Finally sorted that weird boot message on my pocket Pico build

Ran into the same thing last year with a little weather station I built for the greenhouse. Mine runs off a cheap power bank hanging on a nail, and the first time I unplugged it from the PC I got that same boot message and assumed the flash had corrupted somehow. Re-flashed the firmware twice before I figured out the board was just doing its job. The trick that finally settled it for me was putting a print at the very top of my script that shows the boot time and a short status line on the screen. Once I could see my own text appear right under that boot message, it clicked that the message is just the board talking to you, not a fault.

One thing I do differently from what you described: I left a tiny delay at the start of main.py, maybe a second or two, before my menu loads. On mine, the screen sometimes needed a beat to settle after power-up, and jumping in too fast gave me a blank display even though the code was running fine. If your handheld ever shows a dark screen on battery but works over USB, that might be it.

Mine has been booting cold into the display loop for months now without a hiccup, through winter temperatures in that greenhouse too.

Funny how that same line meant the opposite thing for me. I built a little pond temperature logger with a Pico and an e-ink display, and for weeks I thought my setup was fine because the board booted and drew the reading every morning. Then one day I watched it boot cold and realised the message was the only honest thing on the screen. My main.py had a bug that only showed up when the DS18B20 sensor was unplugged, so on battery it would crash silently before the script got anywhere. The boot line was basically the board telling me it was on its own, and I had been ignoring my own hint.

Same relief here with a little timer box I built for my chicken coop door. Ran it off a usb power brick and spent an evening convinced the flash was toast becuase of that boot line. What actually got me later wasn't the message at all, it was the power brick going to sleep. Cheap ones shut off if the draw is too low, and my board idles light enough to trip it. Random reboots, and I nearly blamed the code again. Swapped in a brick meant for low power stuff and it's been solid since. If anyone's project boots fine on the bench but acts haunted on battery, check the supply before you touch a single line of code.

Glad I found this thread before I tore anything apart. I've only been messing with a Pico for a couple weeks and mine's plugged into an old phone charger, not a battery, so I wasn't even sure my situation counted. Still got that line on boot and spent an evening googling wether it meant the flash was write protected or somthing.

One thing I'm still fuzzy on, does the message show up even if there's no main.py saved yet? Mine prints it either way as far as I can tell, wich is part of why I assumed it was a fault. Might just be my copy of the firmware behaving differently.

That boot line had me chasing ghosts too, but mine turned out to be a hardware thing hiding behind it. My little garage door reminder board would boot fine off USB and then act flaky on batteries, and I kept re-reading the standalone message like it was a clue. A cheap multimeter from the junk drawer was what acutally cracked it, I poked around while it ran on batteries and watched the voltage sag every time the screen drew. Turned out one spring in the battery holder wasn't making good contact. Bent it back with a screwdriver and it's been rock solid since. Worth checking your supply actually holds up under load before trusting the message itself.