ModbusTCP timeout settable from Config>Port dialog

[tofublock]

I'm implementing a client device for Artisan as a ModbusTCP slave and sometimes my device doesn't respond quite fast enough for Artisan, as its read timeout is fixed to be min(0.2s, samplingtime/2) - so basically always 200ms. Setting the timeout to something like 0.5s fixes this problem for me and communication works well with fewer interruptions.

Allowing the timeout for ModbusTCP to be set from the "Config>Port" dialog would fully solve my problem. The timeout field that is there is currently only used for SerialModbus connections, but could be used for the same purpose without the need to change anything else.

[AppVeyorBot]

✅ Build artisan f196774 (523) completed (commit f196774c9d by @tofublock)

[MAKOMO]

Hi, this sounds like a good idea, but might have consequences for all the MODBUS TCP machine setups which do not explicitly set the timeout. Any specific reason for this change?

Note: there is a major upgrade of pymodbus just being finalized which might resolve existing MODBUS communication issues.

[MAKOMO]

Ah, just found your note in the corresponding issue. I will process this change and make sure it will not disturb anything else.

[tofublock]

Thanks for taking a look.

To prevent issues with existing setups, how about something like this instead?
timeout=min((self.aw.qmc.delay/2000), self.timeout if self.timeout > 0 else 0.2)

Re pymodbus, I did notice some irregularities in the Modbus requests but assumed my device to be to blame (e.g. receiving individual read register requests when set to "optimize" or "fetch full blocks".) I haven't gotten around to investigating this further (partly because my implementation works well enough now as is), but one bulk request per 0.5s is much more feasible for a slow client than 10 small requests in the same time.
If I can help with the pymodbus 3.0 switch let me know!

[AppVeyorBot]

✅ Build artisan c82232a (524) completed (commit c82232acb3 by @tofublock)

[MAKOMO]

Explicit MODBUS timeout parameter added. Thanks for your input!