2026-03-17 (Tu) VictorianLightPiano IO expander boards populated

Each octave should be identically wired, except for the address jumpers on the IO expander boards. I planned to get one board done today and finish the other two when I knew what to expect. I laid out the IO expanders on a prototyping PCB and imagined where to place the resistors. Given the boards' dimensions, I decided to keep the resistors underneath the demo boards, which I propped up with header pins and sockets. The arrangement meant that my inputs would have their wires land on the outside, since they required pull-up resistors connected to Vcc, while the outputs required resistors in series, but I had to mount them vertically and land the wires under the demo boards. I decided to replicate this pattern rather than run wires to the switches and LEDs.

I soldered one of the headers in the wrong position by one row, and it was the input version. When I realized the mistake, I already had the resistors populated, so I had to abandon it, find a new prototype PCB, and start over. Instead of soldering 72 resistors, I installed 96. The day's work was pretty significant, and all I have left, soldering-wise, is the lights, pushbuttons, and troubleshooting.

Three usable boards and a mistake

The rest of the posts for this project have been arranged by date.
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Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
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Completed projects from year 10
Completed projects from year 11
Completed projects from year 12

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2026-03-04