A project log for OSHWatch

An open-source "smart watch" that can be built from easily available parts, and assembled by hand. Designed for hackers

Jared SansonJared Sanson 08/16/2014 at 05:060 Comments

So I've been tackling a rather tricky bug recently, where the whole watch would reset sometimes after waking up from sleep. I believe I have tracked the cause down to the voltage sagging too much and causing a brownout, as you can see in the following oscilloscope trace:

Unfortunately I can't seem to fix it, I've tried adding an inductor in series with the MCU, along with a 20uF capacitor, but neither have any affect on the above trace. This is probably due to the fact the OLED draws up to 100mA on start up.

I think the only way I can fix this is to disable the brown-out reset altogether, or perhaps I can figure out a way to soft-start the OLED.

Also, my bluetooth chips are on their way, so hopefully I can solder them in soon!