The trap closes in stages. We obviously need X - which, as it turns out, requires Y, which means Z1 and Z2, and before anyone knows what’s going on, we’re weeks deep in a “simple feature”.
When that starts to happen, it’s worth revisiting X to see if there’s another way. Software development is like a depth-first traversal of a maze - after all, you’re generally interested in reaching the exit as quickly as possible, not in the overall shortest path - but if a path starts getting longer, a bit more breadth-first time can be worthwhile.
Additional requirement: it must be reliable and fail-safe. If I don’t trust it, I’ll go back to checking the time.
Problem: After brief experimentation, the Pi doesn’t have a backup battery for its realtime clock. Further consultation with the user reveals that part of the “reliable” constraint is “Don’t require any action other than plugging into power, and don’t assume that power is present during the day”. The Pi won’t know when it’s 5am.
We’ll connect the Pi to wifi, and it’ll get the time via NTP on startup.
This “simple” task turns complex; though it’s a Pi Zero W, it can’t see my router on its default frequency. I do end up getting it working (via reconfiguring the router), but it’s a ludicrously overcomplicated and fragile solution and it took longer than it should have.
It also requires a full 5W of power, meaning a full-size USB adapter (not a tiny phone charger). And it’s dependent on my local wifi network, so it won’t work when travelling, once that’s a thing again.
Worse, with an initial solution in place, the user starts coming up with enhancements. Since we’re running a full computer now, we could create a web interface, accessible from a phone, to allow configuring the alert time. If I go to bed late, perhaps that shouldn’t be until 05:30.
Totally doable, but… seems awkward, and triggers my “this is harder than I think it should be” alarm. Time to revisit the design.
The third pass uses a Raspberry Pico microcontroller, and uses the lack-of-power-during-the-day as a feature. 6.5 hours after you plug it in, it toggles the LED. Though there’s an onboard button (and plenty of pins to solder on more), it’s not even needed.
It’s a much neater solution, and working well in production.
: Being able to repeatedly check the actual time during the night makes insomnia worse. But giving up at 4am makes for a bad day. A reasonable compromise is “after 5am, you may (rather than must, which is how normal alarm clocks work) get up”.