Using OpenPLC on Raspberry pi, UniPi seems good selection to connect 24V sensors, motors, etc.
What is the common way to connect 24V device to OpenPLC on PC?

For using arduino as a OpenPLC slave,
we can find 24V I/O shields, such as
and 24V ready arduino, as
https://tctec.net/top16_ii.htm .
Are these modules ready to run OpenPLC Slave runtime?
Or, is it better to use modbus RTU or TCP 24V slave devices?
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The biggest problem with these boards is the pinout. You will probably have to modify OpenPLC firmware to match the inputs and outputs on the boards, and then it should be fine.
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