【python linux 上 RS485通信 Modbus协议】从来好事天生俭，自古瓜儿苦后甜。这篇文章主要讲述python linux 上 RS485通信 Modbus协议相关的知识，希望能为你提供帮助。
如题:
CRC计算参考了这篇文章
后来发现在读取的时候会出问题, 所以引入了. serial
import struct
import platform
import time
import serial #导入模块
sysstr = platform.system()
#RS485文件的通信地址,在开发板上是/dev/ttysWK0
if(sysstr=="Windows"):
RS485FileName = "COM1"
elif(sysstr =="Linux"):
RS485FileName = "/dev/ttysWK0"
# RS485：/dev/ttysWK0
# RS232：/dev/ttysWK1
# UART2：/dev/ttysWK3
# UART1：/dev/ttysWK2
else:
RS485FileName = "/dev/ttysWK0"
# ===============================================================
def CalCRC16(data, length):
#print(data, length)#打印数据，长度
crc=0xFFFF
if length == 0:
length = 1
j = 0
while length != 0:
crc ^= list.__getitem__(data, j)
#print(j=0x%02x, length=0x%02x, crc=0x%04x %(j,length,crc))
for i in range(0,8):
if crc & 1:
crc > > = 1
crc ^= 0xA001
else:
crc > > = 1
length -= 1
j += 1
return crc
# ===============================================================
def CRCBuffer(buffer):
crc_transformation = CalCRC16(buffer,len(buffer))
#crc_calculation = hex(crc_transformation)
#print(crc_calculation:,crc_calculation)
tasd = [0x00,0x00]
tasd[0] = crc_transformation & 0xFF
tasd[1] = (crc_transformation > > 8) & 0xFF
H =hex(tasd[0])
L =hex(tasd[1])
H_value = https://www.songbingjia.com/android/int(H,16)
L_value = https://www.songbingjia.com/android/int(L,16)
buffer.append(H_value)
buffer.append(L_value)
return buffer
# ===============================================================
# if __name__ == __main__:
#print(CRCBuffer(buffer))
def Send485CMD_OLD(cmd):
global RS485FileName
with open(RS485FileName, "wb") as rs485:
buffercrc = CRCBuffer(cmd)
ret = rs485.write(bytes(buffercrc))
rs485.close()
return ret
def SendAndRead485CMD(cmd):
global RS485FileName
ser = serial.Serial(RS485FileName,9600,timeout=10)
buffercrc = CRCBuffer(cmd)
print("RS485 TX => ", bytes(bytearray(buffercrc)))
ser.write(buffercrc) # 这里直接发送int类型的数据, 内部会自动转换成byte字节.
# ret = ser.write(bytes(buffercrc))
time.sleep(0.2)
res = ser.read_all()
print("RS485 RX => ", res)
ser.close()
return res
def ReadGateSate(gatenum):
cmd = [
gatenum, #设备地址=\\x00# 0x00 is guang bo
0x03, #功能码=\\x06 #\\06 is write, \\03 is read, \\10 is write mutil
0x00, #寄存器地址高=\\x00
0x18, #寄存器地址低=\\x0E #0E is open door cmd
0x00, #数据高=\\x00
0x01, #数据低=\\x01
# 0x00, #CRC高=\\x00
# 0x00, #CRC低=\\x00
]
return SendAndRead485CMD(cmd)
def OpenTheDoor(gatenum):
cmd = [
gatenum, #设备地址=\\x00# 0x00 is guang bo
0x06, #功能码=\\x06 #\\06 is write, \\03 is read, \\10 is write mutil
0x00, #寄存器地址高=\\x00
0x0E, #寄存器地址低=\\x0E #0E is open door cmd
0x00, #数据高=\\x00
0x01, #数据低=\\x01
# 0x00, #CRC高=\\x00
# 0x00, #CRC低=\\x00
]
SendAndRead485CMD(cmd);
pass
def CloseTheDoor(gatenum):
cmd = [
gatenum, #设备地址=\\x00# 0x00 is guang bo
0x06, #功能码=\\x06 #\\06 is write, \\03 is read, \\10 is write mutil
0x00, #寄存器地址高=\\x00
0x0E, #寄存器地址低=\\x0E #0E is open door cmd
0x00, #数据高=\\x00
0xFF, #数据低=\\x01
# 0x00, #CRC高=\\x00
# 0x00, #CRC低=\\x00
]
SendAndRead485CMD(cmd);
pass
def OpenTheLid(gatenum):
cmd = [
gatenum, #设备地址=\\x00# 0x00 is guang bo
0x06, #功能码=\\x06 #\\06 is write, \\03 is read, \\10 is write mutil
0x00, #寄存器地址高=\\x00
0x0E, #寄存器地址低=\\x0E #0E is open door cmd
0x00, #数据高=\\x00
0x01, #数据低=\\x01
# 0x00, #CRC高=\\x00
# 0x00, #CRC低=\\x00
]
SendAndRead485CMD(cmd)
pass
def CloseTheLid(gatenum):
cmd = [
gatenum, #设备地址=\\x00# 0x00 is guang bo
0x06, #功能码=\\x06 #\\06 is write, \\03 is read, \\10 is write mutil
0x00, #寄存器地址高=\\x00
0x0E, #寄存器地址低=\\x0E #0E is open door cmd
0x00, #数据高=\\x00
0xFF, #数据低=\\x01
# 0x00, #CRC高=\\x00
# 0x00, #CRC低=\\x00
]
SendAndRead485CMD(cmd);
pass
res = OpenTheDoor(0x04)
res = ReadGateSate(0x04)
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