import serial,time,struct import modbus_tk.defines as cst from modbus_tk import modbus_rtu # from modbus_tk.utils import create_master_string def main(): # 打开两个串口 com1 = serial.Serial(port='com2', baudrate=38400, bytesize=8, parity='N', stopbits=1) com2 = serial.Serial(port='com3', baudrate=38400, bytesize=8, parity='N', stopbits=1) # 创建Modbus RTU主机(master) master = modbus_rtu.RtuMaster(com1) master.set_timeout(1.0) master.set_verbose(True) # time.sleep(2) # 读取保持寄存器数据 red = master.execute(1, cst.READ_HOLDING_REGISTERS, 0, 9) print(red) red1 = master.execute(1, cst.READ_HOLDING_REGISTERS, 0, 9)[0] # 这里可以修改需要读取的功能码 print(red1) new = int(red1 * 0.98) print(new) master.execute(1, function_code=cst.WRITE_MULTIPLE_REGISTERS, starting_address=0, output_value=[new]) time.sleep(0.5) red = master.execute(1, cst.READ_HOLDING_REGISTERS, 0, 9) print(red,0) # 读取输入寄存器数据 input_regs = master.execute(1, cst.READ_INPUT_REGISTERS, 0, 9) print(input_regs, 1) # 读取输入线圈数据 input_bits = master.execute(1, cst.READ_COILS, 0, 9) print(input_bits, 2) # 读取输出线圈数据 output_bits = master.execute(1, cst.READ_DISCRETE_INPUTS, 0, 9) print(output_bits, 3)。现在将所有读取数据打包为Modbus RTU消息并写入com2串口。要求打包的Modbus RTU消息格式要跟 master = modbus_rtu.RtuMaster(com1)一样

可以使用modbus_tk.modbus_rtu.master._compute_crc函数计算Modbus RTU消息的校验码，并使用struct.pack()函数将消息打包为字节流。以下是代码示例：

import serial
import time
import struct
import modbus_tk.defines as cst
from modbus_tk import modbus_rtu

def pack_modbus_rtu_msg(address, function_code, starting_address, quantity_of_x, output_value=None):
    # 构造Modbus RTU消息
    if output_value is not None:
        data_len = 2 + 2*len(output_value)
    else:
        data_len = 2
    msg = struct.pack(">BBHH", address, function_code, starting_address, quantity_of_x)
    if output_value is not None:
        for val in output_value:
            msg += struct.pack(">H", val)
    # 计算校验码(CRC)
    crc = modbus_rtu.master._compute_crc(msg)
    msg += struct.pack(">H", crc)
    return msg

def main():
    # 打开两个串口
    com1 = serial.Serial(port='com2', baudrate=38400, bytesize=8, parity='N', stopbits=1)
    com2 = serial.Serial(port='com3', baudrate=38400, bytesize=8, parity='N', stopbits=1)
    
    # 创建Modbus RTU主机(master)
    master = modbus_rtu.RtuMaster(com1)
    master.set_timeout(1.0)
    master.set_verbose(True)
    
    # 读取保持寄存器数据
    red1 = master.execute(1, cst.READ_HOLDING_REGISTERS, 0, 9)[0]
    new = int(red1 * 0.98)
    master.execute(1, function_code=cst.WRITE_MULTIPLE_REGISTERS, starting_address=0, output_value=[new])
    
    # 打包Modbus RTU消息并写入com2串口
    msg = pack_modbus_rtu_msg(1, cst.READ_HOLDING_REGISTERS, 0, 9)
    com2.write(msg)
    
    # 读取输入寄存器数据
    input_regs = master.execute(1, cst.READ_INPUT_REGISTERS, 0, 9)
    print(input_regs, 1)
    
    # 读取输入线圈数据
    input_bits = master.execute(1, cst.READ_COILS, 0, 9)
    print(input_bits, 2)
    
    # 读取输出线圈数据
    output_bits = master.execute(1, cst.READ_DISCRETE_INPUTS, 0, 9)
    print(output_bits, 3)