I’ve been working on a new version of my Carambola IO board. I’ve added an interrupt line from the MCP23017 back to the Carambola to allow for a trigger when an input changes (save on having to poll the MCP23017 to check for changes!).
One other small change was the addition of a decouple cap close to the pin headers for the Carambola module. It helps to keep the +5V in order, on the first version there was a lot on noise on the 5V line. You can get the new schematic here: Carambola IO Board
I re-generated the artwork, broke out the light box and development kit and got to work “spinning” a new PCB. I’m happy with my timings for exposure and development now and seem to have a repeatable process in place.
The double sided PCB above took about 2 hours from PC screen to etched PCB (not drilled!). Got a good clean PCB with well defined tracks.
Getting the new Carambola module configured was easy. Once connected to the network I could simple copy my Lua MQTT code from my original board over SSH.
Now I have to write some more Lua code to handle the interrupt pin and post the changes on the inputs via MQTT!