Compute Module 22-pin vs 15-pin CSI Interface

[lothar98]

Hello everyone,

I'm currently designing a custom carrier board for the Compute Module 3+. I intend to have at least one (possibly two) CSI ports on the board, but I'm confused about the connectors. I can see in the documentation that both the Pi Zero and Compute Module IO board use a 22-pin connector which has 3 extra ground pins and 4 NC pins compared to the 15-pin connector used in other versions of the Pi.

So from what I understand, electrically there's no difference between the two connectors (correct me if I'm wrong). Is it possible to design the custom board with the 15-pin connector, to avoid having to use an adapter/special cable? If so, what is the reason that the Pi Zero and CMIO board are designed with the 22-pin connector?

[rpdom]

The Pi Zero has the small 22-pin connector due to size.

The CM has the 22 pin connector because one of the CSI ports has a 4-lane interface, whilst the other one (the same as used on all the Pis) only has a 2-lane interface.

If you are only using the 2-lanes you can use teh 15 pin connector.

[lothar98]

I'm not sure how, but I missed the fact that the 22-pin connector is more compact. It makes a lot more sense now. Thanks!

[6by9]

If you check the CMIO schematics, then you'll see that the CAM1 connector (J11) uses all the pins.

CSI2 supports a configurable number of data lanes, each able to carry up to 1Gbit/s of data (potentially more). In the SoC CAM0 only has 2 data lanes available, whilst CAM1 has 4, hence CAM1 needing all 22 pins for CAM1_D[P|N]2 and CAM1_D[P|N]3 plus associated grounds.