I have, so far, been unsuccessful in upgrading my HA Yellow to the CM5. Using my Lenovo laptop was a complete failure for some reason. RPIBoot would not recognize the USB device. I have had success using my Dell desktop machine, i.e RPIBoot runs successfully but RPI Imager does not see any storage. Installing the CM5 on an RPI IO module was successful after adding a memory card to the IO card.
After many unsuccessful attempts, I have acquired a USB NVMe adapter with the plan to load the image directly on the NVMe. Now, I hesitate because overwriting out the contents of the NVMe means that if this should not work for some reason, my HA system will be down until I can find a solution.
I have been reading articles about the boot process for the CM series and find information that conflicts with the Nabu Casa procedure for updating the HA Yellow.
My thinking now is that unlike computers with which I am familiar, that have BIOS firmware to interface with system hardware and control the booting process, the RPI CM devices require the RPIBoot process to create a bootable USB drive. One dissertation describes loading the USB device via RPIBoot, disconnecting power, USB, removing USB boot jumper (or switch), repowering to have CM module boot up. This is different from the Nabu Casa procedure or any other procedure concerning the HA Yellow upgrade.
I may be able to create an image of the NVMe prior to overwriting for restoring in case all goes tits up. My confusion is that if the CM5 is made bootable via the RPIBoot procedure why does an image need to be loaded since the NVMe already has a working image on it? Shouldn’t the CM5 naturally boot the existing NVMe image?
Update: I have successfully backed up the NVMe image and wrote the HA Yellow generic image with RPI Imager. Unfortunately the CM5 would not boot. Replacing the CM4 module has it booting and I am currently recovering my backup from earlier today.