p18clock update 2025

Long after the p18clock hobby project stalled (2012), a number of updates came in for 2025 – some based on the latest changes in libledmtx merged last year, e.g. the support for user-defined viewports. This makes it possible to have a larger framebuffer than the actual physical display and to define which part of it is visible.

This feature is now leveraged by the AUTO mode in p18clock to simulate vertical scrolling text (where the framebuffer is large enough to hold up to four lines of text, and the viewport is updated to show only a part of it). This obviously requires a libledmtx build that has ENABLE_VIEWPORT=1.

Here is the list of firmware changes:

• Automatic repetition of key presses
• Improved sampling of LM35 temperature sensor
• Enhanced AUTO mode with vertical scroll (time, day-of-week, date, and temperature).

Additionally, a couple of changes went in for the prototype board:

• Added missing 10 nF decoupling capacitors
• Installed a proper (micro-USB-B) power connector
• Desoldered LM35 temperature sensor from the board and attached it via a small pigtail cable. Special care has to be taken as the analog LM35 output is highly vulnerable to EMI.

Last but not least, Kicad is being used to produce the circuit schematic and PCB design. The resulting Gerber file will be sent to jlcpcb for fabrication; components to be manually soldered when the PCBs are delivered. I’ll post updates here as soon as this progresses!