I had a Pro-Lite display that I had picked up cheap without any communication cable, or any software, lying around in my shop. At least I had the remote, but it was slow and I never thought I would actually use it like that. It was high time that I got around to making a cable and looking into the protocol, so I thought that I would share my findings here.
My goal was to be able to update the sign from Processing and thereby be able to use it interactively in some way. It was a two step process, first I needed a cable, secondly I needed the protocol. Researching on the interwebs, I was able to find (as we all are) all the information I needed and now I will share this information in one location here, at our first and favourite 'how-to' stop.
Step 1: Hunter and Gatherer
Things that you need
A Pro-Lite Display Sign (try online, I lucked out in finding mine)
A four wire telephone cable (RJ12) - look closely and see how many wires there are, six will also work, but four is simpler, a phone extension from the dollar store will usually have four.
A female serial DB9 Connector – I picked mine up at my local shop, they are easy enough to find online as well.
a crimp connector or some wire strippers with a crimper built in