Morningstar Modbus interface.
Here's a schematic for a simple adapter from EIA-232 to Morningstar's half-duplex TTL level Modbus (via their 6P6C/6P4C, aka "RJ12") jack. It doesn't have the opto-isolation of the official one. It works with MSView . Requires "good" EIA-232 voltage levels, likely more than the TTL levels put out by some cheap USB-serial adapters (not fully explored - it works with a "good" adapter). The "official" one requires the same.
I'm also working on an ESP-8266 wireless module interface to the same. I've got the hardware and 99% of the Modbus comms working (I can read all the registers/coils), along with a JSON interface for reading stuff. If there's anyone who's AJAX savvy (I've got jquery available) who would like to add to it, PM me. The goal is to have access to Morningstar (maybe more) stuff available via a web(ajax) interface, json and maybe even a Modbus TCP to RTU gateway all running on a low cost, open source, WiFi module.
(Oh, and Morningstar's documentation is full of errors, as can be seen from some of the values above, if you can read them)