PMON Driver

[mslaffin]

Opening this up for discussion of initial work of the ProcessMonitor subsystem and DP16 driver.

Hardware: DP16PT-330-C24
Communication Manual: PMON digital meter RS-485 communication manual.pdf

[mslaffin]

[mark11778]

section 6.1 page 34 RS-485 communication manual

[mark11778]

appendix C page 53 RS-485 communication manual

[mark11778]

Big-endian

[mslaffin]

Just so everyone is aware, we shouldn't have to worry about explicitly dealing with byte structure or CRC calculations when using pymodbus.

These low level requirements are already implemented at various levels by pymodbus. For example, the FramerRTU class handles the CRC check here

[mark11778]

Ope thanks for the heads up, Ill have to look into this library

[mslaffin]

I'm thinking we'll want a method to interpret the scaling of the "process value" that we're reading from register 39. They provide register 8 (RDGCNF) which I believe stands for "Reading Configuration" and can be used to determine this decimal place.

They have this format table in section 5.7.2 (iSeries protocol settings), but don't have a corresponding table in the Modbus section. I think this is consistent across protocols.

This shows the decimal position is encoded in the last 3 bits of RDGCNF:

[mslaffin]

At this point, I think this branch is safe to merge into develop and shouldn't pose a risk to the existing subsystems. I'm going to merge and close this but I'll open up a follow-up PR for clean-up and any changes that might come up during testing.