I've been working on the design of a custom CM5 carrier board which I've had manufactured and assembled through PCBWay. The (4 layer) board is largely functional. The CM5 boots - both from USB via the USB-C connector for programming of the eMMC and from eMMC after programming. Power light and eMMC lights work. The ADCs (on the back) are functioning correctly. As is the secondary Micro SD Card (via sdio) and +24 VDC alarm connection. There are two things that aren't: the display connector and the fan connector. I'll post separately about the latter.
When I insert the cable that comes with the RPi Touch Display 2 into the display connector:
And attempt to power up the board, nothing happens. No power light. No eMMC light. Note that I'm attaching the cable without even attempting to attach the display! I can remove the cable (with the power disconnected of course), plug in power again, and the board comes right up.
I have, of course, used the KiCad design for the RPi Compute Module 5 IO Board as reference when designing my board. The relevant bits of my schematic are:
The connector I used is the Hirose Electric FH12-22S-0.5SVA(54): https://www.hirose.com/en/product/p/CL0586-0813-6-54
Now there was a question from PCBWay as to the proper orientation of this connector during board assembly. Unfortunately the footprint allows the connector to be reversed and still assembled. And I found it somewhat difficult to interpret the mechanical drawings on the dataset to determine which was the "1" pin. So there is the possibility that I messed that up and that the connector is reversed.
What seems strange to me, however, is that the cable could cause the board to not boot without a display attached. But the connectors on each end of the cable are not the same. So I don't know if there is some amount of interconnection within the cable itself that, combined with an incorrectly installed connector, could result in the board not booting.
Any ideas? I can provide some snapshots of the PCB layout too if needed.
Thanks in advance for any help or ideas you can provide!
When I insert the cable that comes with the RPi Touch Display 2 into the display connector:
I have, of course, used the KiCad design for the RPi Compute Module 5 IO Board as reference when designing my board. The relevant bits of my schematic are:
Now there was a question from PCBWay as to the proper orientation of this connector during board assembly. Unfortunately the footprint allows the connector to be reversed and still assembled. And I found it somewhat difficult to interpret the mechanical drawings on the dataset to determine which was the "1" pin. So there is the possibility that I messed that up and that the connector is reversed.
What seems strange to me, however, is that the cable could cause the board to not boot without a display attached. But the connectors on each end of the cable are not the same. So I don't know if there is some amount of interconnection within the cable itself that, combined with an incorrectly installed connector, could result in the board not booting.
Any ideas? I can provide some snapshots of the PCB layout too if needed.
Thanks in advance for any help or ideas you can provide!
Statistics: Posted by William Hachfeld — Sat Feb 21, 2026 5:39 pm — Replies 4 — Views 48