Hi njbuch: I read every word of this post. I am in a predicament where I need to get MODBus RTU up and running on the PI under Windows 10 IOT, however, there does not seem to be much support for this (hardware or software). So, bring on as many words as possible, and I will read them to see if I can find some nugget of help.
I never used a RPi or Win 10 core so far, but for MODBUS RTU all you need is a RS485 Transceiver (like the one on the RS485 Gadgeteer Module) connected to a UART on the RPI.
Then you could adopt my MODBUS RTU/TCP Master/Slave library from codeshare to Win 10 core (UWP).
Currently itâs available for NETMF and Windows, so this shouldnât be too hard. https://www.ghielectronics.com/community/codeshare/entry/880