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pyhys / minimalmodbus

Easy-to-use Modbus RTU and Modbus ASCII implementation for Python.
Apache License 2.0
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How to send a non-standard function code #86

Open larrybarello opened 2 years ago

larrybarello commented 2 years ago

For a particular vendor, a custom function code ($78) with a payload of 0x0000, 0x0001, causes a reset to factory defaults. The response appears to be an echo of the request.

Is this possible without modifying minimalmodbus code?

i'm a newbie and attempted a subclass, and ran into trouble pretty quick when making a stripped down "read" method that just jammed in the values.

Could a generic write be exposed and allow the user jam in OEM functions? Or maybe a magic method that overrides the function code on the next transaction? Then the user can pick the closest transaction, override the function code. In my case "read_register(0)" and poke in the $78 This is an ugly solution, but presumably the user would know what they are doing if they tried it.

edit: this particular vendor also uses 0xFF as the broadcast address :(

pyhys commented 1 year ago

Hi! It is possible to use the _perform_command() functionality as described in https://minimalmodbus.readthedocs.io/en/stable/develop.html#extending-minimalmodbus

Note that it is outside the official API and is subject to future changes.

larrybarello commented 1 year ago
Unfortunately, for my project I need to use 0xFF for the “broadcast” address and MinimalModbus only allows 0-247  For some reason known only to Renogy, they changed the broadcast address for their smart lithium batteries from 0 to 0xFF.   Thanks for the pointer to the dev documents.  Is there any reason I cannot just modify the code to allow 0xFF as an Broadcast adx?  I rummaged around the code a bit but was overwhelmed and dropped it.  I have more energy now and could revisit it again. Larry From: Jonas BergSent: Wednesday, July 5, 2023 10:19 AMTo: pyhys/minimalmodbusCc: larry Barello; AuthorSubject: Re: [pyhys/minimalmodbus] How to send a non-standard function code (Issue #86) Hi!It is possible to use the _perform_command() functionality as described inhttps://minimalmodbus.readthedocs.io/en/stable/develop.html#extending-minimalmodbusNote that it is outside the official API and is subject to future changes.—Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you authored the thread.Message ID: ***@***.***>