Hi,
I just wanted to introduce myself and our open-source project SolarNetwork. We collect data from kWh meters, solar inverters, solar charge controllers, industrial switches, weather sources and other items. We really like the look of the Orange Pi zero as a SolarNode target board - that is our client software application. Anyway here is a recent post about how we are using SolarNode to collect data from a thermopile pyranometer using our generic Modbus Device plugin:
http://solarnetwork.net/v4/testing-the-modbus-device-plugin/
Thanks! John