Modbus通信及数据存储读取

1. 存储区代号

代码号	功能
1区	输入线圈
0区	输出线圈
3区	输入寄存器
4区	输出寄存器

2. 功能码

代码	功能
0x01	读取输出线圈
0x02	读取输入线圈
0x03	读取输出寄存器
0x04	读取输入寄存器
0x05	写入单个线圈
0x06	写入单个寄存器
0x0F	写入多个线圈
0x10	写入多个寄存器

3. pymodbus服务器

from pymodbus.server.async_io import StartTcpServer
from pymodbus.datastore import (
    ModbusSequentialDataBlock,
    ModbusServerContext,
    ModbusSlaveContext,
)

datablock = ModbusSequentialDataBlock.create()
context = ModbusSlaveContext(
    di=datablock,
    co=datablock,
    hr=datablock,
    ir=datablock,
    )
single = True

# Build data storage
store = ModbusServerContext(slaves=context, single=single)


if __name__ == '__main__':

	address = ("127.0.0.1", 1502)
	StartTcpServer(
	    context=store,  # Data storage
	    address=address,  # listen address
	  	allow_reuse_address=True,  # allow the reuse of an address
	)

4. libmodbus客户端

#include 
#include 
#include 
#include 
#include 
#include 
#include 


// const uint16_t UT_INPUT_REGISTERS_ADDRESS = 0x1;
const uint16_t UT_BITS_ADDRESS = 0x04;
// const uint16_t UT_INPUT_REGISTERS_NB = 0xA;
// const uint16_t UT_INPUT_REGISTERS_TAB[] = { 0x000A };

int main(int argc, char const *argv[])
{
    int nb = 0x08;
    int rc = 0;
    modbus_t *ctx;
    uint8_t *tab_rp_bits;
    tab_rp_bits = (uint8_t *) malloc(nb * sizeof(uint8_t));
    memset(tab_rp_bits, 0, nb * sizeof(uint8_t));
    ctx = modbus_new_tcp("127.0.0.1", 1502);
    if(ctx == NULL)
    {
        fprintf(stderr, "Unable to allocate libmodbus context\n");
        return -1;
    }

    if(modbus_connect(ctx) == -1)
    {
        fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
        modbus_free(ctx);
        return -1;
    }
    uint8_t data[8] = {1, 0, 1, 0, 1, 1, 0, 1};
    while(1)
    {
        // rc = modbus_write_bit(ctx, UT_BITS_ADDRESS, 1);
        rc = modbus_write_bits(ctx, UT_BITS_ADDRESS, nb, data);
        printf("nb points %d : ", rc);

        rc = modbus_read_bits(ctx, UT_BITS_ADDRESS, 8, tab_rp_bits);
        if (rc != 1) 
        {
            for (size_t i{0}; i < 8; i++)
                // printf("FAILED (nb points %d)\n", rc);
                printf("%d  ", tab_rp_bits[i]);
        }
        printf("\n");
        memset(tab_rp_bits, 0, nb * sizeof(uint8_t));
        sleep(1);
    }
    modbus_close(ctx);
    modbus_free(ctx);
    return 0;
}