Oops, pifinder actually wasn't done
Oops. NOW my Sliced PiFinder is done.
The original PiFinder uses a $50 USB GPS module. To avoid spending $50, I wrote some code to fake a GPS. Eventually the dev brickbots switched PiFinders to a $10 solderable GPS module that uses UART instead of USB, and $10 felt reasonable, so I bought one and soldered it in. I thought I was done and that all I had to do was edit the software to remove my fake GPS code and use the regular GPS code! I was wrong - the GPS didn’t connect.
My Sliced PiFinder uses a raspberry pi 3 but the PiFinder was designed for a raspberry pi 4. I thought the only difference was CPU speed, but there’s more: the instructions asked me to solder the GPS to two pins which couldn’t speak UART on a pi 3 but could on a pi 4. Oops.
The Pi 3 has only one pair of GPIO pins that can speak UART: 14 and 15. By default it’s used for a “linux serial console”, but you can configure it for custom use (like listening to GPS) by adding enable_uart=1 in /boot/config.txt.
So I desoldered my GPS, attached it to pins 14 and 15 with some truly janky soldering (pic above), fixed a “NMEA unknown msg” problem by turning off echo according to comments here, edited gpsd.conf, and now GPS is finally working.
...for real this time