I built a new clock, and now I'm not sure what time it is

A man with a watch knows what time it is.

Mentioned in this video (some links are affiliate links):

- Excuse me, what precise time is it? https://media.ccc.de/v/39c3-excuse-me-what-precise-time-is-it
- PTP Wallclock open source project: https://github.com/Gemini2350/ptp-wallclock
- My blog post on the setup: https://www.jeffgeerling.com/blog/2026/ptp-wall-clock-impractical-too-precise/
- Geerling Engineering video on the Blues game and PTP: https://www.youtube.com/watch?v=8Ar4wmA4ujM
- Video on the Pico GPS mini rack clock: https://www.youtube.com/watch?v=E5qA4fgdS28
- Video on the Mitxela Precision Clock Mk IV: https://www.youtube.com/watch?v=aBDgD032DEI

Parts needed for the build:

- Raspberry Pi 4 B: https://www.raspberrypi.com/products/raspberry-pi-4-model-b/
- Adafruit RGB Matrix HAT: https://www.adafruit.com/product/2345
- (2x) Waveshare 64x32 LED RGB Matrix Panel: https://www.waveshare.com/RGB-Matrix-P3-64x32.htm
- 3D Printable joining bracket: https://www.printables.com/model/1624778-ptp-wall-clock-bracket-waveshare-rgb-matrix-connec/collections
- DC 5V 4A power supply: https://amzn.to/3P1I8XG
- 32GB microSD card: https://amzn.to/3NhlGJE

Support me on Patreon: https://www.patreon.com/geerlingguy
Sponsor me on GitHub: https://github.com/sponsors/geerlingguy
Merch: https://www.redshirtjeff.com
2nd Channel: https://www.youtube.com/@GeerlingEngineering
3rd Channel: https://www.youtube.com/@Level2Jeff

Contents:

00:00 - Excuse me, what time is it?
02:01 - Parts required to build a PTP clock
03:14 - Building a precise clock
04:32 - Software for controlling the matrix
05:26 - It works!
06:06 - Keeping it together
07:17 - The problem...
09:04 - It's a timing bug
11:36 - Back in the box