitStructure);
GPIO_ConfigPinAF(GPIOB, GPIO_PIN_SOURCE_12, GPIO_AF_CAN2);
GPIO_ConfigPinAF(GPIOB, GPIO_PIN_SOURCE_13, GPIO_AF_CAN2);
}
#endif
}
/*
* Copyright (c) 2006-2022, RT-Thread Development Team
*
* SPDX-License-Identifier: Apache-2.0
*
* Change Logs:
* Date Author Notes
* 2025-08-04 flybreak first version
*/
#include <rtthread.h>
#include "mb.h"
#include "mb_m.h"
#ifdef PKG_MODBUS_MASTER_SAMPLE
#define SLAVE_ADDR MB_SAMPLE_TEST_SLAVE_ADDR
#define PORT_NUM MB_MASTER_USING_PORT_NUM
#define PORT_BAUDRATE MB_MASTER_USING_PORT_BAUDRATE
#else
#define SLAVE_ADDR 0x01
#define PORT_NUM 3
#define PORT_BAUDRATE 115200
#endif
#define PORT_PARITY MB_PAR_EVEN
#define MB_POLL_THREAD_PRIORITY 10
#define MB_SEND_THREAD_PRIORITY RT_THREAD_PRIORITY_MAX - 1
#define MB_SEND_REG_START 2
#define MB_SEND_REG_NUM 2
#define MB_POLL_CYCLE_MS 500
static void send_thread_entry(void *parameter)
{
eMBMasterReqErrCode error_code = MB_MRE_NO_ERR;
rt_uint16_t error_count = 0;
USHORT data[MB_SEND_REG_NUM] = {0};
while (1)
{
/* Test Modbus Master */
data[0] = (USHORT)(rt_tick_get() / 10);
data[1] = (USHORT)(rt_tick_get() % 10);
error_code = eMBMasterReqWriteMultipleHoldingRegister(SLAVE_ADDR, /* salve address */
MB_SEND_REG_START, /* register start address */
MB_SEND_REG_NUM, /* register total number */
data, /* data to be written */
RT_WAITING_FOREVER); /* timeout */
/* Record the number of errors */
if (error_code != MB_MRE_NO_ERR)
{
error_count++;
}
}
}
static void mb_master_poll(void *parameter)
{
eMBMasterInit(MB_RTU, PORT_NUM, PORT_BAUDRATE, PORT_PARITY);
eMBMasterEnable();
while (1)
{
eMBMasterPoll();
rt_thread_mdelay(MB_POLL_CYCLE_MS);
}
}
static int mb_master_sample(int argc, char **argv)
{
static rt_uint8_t is_init = 0;
rt_thread_t tid1 = RT_NULL, tid2 = RT_NULL;
if (is_init > 0)
{
rt_kprintf("sample is running\n");
return -RT_ERROR;
}
tid1 = rt_thread_create("md_m_poll", mb_master_poll, RT_NULL, 512, MB_POLL_THREAD_PRIORITY, 10);
if (tid1 != RT_NULL)
{
rt_thread_startup(tid1);
}
else
{
goto __exit;
}
tid2 = rt_thread_create("md_m_send", send_thread_entry, RT_NULL, 512, MB_SEND_THREAD_PRIORITY - 2, 10);
if (tid2 != RT_NULL)
{
rt_thread_startup(tid2);
}
else
{
goto __exit;
}
is_init = 1;
return RT_EOK;
__exit:
if (tid1)
rt_thread_delete(tid1);
if (tid2)
rt_thread_delete(tid2);
return -RT_ERROR;
}
MSH_CMD_EXPORT(mb_master_sample, run a modbus master sample);
4. 使用Modbus Slave进行测试
4.1 Modbus Slave设置- 下载并安装Modbus Slave工具
- 配置串口参数：
- 端口：选择对应的COM口
- 波特率：115200
- 数据位：8
- 停止位：1
- 校验位：None
- 从站地址：1
4.2 Modbus Slave测试
可以对保持寄存器进行读取和设置
5. 总结本文介绍了在Geehy APM32F402R Micro-EVB开发板上基于RT-Thread和Freemodbus实现Modbus主机的过程： - 掌握RT-Thread下Freemodbus的配置和使用
- 理解Modbus主机的工作原理和实现方法
- 学会使用Modbus Slave工具进行通信测试
- 具备扩展更多Modbus功能的能力
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