modbus python

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def print_hi(name):
# 在下面的代码行中使用断点来调试脚本。
print(f’Hi, {name}') # 按 Ctrl+F8 切换断点。
############################################
###############################
import serial
import crcmod
import time
import struct

CRC16校验，返回整型数

def crc16(veritydata):
if not veritydata:
return
crc16 = crcmod.mkCrcFun(0x18005, rev=True, initCrc=0xFFFF, xorOut=0x0000)
return crc16(veritydata)

校验数据帧的CRC码是否正确

def checkcrc(data):
if not data:
return False
if len(data) <= 2:
return False
nocrcdata = data[:-2]
oldcrc16 = data[-2:]
oldcrclist = list(oldcrc16)
crcres = crc16(nocrcdata)
crc16byts = crcres.to_bytes(2, byteorder=“little”, signed=False)
# print(“CRC16:”, crc16byts.hex())
crclist = list(crc16byts)
if oldcrclist[0] != crclist[0] or oldcrclist[1] != crclist[1]:
return False
return True

Modbus-RTU协议的03或04读取保存或输入寄存器功能主-》从命令帧

def mmodbus03or04(add, startregadd, regnum, funcode=3):
if add < 0 or add > 0xFF or startregadd < 0 or startregadd > 0xFFFF or regnum < 1 or regnum > 0x7D:
print(“Error: parameter error”)
return
if funcode != 3 and funcode != 4:
print(“Error: parameter error”)
return
sendbytes = add.to_bytes(1, byteorder=“big”, signed=False)
sendbytes = sendbytes + funcode.to_bytes(1, byteorder=“big”, signed=False) + startregadd.to_bytes(2, byteorder=“big”, signed=False) +
regnum.to_bytes(2, byteorder=“big”, signed=False)
crcres = crc16(sendbytes)
crc16bytes = crcres.to_bytes(2, byteorder=“little”, signed=False)
sendbytes = sendbytes + crc16bytes
return sendbytes

Modbus-RTU协议的03或04读取保持或输入寄存器功能从-》主的数据帧解析（浮点数2,1,4,3格式，16位短整形（定义正负数））

def smodbus03or04(recvdata, valueformat=0, intsigned=False):
if not recvdata:
print(“Error: data error”)
return
if not checkcrc(recvdata):
print(“Error: crc error”)
return
datalist = list(recvdata)
if datalist[1] != 0x3 and datalist[1] != 0x4:
print(“Error: recv data funcode error”)
return
bytenums = datalist[2]
if bytenums % 2 != 0:
print(“Error: recv data reg data error”)
return
retdata = []
if valueformat == 0:
floatnums = bytenums / 4
print("float nums: ", str(floatnums))
floatlist = [0, 0, 0, 0]
for i in range(int(floatnums)):
floatlist[1] = datalist[3+i4]
floatlist[0] = datalist[4+i4]
floatlist[3] = datalist[5+i4]
floatlist[2] = datalist[6+i4]
bfloatdata = bytes(floatlist)
[fvalue] = struct.unpack(‘f’, bfloatdata)
retdata.append(fvalue)
print(f’Data{i+1}: {fvalue:.3f}')
elif valueformat == 1:
shortintnums = bytenums / 2
print("short int nums: “, str(shortintnums))
for i in range(int(shortintnums)):
btemp = recvdata[3+i2:5+i2]
shortvalue = int.from_bytes(btemp, byteorder=“big”, signed=intsigned)
retdata.append(shortvalue)
print(f"Data{i+1}: {shortvalue}”)
return retdata

if name == ‘main’:
slaveadd = 2
startreg = 1
regnums = 1
send_data = mmodbus03or04(slaveadd, startreg, regnums)
print("send data : ", send_data.hex())
com = serial.Serial(“com3”, 9600, timeout=0.8)
starttime = time.time()
com.write(send_data)
recv_data = com.read(regnums*2+5)
endtime = time.time()
if len(recv_data) > 0:
print("recv: “, recv_data.hex())
print(f"used time: {endtime-starttime:.3f}”)
com.close()
smodbus03or04(recv_data)

###############################
#############################################

按间距中的绿色按钮以运行脚本。

if name == ‘main’:
print_hi(‘PyCharm’)

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