04-10-2017, 07:42 PM
(This post was last modified: 04-10-2017, 07:54 PM by TinkerBear.)
I sorta had my doubts that it could be the power supply, so I sat down to do some rigourous testing - three different power supplies to try, recording fluctuations on the power input (DC in and 5V lines) via Euler header and a DSO (Siglent SDS1052DL).
The good news is that there's not much to see on the power line. Some fluctuations, but no major departures that I can see.
The bad news is... No crash when running off my bench power supply. Definite repeatable crashes on both a "PQI" brand 3.4A USB charger and a cheap chinese 5V3A micro-USB charger. For giggles, I tried a genuine Apple iPad 2.1A charger - these things are generally regarded as very well made, with little ripple and high reliability... and it crashes. Different iPad charger... still crashes.
It crashes (mostly) just after "[ 13.159862] cfg80211: Calling CRDA to update world regulatory domain". No idea why, I've had my WiFi/BT module disconnected for all this testing.
The average current pulled by the board is only around 0.3A. Is there a decoupling capacitor missing somewhere?
Let's try bodging a 10µF low ESR tantalum capacitor on the 5V power rail on the Euler connector... no crash with bench power supply, still crashes with PQI wall wart. Maybe the 3.3v rail would be better... nope.
Maybe I'm missing the obvious solution - bin this POS and buy an RPi 3.
Wait - ONE MORE THING TO TRY - move that 10µF cap to the DC IN pin of the Euler connector... And I'm booted and running off the PQI supply. But not the 5V3A chinese supply. Let's try that again. Yep, works on 2nd try. Hmmm, maybe bigger capacitor.
The good news is that there's not much to see on the power line. Some fluctuations, but no major departures that I can see.
The bad news is... No crash when running off my bench power supply. Definite repeatable crashes on both a "PQI" brand 3.4A USB charger and a cheap chinese 5V3A micro-USB charger. For giggles, I tried a genuine Apple iPad 2.1A charger - these things are generally regarded as very well made, with little ripple and high reliability... and it crashes. Different iPad charger... still crashes.
It crashes (mostly) just after "[ 13.159862] cfg80211: Calling CRDA to update world regulatory domain". No idea why, I've had my WiFi/BT module disconnected for all this testing.
The average current pulled by the board is only around 0.3A. Is there a decoupling capacitor missing somewhere?
Let's try bodging a 10µF low ESR tantalum capacitor on the 5V power rail on the Euler connector... no crash with bench power supply, still crashes with PQI wall wart. Maybe the 3.3v rail would be better... nope.
Maybe I'm missing the obvious solution - bin this POS and buy an RPi 3.
Wait - ONE MORE THING TO TRY - move that 10µF cap to the DC IN pin of the Euler connector... And I'm booted and running off the PQI supply. But not the 5V3A chinese supply. Let's try that again. Yep, works on 2nd try. Hmmm, maybe bigger capacitor.