我是Modbus协议的新手，我使用minimalmodbus python包从Modbus RTU slave获取数据。slave是L&T Quasar Module。 Python代码如下：
import minimalmodbus
import serial
import sys
instrument = minimalmodbus.Instrument('/dev/ttyUSB0', 1)
instrument = minimalmodbus.Instrument('/dev/ttyUSB0', 1,mode='rtu')
instrument.mode = minimalmodbus.MODE_RTU # rtu or ascii mode
instrument.serial.baudrate = 9600 # Baud
instrument.serial.bytesize = 8
instrument.serial.parity = serial.PARITY_EVEN
instrument.serial.stopbits = 1
instrument.serial.timeout = 0.05 # seconds
print instrument.read_register(30001, 2) #register address, number of registers
输出结果为：
*Traceback (most recent call last):
File "Desktop/meter/minimal_test.py", line 16, in <module>
print instrument.read_register(30001, 2) #register address, number of registers
File "/usr/local/lib/python2.7/dist-packages/minimalmodbus-0.7-py2.7.egg/minimalmodbus.py", line 258, in read_register
return self._genericCommand(functioncode, registeraddress, numberOfDecimals=numberOfDecimals, signed=signed)
File "/usr/local/lib/python2.7/dist-packages/minimalmodbus-0.7-py2.7.egg/minimalmodbus.py", line 697, in _genericCommand
payloadFromSlave = self._performCommand(functioncode, payloadToSlave)
File "/usr/local/lib/python2.7/dist-packages/minimalmodbus-0.7-py2.7.egg/minimalmodbus.py", line 798, in _performCommand
payloadFromSlave = _extractPayload(response, self.address, self.mode, functioncode)
File "/usr/local/lib/python2.7/dist-packages/minimalmodbus-0.7-py2.7.egg/minimalmodbus.py", line 1088, in _extractPayload
raise ValueError('The slave is indicating an error. The response is: {!r}'.format(response))
ValueError：从站指示错误。答案是：＆＃39; \ x01 \ x83 \ x02 \ xc0 \ xf1＆＃39; *
奴隶在Windows机器上使用MODSCAN按预期响应。