Compute Module • CM4 does not boot(?) on a custom carrier

Hey all,

I have a CM4 that works nicely. Currently it doesn't need/use any peripherals whatsoever, just the USB. I can run my project off the CM4IO board with DC power + USB comms; and I can also run it off the CM5IO board with only the single USB plugged in supplying both power and data.

Now, I made a beyond trivial custom IO board for it. It's like a first version I wanted to see work before going wild... and of course it doesn't work . But I'm not entirely sure why so I wanted to ask if anyone has any ideas.

You can see the schematics below. Just an FYI, it basically has a USB power/data in, has the standard power and activity LEDs as output and 2 RGB LEDs. Nothing else.
Now, what happens is that when I power it on, the power LED comes on (so the power on procedure has to successfully reach at least the 3.3V step) and it stays on. For a brief moment the actvity LED blinks *once*, and never more. Everything gets stuck then. It seems that the power on procedure goes belly up at some point, but I can't understand how. The entire design is so simple that I don't see what can go wrong *after* already reaching a single green blip.

Any ideas would be welcome, I have no idea what I'm doing here at this point.

Statistics: Posted by Karalabe — Fri Mar 07, 2025 6:22 pm — Replies 2 — Views 75

---