Jack.MeterEye wrote: ↑
Thu Sep 27, 2018 1:45 am
Apart from the PCB layout need to be take care, does this “undocumented mode of operation” need any software changes to support it? Thanks.
The stock foundation supplied firmware with other open source software, including Raspbian, appears to work okay with Pi 3B boards which have the non-datasheet configuration so I would have expected it to work if replicating that same non-datasheet configuration LAN9514 hardware for a CM3.
It would seem unlikely that the firmware were coded to only allow the non-datasheet configuration on an actual Pi 3B board but it is possible. Given that pin naming and connections differ between the BCM2835 on a CM1 and a Pi B, and the camera seems to be handled differently depending on whether a CM or Pi board, you might have to reverse engineer a Pi 3B to fully determine what differs from a CM3 replicating a 3B board and a real Pi 3B board, at least to the extent of all connections to the SoC and LN9514.
Probably the best way to see if the non-datasheet configuration works with a CM3 is, as suggested earlier, try it; develop prototype boards which can be used either way, test and analyse the results.