- 监测数据采集物联网应用开发步骤(9.2)
Modbus rtu协议开发
本章节在《监测数据采集物联网应用开发步骤(7)》基础上实现可参考《…开发步骤(7)》调试工具，本章节代码需要调用modbus_tk组件，阅读本章节前建议baidu熟悉modbus rtu协议内容
组件安装modbus_tk
pip3 install modbus_tk
验证是否安装成功，python中运行下列代码无异常则安装成功：
importmodbus_tk
新建modbus协议管理类com.zxy.comport.ComModBus.py
#! python3# -*- coding: utf-8 -'''Created on 2020年05月10日@author: zxyong 13738196011'''import time,structfrom com.zxy.common import Com_Parafrom com.zxy.common.Com_Fun import Com_Funfrom com.zxy.z_debug import z_debugimport modbus_tk.defines as cstimport modbus_tk.modbus_rtu as modbus_rtu#监测数据采集物联网应用--modbus协议管理类class ComModBus(z_debug):def __init__(self):pass@staticmethoddef get_objAryRtuMaster(inputComPort):master = Com_Fun.GetHashTableNone(Com_Para.objAryRtuMaster, inputComPort)if master is None:com_at = Com_Fun.GetHashTableNone(Com_Para.htComPort, inputComPort)if com_at is not None:master = modbus_rtu.RtuMaster(com_at.attSerial) # 设定串口为从站master.set_timeout(5.0)master.set_verbose(True)Com_Fun.SetHashTable(Com_Para.objAryRtuMaster, inputComPort, master)return master#字符串转16进制字节并+crc16校验，传入参数无crc校验@staticmethoddef get_data_com_nocrc(inputComPort, CmdStr):temReturn = None try:com_at = Com_Fun.GetHashTable(Com_Para.htComPort, inputComPort)inputByte = bytes().fromhex(CmdStr)inputByte = inputByte + ComModBus._getCrc16(inputByte)if com_at.WritePortData(inputByte) > 0:temReturn = com_at.attReturnValuecom_at.attReturnValue = Noneexcept Exception as e:temReturn = Nonereturn temReturn#字符串转字节发送,ascii发送@staticmethoddef get_data_com_ascii(inputComPort, CmdStr):temReturn = None try:com_at = Com_Fun.GetHashTable(Com_Para.htComPort, inputComPort)inputByte = bytes(CmdStr, encoding="utf8")if com_at.WritePortDataImmed(inputByte) > 0:temReturn = com_at.attReturnValuecom_at.attReturnValue = Noneexcept Exception as e:temReturn = Nonereturn temReturn#字符串转16进制字节发送@staticmethoddef get_data_com_hex(inputComPort, CmdStr): temReturn = Nonetry:com_at = Com_Fun.GetHashTable(Com_Para.htComPort, inputComPort)inputByte = bytes().fromhex(CmdStr)if com_at.WritePortData(inputByte) > 0:comValue = com_at.attReturnValueif comValue is None:return NonetemReturn = comValuecom_at.attReturnValue = Noneexcept Exception as e:temReturn = Nonereturn temReturn#字节发送@staticmethoddef get_data_com_byte(inputComPort, inputByte):temReturn = None try:com_at = Com_Fun.GetHashTable(Com_Para.htComPort, inputComPort)if com_at.WritePortData(inputByte) > 0:comValue = com_at.attReturnValueif comValue is None:return NonetemReturn = comValuecom_at.attReturnValue = Noneexcept Exception as e:temReturn = Nonereturn temReturn#Modbus 04功能码发送@staticmethoddef get_data_rtu_04(inputComPort, inputModbusAddr, inputModbusBegin, inputModbusLength):red = []try:master = ComModBus.get_objAryRtuMaster(inputComPort)if master is not None:red = master.execute(int(inputModbusAddr), cst.READ_INPUT_REGISTERS, int(inputModbusBegin), int(inputModbusLength))# 这里可以修改需要读取的功能码 time.sleep(0.1)if isinstance(red, list) or isinstance(red, tuple): return redelse:return [""]except Exception as e:return [""]#Modbus 03功能码发送 @staticmethoddef get_data_rtu_03(inputComPort, inputModbusAddr, inputModbusBegin, inputModbusLength):read = []try:master = ComModBus.get_objAryRtuMaster(inputComPort)if master is not None:read = master.execute(inputModbusAddr, cst.READ_HOLDING_REGISTERS, inputModbusBegin, inputModbusLength)# 这里可以修改需要读取的功能码 time.sleep(0.1)if isinstance(read, list) or isinstance(read, tuple): return readelse:return [""]except Exception as e:return [""]#Modbus 写寄存器数据@staticmethoddef set_data_rtu(inputComPort, inputModbusAddr, inputModbusBegin, inputValue):read = []try:master = ComModBus.get_objAryRtuMaster(inputComPort)if master is not None:# 这里可以修改需要读取的功能码 if