First of all, Hi everyone.
I am developing a PCB for a client to interface the CM with an industrial installation.
My design uses a quite complex PSU design but using off the self step-up/down modules i keep it as simple as possible.
(The UPS part is realized using Super Capacitors.)
In this version of the PCB there was a footprint mismatch with the soDIMM socket an it is hand soldered and for this the pins 1 through 39 (odds only) are not soldered (and removed from the socket).
- PROBLEM #1 (possibly same reason as #2)
To correctly boot the CM the PCB should be unused for several hours or discharged the capacitors (super and small electrolytic), fired up for a second or two and then reseted.
After booting and log in through serial console everything works ok until first halt/poweroff/reboot. When happens one of these the CM is fried. After testing the pins one by one I figured out that the GPIO0-27_VREF is shorted to Ground!
Four (4) times happened 4 modules dead.
So... can anyone suggest anything that will help?
I am waiting some new modules today but I can't afford to destroy any more.