树莓派通过Modbus RTU读取施耐德PM5100电能表数据报错求助

我的目标是在树莓派上运行Python脚本，通过Modbus RTU协议读取施耐德PM5100电能表的kWh数据。此前我用相同方案成功读取过SDM220 Modbus电表，但调试PM5100始终无法成功。

已确认配置信息 #

• PM5100参数：
  • 从站地址：1
  • 波特率：19200
  • 校验位：无
• 接线情况：已确认正常，GND和屏蔽层未连接，D1、D0引脚通过RS485转USB连接器对接。

测试代码 #

#!/usr/bin/python3

import minimalmodbus

mb = minimalmodbus.Instrument("/dev/ttyUSB0", 1)
mb.serial.baudrate = 19200
mb.debug = True

val = mb.read_float(3212,3,4)
print(val)

报错日志 #

运行后抛出InvalidResponseError错误，日志如下：

MinimalModbus debug mode. Will write to instrument (expecting 13 bytes back): 01 03 0C 8C 00 04 86 B2 (8 bytes)
MinimalModbus debug mode. Clearing serial buffers for port /dev/ttyUSB0
MinimalModbus debug mode. No sleep required before write. Time since previous read: 439371243.54 ms, minimum silent period: 2.01 ms.
MinimalModbus debug mode. Response from instrument: 7F 7E DE CE F7 F3 13 (7 bytes), roundtrip time: 0.1 ms. Timeout for reading: 50.0 ms.

Traceback (most recent call last):
  File "1.py", line 9, in <module>
    val = mb.read_float(3212,3,4)
  File "/usr/local/lib/python3.7/dist-packages/minimalmodbus.py", line 717, in read_float
    payloadformat=_Payloadformat.FLOAT,
  File "/usr/local/lib/python3.7/dist-packages/minimalmodbus.py", line 1245, in _generic_command
    payload_from_slave = self._perform_command(functioncode, payload_to_slave)
  File "/usr/local/lib/python3.7/dist-packages/minimalmodbus.py", line 1330, in _perform_command
    response, self.address, self.mode, functioncode
  File "/usr/local/lib/python3.7/dist-packages/minimalmodbus.py", line 1867, in _extract_payload
    raise InvalidResponseError(text)
minimalmodbus.InvalidResponseError: Checksum error in rtu mode: 'ó\x13' instead of '\\>' . The response is: '\x7f~ÞÎ÷ó\x13' (plain response: '\x7f~ÞÎ÷ó\x13')

已完成排查 #

• 不确定使用的寄存器地址是否正确，但更换其他寄存器地址也无法正常读取
• 排除库不兼容问题，minimalmodbus库此前读取SDM220电表完全正常
• 尝试改用read_register方法、调整相关参数也没有效果

恳请有相关调试经验的朋友提供思路、建议或解决方案，非常感谢！

参考资料 #

• PM5100产品页：链接
• 寄存器列表：链接
• RS485转USB转换器：链接
• minimalModbus文档：链接

内容的提问来源于stack exchange，提问作者Ewoud Adams