Watch sometimes resets upon wakeup

[jorticus]

Only seems to happen when the watch has been left alone for a while. OLED display appears to briefly power-up before resetting the MCU. Reset flags usually report a brown-out.

My best guess at the moment is a power supply issue, caused by the OLED supply drawing too much current on start-up.

I've tried adding 20uF of capacitance across the main VDD, but perhaps I should place this closer to the MCU? Maybe I could add an inductor between the regulator and the MCU?

[jorticus]

I've tried adding extra capacitance and even series inductance between VCC and the MCU, but there is no improvement to the voltage sag.

I've realised the watch isn't actually reporting a brown-out reset, and it only occurs after some amount of time, so perhaps it's a kernel issue? What happens if I leave it turned on for a long time?

[jorticus]

So it's not a power or wakeup issue at all, I have found the watch resets if I just leave it alone on my desk for an hour. Very likely something to do with my kernel, but it's a bit hard to debug since it takes so long to happen. The actual time it takes seems to vary, and I haven't yet timed it.