Saturday, January 9, 2016

Reverse engineering a hot tub

I changed the water in my hot tub today and so I had a lot of time on my hands, so I took the controller cover off and tried to figure out how it works. My main purpose was to try to figure out how the control panel interfaces, mainly so that I can contemplate some kind of remote monitoring interface. I know that some models of Balboa controllers have WiFi options, so I figured there must be a communications interface somewhere. There definitely is. The existing (very simple) control panel is connected via an 8-pin RJ-45, and there's a spare one right next to it. There is one removable chip on the board labeled with something looking like a version number. I peeled the sticker off and, surprise it's a PIC18F2420 microcontroller. That's great - I already have programming tools and a C compiler for that. My next step is to try to find a schematic for this board. If I can do that then the feasibility of entirely replacing the control software is high. The hardest part probably would be figuring out how to talk to their existing control panel.