Had chance today to sit and debug the Tenda Homeplug interface. All the work for this was previous done by the OpenROV folk, so I just had to copy it. As previous reported, I managed to position the Tenda board too near the end of the daughterboard and had to use cables to connect to it. It also turned out that I put the GND pin on the wrong side of the connector. An easy fix since I was already using cables. It also turned out that I'd routed a tiny wire to bring power to the Tenda board; so I had to use an extra wire to bring power in since that proved insufficient.

That all done, the Tenda board in the ROV now talks to the test board in my workbench which is fabulous. I've also tried running power over my test tether, and that all works too.