PinePhone Pro EDL boot by shorting contacts

[biketool]

Hello! 
I am a new PinePhone user and I recently purchased a PinePhone pro explorer edition. After installing Tow Boot and trying several distributions, I was unable to get voice calling to work. As a result, I attempted to update the modem firmware, thinking that this may be the issue (after no issues with microphone or other audio systems were apparent anywhere). The modem appears to never have booted up properly again, and now the modem is not recognized by the operating system at all.

The reason for this post is because I cannot find the EDL boot test points on the motherboard that are mentioned in several different places (GitHub - Biktorgj/quectel_eg25_recovery: Stock firmware recovery packages for Quectel EG25-G, pinephone_modem_sdk/docs/RECOVERY.md at kirkstone · the-modem-distro/pinephone_modem_sdk · GitHub, https://forum.pine64.org/attachment.php?aid=2843, ...).  The motherboard in my phone does not have these contacts (text on board: "Pinephonepro-V02 2023-0909"). In fact, there is a metal shield attached to the board directly over that area. Is there any way to access these contacts on Pinephone pro explorer edition boards like version 2023-0909?

Thanks for any help!

If you can access the modem by fastboot at all there is no big deal to fix and you will not need EDL flash.  It is an issue with the newer modem modules having a slightly different firmware than the older ones, the modem distro website has the instructions, read this post:
https://forum.pine64.org/showthread.php?tid=19421

Recovery of the EFS area

So, you're probably here because your modem suddenly stopped booting after a failed firmware ugrade or downgrade.

Long story short: something changed in the way Quectel builds their images and it seems like if you got a new board and attempt to flash an older image version the modem will stop being able to read its own EFS area and end up in offline mode with no IMEI.

How do we fix this?

With a bit of patience and a recovery package

    1. Download this: EFS Recovery package https://themodemdistro.com/packs/efs_recovery.tar.gz
    2. Enter fastboot
    3. If you're already running the custom firmware, run fastboot oem stay (I had to use echo -ne "AT+QFASTBOOT\r" > /dev/ttyUSB2 to get fastboot)
    4. Unpack the tar gz (tar -xvf efs_recovery.tar.gz )
    5. Flash the custom bootloader and boot it: fastboot flash aboot appsboot.mbn && fastboot reboot && fastboot oem stay
    6. Flash the placeholder sys_rev image: fastboot flash sys_rev sys_rev.bin
    7. Rebuild your IMEI: fastboot oem fix_imei 12345678901234 (where 12345678901234 is the IMEI as shown in the RF shield on the back of the phone)
    8. Tell the modem to boot again: fastboot continue

This will overwrite your sys_rev partition with a purposedly broken one, to which we'll write a new IMEI, calculate its CRC, and flash to the EFS area. This should allow the modem to go back to previous stock version you want too