We have a buildroot image that we plan rolling on all our embedded systems quite soon.
Except... we have an issue with *SOME* CM3s (about 4 every 50 units processed).
Basically, when these "faulty" CM3s are booted, the activity LED stays always ON.
From what I understand this means there is a corruption issue.
Except when we flash these CM3s we checksum them after and compare the checksum
to the image's checksum (our image, the buildroot one) and the checksums match perfectly
every single time, which means the image was written OK (we use direct IO to checksum,
so no buffering gets in the way here).
Yet they won't boot (act. LED always ON when booting, no blinking whatsoever).
Please note that only 4 in 50 do this, the 46 others work perfectly fine.
Now when we flash Raspbian Buster into these "faulty" CM3s, they work!!! So we wonder
what it could be. I have almost zero means to test anything because well I can't boot them
(all I get is a black screen on the "faulty" ones).
Perhaps someone with a better RPi experience than mine can give me some insights, I know
this isn't something easy to diagnose given the info I gave.