Table of Contents
The boards are back, populated, and the first bring-up session is done. The short version: it went well.
Working down the list of building blocks —
Power came up cleanly. The MPS battery charger IC is behaving correctly, and the power tree is solid throughout.
Flash and firmware — the STM32U599 is talking to the debugger and I can program it without issues. That's always a relief on a first spin.
Display — the 240 × 960 FPC panel is alive and the image looks great. This is the centrepiece of the whole project and seeing it light up properly for the first time is a good moment.
USB is up and enumerating correctly.
Buzzer/speaker — This I will change. The original design used a simple piezo buzzer, but after thinking more about what the device should actually sound like, I swapped it out for a small but proper speaker with a useful frequency range of around 800 Hz to 8 kHz. It's a physically tiny component but it produces a noticeably more natural sound — more like the click-and-tone feedback of a quality instrument than the harsh beep of a piezo. Worth the change.
Not everything is perfect — first spins never are. There are two things to address in the next revision:
- Component placement needs some minor adjustments. Nothing electrical — a few parts are sitting closer to neighbours than I'd like, which will matter for assembly yield as the design matures.
- The microSD socket needs to be replaced. The part I specified has gone end-of-life, so a drop-in replacement is in progress. Fortunately, most standard microSD footprints are close enough that this should be a straightforward swap.
All the fundamental building blocks are proven. The path to a working calculator is now a software problem, which is a good place to be after a first spin.