Does this schematic look ok, or do I need to tie the GND from the U socket to GND from the external PSU?
by definition, GND from the mainboard input will be linked to the GND on all sockets. The diagram you show there has the GNDs connected as I would see you need. You haven’t drawn the DP power module, but I assume you’re using one. in that case, after the split off of the input 9v2a power supply to the Cerb and the custom extender, you need to show the DP module on the lines leading to the cerb. Then you’re powering the Cerb from the DP, and you’re providing the custom extender with 9v power. Are you then regulating that down to some other level to be used by the GPRS board?
This is the Fez Cerberus, it has onboard power, so no DP socket needed. The GPRS modem has a voltage regulator (MIC29302WU).
Do you mean Cerbuino? Or Cerb40 with onboard reg? Cerberus does not have onboard power to the best of my knowledge nor the images on the GHI catalog.
Yes, fez cerb bee. Sorry, been a long weekend