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Error message after running "epevermodbus --portname /dev/ttyUSB0 --slaveaddress 1" #27

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Zippo355 opened this issue Apr 26, 2024 · 7 comments
Closed

Error message after running "epevermodbus --portname /dev/ttyUSB0 --slaveaddress 1" #27

Zippo355 opened this issue Apr 26, 2024 · 7 comments

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@Zippo355
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Hi, I'm having issues when running this command ("epevermodbus --portname /dev/ttyUSB0 --slaveaddress 1"):

"raise InvalidResponseError(text)
minimalmodbus.InvalidResponseError: Checksum error in rtu mode: b'\x01?' instead of b'I?' . The response is: b'\x01\x041\x00\x00\x01?' (plain response: b'\x01\x041\x00\x00\x01?')"

My Epever Tracer 1210AN is connected to my Raspberry Pi 4 model B through a USB to RS485 converter (CHT340)
Here is the output for "stty -F /dev/ttyUSB0":

"speed 115200 baud; line = 0;
min = 0; time = 0;
-brkint -icrnl -imaxbel
-opost -onlcr
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke"

I checked also the cabling in-between them with multimeter before actually connecting them together and everything seems to be in order.
@SmithChart
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Can you enable the debugging-feature in the minimalmodbus librabry?
As far as I see there is no feature to do it from the command line by now. But you could patch it in the code:

In https://github.com/rosswarren/epevermodbus/blob/main/epevermodbus/driver.py#L43 add a line self.debug=True
(See: https://github.com/pyhys/minimalmodbus/blob/master/minimalmodbus.py#L124 )

Please provide the output afterwards.

@Zippo355
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Hi, thank you very much for your response!

I added this line after Line43 (self.debug=True) and also on Line124 in minimalmodbus.py, I enabled debug (debug: bool = True), and here is the output:

$ epevermodbus --portname /dev/ttyUSB0 --slaveaddress 1
MinimalModbus debug mode. Create serial port /dev/ttyUSB0
Real Time Data
MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): 01 04 31 00 00 01 3F 36 (8 bytes)
MinimalModbus debug mode. Clearing serial buffers for port /dev/ttyUSB0
MinimalModbus debug mode. No sleep required before write. Time since previous read: 1995926.43 ms, minimum silent period: 1.75 ms.
MinimalModbus debug mode. Response from instrument: 01 04 31 00 00 01 3F (7 bytes), roundtrip time: 0.0 ms. Timeout for reading: 0.0 ms.

MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): 01 04 31 00 00 01 3F 36 (8 bytes)
MinimalModbus debug mode. Clearing serial buffers for port /dev/ttyUSB0
MinimalModbus debug mode. No sleep required before write. Time since previous read: 200.67 ms, minimum silent period: 1.75 ms.
MinimalModbus debug mode. Response from instrument: 01 04 31 00 00 01 3F (7 bytes), roundtrip time: 0.0 ms. Timeout for reading: 0.0 ms.

MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): 01 04 31 00 00 01 3F 36 (8 bytes)
MinimalModbus debug mode. Clearing serial buffers for port /dev/ttyUSB0
MinimalModbus debug mode. No sleep required before write. Time since previous read: 200.62 ms, minimum silent period: 1.75 ms.
MinimalModbus debug mode. Response from instrument: 01 04 31 00 00 01 3F (7 bytes), roundtrip time: 0.0 ms. Timeout for reading: 0.0 ms.

MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): 01 04 31 00 00 01 3F 36 (8 bytes)
MinimalModbus debug mode. Clearing serial buffers for port /dev/ttyUSB0
MinimalModbus debug mode. No sleep required before write. Time since previous read: 200.56 ms, minimum silent period: 1.75 ms.
MinimalModbus debug mode. Response from instrument: 01 04 31 00 00 01 3F (7 bytes), roundtrip time: 0.0 ms. Timeout for reading: 0.0 ms.

MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): 01 04 31 00 00 01 3F 36 (8 bytes)
MinimalModbus debug mode. Clearing serial buffers for port /dev/ttyUSB0
MinimalModbus debug mode. No sleep required before write. Time since previous read: 200.52 ms, minimum silent period: 1.75 ms.
MinimalModbus debug mode. Response from instrument: 01 04 31 00 00 01 3F (7 bytes), roundtrip time: 0.0 ms. Timeout for reading: 0.0 ms.

Traceback (most recent call last):
  File "/home/george/venvs/testare/bin/epevermodbus", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/epevermodbus/command_line.py", line 60, in main
    print(f"Solar voltage: {controller.get_solar_voltage()}V")
                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/epevermodbus/driver.py", line 75, in get_solar_voltage
    return self.retriable_read_register(0x3100, 2, 4)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/retrying.py", line 56, in wrapped_f
    return Retrying(*dargs, **dkw).call(f, *args, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/retrying.py", line 266, in call
    raise attempt.get()
          ^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/retrying.py", line 301, in get
    six.reraise(self.value[0], self.value[1], self.value[2])
  File "/home/george/venvs/testare/lib/python3.11/site-packages/six.py", line 719, in reraise
    raise value
  File "/home/george/venvs/testare/lib/python3.11/site-packages/retrying.py", line 251, in call
    attempt = Attempt(fn(*args, **kwargs), attempt_number, False)
                      ^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/epevermodbus/driver.py", line 49, in retriable_read_register
    return self.read_register(
           ^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/minimalmodbus.py", line 484, in read_register
    returnvalue = self._generic_command(
                  ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/minimalmodbus.py", line 1276, in _generic_command
    payload_from_slave = self._perform_command(functioncode, payload_to_slave)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/minimalmodbus.py", line 1359, in _perform_command
    payload_from_slave = _extract_payload(
                         ^^^^^^^^^^^^^^^^^
  File "/home/george/venvs/testare/lib/python3.11/site-packages/minimalmodbus.py", line 1904, in _extract_payload
    raise InvalidResponseError(text)
minimalmodbus.InvalidResponseError: Checksum error in rtu mode: b'\x01?' instead of b'I?' . The response is: b'\x01\x041\x00\x00\x01?' (plain response: b'\x01\x041\x00\x00\x01?')

I am using a Foiled Twisted Pair Cat5e cable, After cutting the cable, I left out only wires 4(blue) and 6(green). and on the other end of the USB to RS485 converter, I placed to A (D+) the green wire and to B (D-) de blue wire. I was inspired by Adam Welch's video about making a custom cable for communicating with your Epever Tracer (https://www.youtube.com/watch?v=r3LrWeYYtnQ&t=188s&ab_channel=AdamWelch)

@SmithChart
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My guess is, that it is not an issue with your cable, but with the RS485 transceiver: Your transceiver has local echo enabled. So every word written on the bus is also received. This is generally not a bad thing. But we need to tell minimalmodbus that it should handle that for us.

After your self.debug = True please insert another line with self.handle_local_echo = True. Then minimalmodbus should ignore what we are sending.

(I am sure there is a way to do it in the Linux serial stack, too. But I am always confused which flags to set on the line discipline...)

@Zippo355
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After inserting a new line with self.handle_local_echo = True in driver.py I get the same output.

@SmithChart
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Sorry for the delay. (I was on some vacation.) But this riddle still bothers me:

I still suspect that this is a problem in handling the local echo, since MinimalModbus receives back what it has send - but just one byte less.

A few more ideas:

  1. Do you have the option to capture what is actually going on "on the wire"? e.g. with another RS485 transceiver/cable or a logic analyzer?
  2. Let's try a few more options on Minimalmodbus:
    2.1) After self.handle_local_echo = True set self.precalculate_read_size = False. Let's see if this already changes something. But I do not think that this will do the trick.
    2.2) After self.precalculate_read_size = False add another "self.serial.timeout = 1.0`. This will lead to very long timeouts for each transaction. But maybe something here is very slow and we thus do not capture the whole transmission from the bus.

@Zippo355
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Zippo355 commented May 17, 2024 via email

@SmithChart
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Great to hear this solved the problem. Good to know that is is a problem of the cable or a combination of cable and how Minimalmodbus tries to use it.

Feel free to close the issue when it is resolved for you.

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@SmithChart @Zippo355