Can I rewrite a non-bootable eMMC from the PBP itself?

[Kicou]

I was playing with different OS images and decided that since I was able to successfully boot from SD card it would be OK to overwrite the eMMC module image.

I dd'ed a Rock64Pro (bionic-minal arm64) onto the eMMC and now it won't boot anymore, neither from eMMC nor SD.

I was able to eventually start from SD by disabling the eMMC via the internal switch, but since I can't see it I cannot write to it.

How can enable the eMMC but bypass it at boot in order to rewrite it from the PBP itself (I don't have any other equipment to which I can attach the eMMC).

I have enabled the serial connector and do have a serial console adapter that I can connect to a Linux box, and probably attach to via minicom.

[bcnaz]

I believe in some other posts I have seen, you can re-activate the eMMC switch after booting. (?)

[Kicou]

I was able to interrupt the boot sequence via serial console.
I can now boot from my SD and see the eMMC block device, so I should be able to write a new image onto it from there

[Arwen]

For others that may be reading this thread, here is a reference to the eMMC disable switch;

Wiki - Pinebook Pro - Key Internal Parts

Eventually we will get a clearer idea of how to use the eMMC disable switch. I vaguely recall someone saying that you start the PBP with the eMMC disabled, wait a few seconds, and then switch it back to enabled. Thus, you would be able to boot off a SD card and then fix the eMMC. Requires the bottom to be open... but better than a brick :-).