To transmit TMCC commands to the remote nodes, we need something that will read output from the Command Base and send those commands over the RFM69 radio link. If you have a serial connection to your command base, like a SER2, you can use that to interface with the serial data. But then you need to power the transmitting board with another supply, and worry about whether you're shorting the Command Base earth ground to track common. So I designed a simple interface that plugs into the LCS PDI interface, and powers the transmitting Moteino from the LCS 12V supply. The board is just a plug for the PDI cable, and a RS-232 to 3.3v TTL converter. I used the ADM3203ANZ because it was cheapest, but any MAX3232-type chip that can run on 3.3v should work as well. (We need 3.3V because the Moteino runs on 3.3v).
Here's the PDI interface board, and installed as a shield on the Moteino:
Gerbers for this board are here.
The next post will describe the software end of things.