python - pymodbus:请求创建和响应接收

Question

谁能解释如何通过 Modbus TCP/IP 使用 pymodbus 以正确的方式创建请求并获得响应？

我有 PLC，我想将其用作从站，PC 用作主站。

我尝试这样做:

from pymodbus.client.sync import ModbusTcpClient

host = '192.168.56.9'
port = 502   

client = ModbusTcpClient(host, port)
client.connect()

#Register address 0x102A (4138dec) with a word count of 1
#Value - MODBUS/TCP Connections
#Access - Read
#Description - Number of TCP connections

request = client.read_holding_registers(4138, 1) 
response = client.execute(request)

print response

>>> ReadRegisterResponse (1)

Answer 1

设置unit参数并使用print(request.registers)代替print(request)。

这是一个例子:

request = client.read_holding_registers(4138, 1, unit=1)  # Set unit argument.

if not request.isError():
    '''isError() method implemented in pymodbus 1.4.0 and above'''
    print(request.registers)  # Your problem is here.

else:
    # Do stuff for error handling.
    print('Error message: {}'.format(request))