Modbus

LIBMODBUS的主从机测试例程

发布于 2019-09-26 17:07:47 浏览：6740 订阅该版

20 个回答

whj467467222 认证专家 2019-09-26

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[i=s] 本帖最后由 whj467467222 于 2019-9-26 17:43 编辑 [/i]

这个代码是[https://github.com/loogg/libmodbus](RTT libmodbus 源码仓库)里的，这个是主机例程。我增加了一些自己注释。

```
#include "modbus_rtu_test.h"
#include "modbus.h"
#include "stdio.h"
#include "string.h"

#define RS485_RE GET_PIN(G, 8) //485控制引脚

/*轮询任务*/
static void test_thread(void *param)
{
    uint16_t tab_reg[64] = {0};  //读取数据的缓存区
    modbus_t *ctx = RT_NULL; 
    ctx = modbus_new_rtu("/dev/uart2", 115200, 'N', 8, 1); //根据你要用的那个串口修改这个格式 "/dev/uart1"
    modbus_rtu_set_serial_mode(ctx, MODBUS_RTU_RS485);
    modbus_rtu_set_rts(ctx, RS485_RE, MODBUS_RTU_RTS_UP); //设置485的控制脚
    modbus_set_slave(ctx, 3); //设置从机站号3
    modbus_connect(ctx); //连接
    modbus_set_response_timeout(ctx, 0, 1000000);//超时时间
    int num = 0;
    while (1)
    {
        memset(tab_reg, 0, 64 * 2);//把缓存区的数据格式化为0；
        int regs = modbus_read_registers(ctx, 0, 20, tab_reg); //读取3号从站的0地址开始的20个长度的数据，并把数据存放在tab_reg
```

```
/*打印数据*/
        printf("-------------------------------------------\n");
        printf("[%4d][read num = %d]", num, regs);
        num++;
        int i;
        for (i = 0; i < 20; i++)
        {
            printf("<%#x>", tab_reg[i]);
        }
        printf("\n");
        printf("-------------------------------------------\n");
        rt_thread_mdelay(5000);
    }
    //7-关闭modbus端口
    modbus_close(ctx);

//8-释放modbus资源
    modbus_free(ctx);
}

static int rtu_test_init(void)
{
    rt_pin_mode(RS485_RE, PIN_MODE_OUTPUT);
    rt_thread_t tid;
    tid = rt_thread_create("test",
                           test_thread, RT_NULL,
                           2048,
                           12, 10);
    if (tid != RT_NULL)
        rt_thread_startup(tid);
    return RT_EOK;
}
INIT_APP_EXPORT(rtu_test_init);
```

whj467467222 认证专家 2019-09-26

开源，分享，交流，共同进步

[i=s] 本帖最后由 whj467467222 于 2019-9-26 17:50 编辑 [/i]

这个是从机例程

```
#include "modbus_rtu_test.h"
#include "modbus.h"
#include "stdio.h"
#include "string.h"

#define RS485_RE GET_PIN(A, 8)

static modbus_mapping_t *mb_mapping = NULL;

static void test_thread(void *param)
{
    int rc;
    uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];
    modbus_t *ctx = RT_NULL;
    ctx = modbus_new_rtu("/dev/uart1", 115200, 'N', 8, 1);
    modbus_rtu_set_serial_mode(ctx, MODBUS_RTU_RS485);
    modbus_rtu_set_rts(ctx, RS485_RE, MODBUS_RTU_RTS_UP);
    modbus_set_slave(ctx, 1);
    modbus_connect(ctx);
    modbus_set_response_timeout(ctx, 0, 1000000);
    int num = 0;
    mb_mapping = modbus_mapping_new(MODBUS_MAX_READ_BITS, 0,
                                    MODBUS_MAX_READ_REGISTERS, 0);
    if (mb_mapping == NULL) {
        rt_kprintf("Failed to allocate the mapping: %s\n",
                modbus_strerror(errno));
        modbus_free(ctx);
        return ;
    }
```

```
mb_mapping->tab_registers[0] = 1;//数据缓存区
       mb_mapping->tab_registers[1] = 2;
       mb_mapping->tab_registers[2] = 3;
       mb_mapping->tab_registers[3] = 4;
       mb_mapping->tab_registers[4] = 5;
       mb_mapping->tab_registers[5] = 6;
    
    while (1)
    {
      uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];
        
        rc = modbus_receive(ctx, query);
        if (rc > 0) {
            modbus_reply(ctx, query, rc, mb_mapping);
        } 
```

```
}
}
static int rtu_test_init(void)
{
    rt_pin_mode(RS485_RE, PIN_MODE_OUTPUT);
    rt_thread_t tid;
    tid = rt_thread_create("test",
                           test_thread, RT_NULL,
                           2048,
                           12, 10);
    if (tid != RT_NULL)
        rt_thread_startup(tid);
    return RT_EOK;
}
INIT_APP_EXPORT(rtu_test_init);
```