Today I made a lot of progress on my Hackpad PCB. I started with a simple 3-key layout, but then decided I wanted to make the project bigger and more useful, so I changed the design to a 12-key macropad with a 3×4 key matrix, one rotary encoder, and an OLED connector. A lot of the time went into figuring out how the matrix was supposed to work. At first I was wiring the switches like they were chained together, but that was wrong, so I rebuilt it using rows and columns. I added 12 diodes, one for each switch, so the keyboard can avoid ghosting when multiple keys are pressed. I kept the diodes on the top side of the PCB because they fit fine and I think it will be easier to solder that way. After finishing the schematic, I assigned all the footprints, including the Cherry MX switch footprints, 1N4148 diode footprints, the XIAO footprint, the EC11 rotary encoder footprint, and a 1x4 pin header for the OLED. Then I moved everything into the PCB editor and spent a while arranging the layout. I wanted it to look kind of like a clean macropad with the keys on the left and the knob/OLED area on the right. Routing was definitely the most annoying part. I had a bunch of overlapping traces at first, and my first DRC run had a lot of errors, including shorts, clearance issues, and traces going too close to the board edge. I had to delete and reroute some traces, use both copper layers, and make sure the rows, columns, encoder, OLED, power, and ground were all connected correctly. Eventually I got the PCB to pass DRC with 0 errors and 0 unconnected items. The only warnings left were silkscreen warnings, which are not a big deal.