isinstance(inputValue, list) or isinstance(read, tuple):read = master.execute(inputModbusAddr, cst.WRITE_MULTIPLE_REGISTERS, inputModbusBegin, output_value=inputValue) else:read = master.execute(inputModbusAddr, cst.WRITE_SINGLE_REGISTER, inputModbusBegin, output_value=inputValue) if isinstance(read, list) or isinstance(read, tuple): return readelse:return [""]except Exception as e:return [""]@staticmethoddef set_data_rtu2(inputComPort, inputModbusAddr, inputModbusBegin, inputValue):read = []try:master = ComModBus.get_objAryRtuMaster(inputComPort)if master is not None:# 这里可以修改需要读取的功能码 if isinstance(inputValue, list) or isinstance(read, tuple):read = master.execute(inputModbusAddr, cst.ANALOG_INPUTS, inputModbusBegin, output_value=inputValue) else:read = master.execute(inputModbusAddr, cst.ANALOG_INPUTS, inputModbusBegin, output_value=inputValue) if isinstance(read, list) or isinstance(read, tuple): return readelse:return [""]except Exception as e:return [""]@staticmethoddef _getCrc16(RtuStr):b = 0xA001# 16位寄存器a = 0xFFFFfor byte in RtuStr:# 1、把数据帧中的第一个8位字节与CRC寄存器中的低字节进行异或运算a = a ^ bytefor i in range(8):# 3、如果最低位为1：将CRC寄存器与一个预设的固定值（0A001H）进行异或运算if a & 0x0001:a = a >> 1a = a ^ b # 2、将CRC寄存器向右移一位，最高位填以0，最低位移出并检测else:a = a >> 1aa = '0' * (6 - len(hex(a))) + hex(a)[2:]# 获取低和高位lo, hh = int(aa[:2], 16), int(aa[2:], 16)hexbytes = bytes([hh, lo])return hexbytes #高低位 reverse: true高位在前 false低位在前@staticmethoddef ReadFloat(n1, n2, reverse=False):n = '%04x' % n1m = '%04x' % n2if reverse:v = n + melse:v = m + ny_bytes = bytes.fromhex(v)y = struct.unpack('!f', y_bytes)[0]y = round(y, 6)return y@staticmethoddef WriteFloat(value, reverse=False):y_bytes = struct.pack('!f', value)y_hex = ''.join(['%02x' % i for i in y_bytes])n, m = y_hex[:-4], y_hex[-4:]n, m = int(n, 16), int(m, 16)if reverse:v = [n, m]else:v = [m, n]return v@staticmethoddef ReadDint(n1,m1, reverse=False):n ='%04x' % n1m = '%04x' % m1if reverse:v = n + melse:v = m + ny_bytes = bytes.fromhex(v)y = struct.unpack('!i', y_bytes)[0]return y@staticmethoddef WriteDint(value, reverse=False):y_bytes = struct.pack('!i', value)y_hex = ''.join(['%02x' % i for i in y_bytes])n, m = y_hex[:-4], y_hex[-4:]n, m = int(n, 16), int(m, 16)if reverse:v = [n, m]else:v = [m, n]return vmodbus rtu测试案例MonitorDataCmd.py主文件中编写：
from com.zxy.comport.ComModBus import ComModBus在if__name__ == ‘__main__’:下添加
#串口配置参数Com_Para.ComPortList = "COM2,9600,8,0,A;COM4,9600,8,2,B"#串口连接初始化Init_Page.Start_ComPort()#Modbus-rtu协议功能测试temA01modbus = ComModBus()#利用modbus_tk组件获取数据，参数:COM索引,modbus站地址,modbus起始位,modbus长度read = temA01modbus.get_data_rtu_03("A",1,0,10)print("获取10进制原始返回值=>"+str(read))modValue = []iIndex = 0.0n1 = 0n2 = 0for temSV in read:if iIndex % 2 != 0:n2 = int(temSV)#16进制单精转浮点temMV = temA01modbus.ReadFloat(n1,n2,True)modValue.append(temMV)else:n1 = int(temSV)iIndex = iIndex + 1print("获取读到并解析的寄存器浮点数=>"+str(modValue))#利用modbus指令协议直接通过com口读取数据temCmd = "010300A1000A942F"bhex = temA01modbus.get_data_com_hex("A",temCmd)read = str(binascii.b2a_hex(bhex).decode(Com_Para.U_CODE)).upper()print("获取16进制返回值=>"+str(read))运行测试结果如下图:
测试案例中例举了2种方法都可以读到数据，任取其一即可。
针对
#利用modbus指令协议直接通过com口读取数据
temCmd = “010300A1000A942F”
指令解释如下:
01 站地址
03 功能码
00A1 寄存器开始地址(16进制)
000A 读取数据长度10个(16进制转10进制)
942F CRC校验码
获取16进制返回值=>010314429DA8F643060A3D420070A44343000043554CCD49A8返回值解释如下:
01 站地址
03 功能码
14 数据长度20(16进制转10进制)
429DA8F643060A3D420070A44343000043554CCD 数据值16进制
49A8 CRC校验码
429DA8F643060A3D420070A44343000043554CCD 数据值解析要依据相关对方开发说明文档，假设该数据为寄存器浮点数则按如下解析：
429D A8F6 ==>10进制浮点数 78.83
4306 0A3D ==>10进制浮点数 134.039
4200 70A4 ==>10进制浮点数 32.11
4343 0000 ==>10进制浮点数 195
4355 4CCD ==>10进制浮点数 213.300
可以利用该工具计算IEEE 754浮点数十六进制相互转换(32位,四字节,单精度)
在线进制转换-IEE754浮点数16进制转换