MinimalModbus IO误差

Question

我试图通过Modbus RTU-半双工RS-485连接从我的windows机器(windows 10)与自定义板通信。我正在使用python，并安装了所有依赖库。我也有合适的RS-422/485适配器。我知道波特率、COM端口、从地址和奇偶位都是正确的.我还知道我的代码正在从O-作用域跟踪输出一个比特流。由于某些原因，董事会根本不会做出回应。任何帮助都将不胜感激。

import minimalmodbus
import serial 

#minimalmodbus.CLOSE_PORT_AFTER_EACH_CALL = True 
minimalmodbus.PARITY = serial.PARITY_EVEN
#minimalmodbus.handle_local_echo=True
minimalmodbus.BAUDRATE = 57600
minimalmodbus.TIMEOUT = .01
instrument = minimalmodbus.Instrument('COM4',0)
instrument.debug = True
print(instrument.read_register(11,1))

MinimalModbus debug mode. Writing to instrument (expecting 7 bytes back): '\x00\x03\x00\x0b\x00\x01ô\x19' (00 03 00 0B 00 01 F4 19)
MinimalModbus debug mode. No sleep required before write. Time since previous read: 1478637162864.7 ms, minimum silent period: 0.67 ms.
MinimalModbus debug mode. Response from instrument: '' () (0 bytes), roundtrip time: 10.9 ms. Timeout setting: 10.0 ms.

Traceback (most recent call last):
  File "RS485.py", line 11, in <module>
    print(instrument.read_register(11,1))
  File "C:\Users\mtangy\AppData\Local\Programs\Python\Python35-32\lib\site-packages\minimalmodbus.py", line 258, in read_register
    return self._genericCommand(functioncode, registeraddress, numberOfDecimals=numberOfDecimals, signed=signed)
  File "C:\Users\mtangy\AppData\Local\Programs\Python\Python35-32\lib\site-packages\minimalmodbus.py", line 697, in _genericCommand
    payloadFromSlave = self._performCommand(functioncode, payloadToSlave)
  File "C:\Users\mtangy\AppData\Local\Programs\Python\Python35-32\lib\site-packages\minimalmodbus.py", line 795, in _performCommand
    response = self._communicate(request, number_of_bytes_to_read)
  File "C:\Users\mtangy\AppData\Local\Programs\Python\Python35-32\lib\site-packages\minimalmodbus.py", line 930, in _communicate
    raise IOError('No communication with the instrument (no answer)')
OSError: No communication with the instrument (no answer)

Answer 1

问题就在眼前：

instrument = minimalmodbus.Instrument('COM4',0)

您正在指示minimalmodbus使用modbus id等于零的仪器。这是一个无效的身份证明。

检查仪器的设置并更正代码中的id。

Answer 2

尝试使用instrument = minimalmodbus.Instrument('COM4',1)设置从id，其中1是自定义工具的从ID。

并尝试使用以下行增加超时值参数

minimalmodbus.TIMEOUT = 1，其中1等于1000毫秒。