Unbrick Nova Air C

nonex · 05-13-2022, 04:52 PM

Hi everyone,

I wanted to experiment a bit and tried using a custom TWRP recovery on my Nova Air C. After doing a fastboot flash recovery twrp.img and fastboot boot twrp.img (following the wrong instructions) I am stuck in the bootloader, unable to enter either recovery or fastboot. With an edl-cable I got a copy of my partitions. But I have no working image I could flash in edl-mode.

Does anybody know what else to do or could provide a working boot.img?

Renate · 05-13-2022, 05:26 PM

Get the 3.2.2 update. Decrypt it with DeBooxUpd.py (Google it). Extract boot.img Flash it.
http://firmware-us.boox.com/fbddd5e0...cbc/update.upx
MD5 = fbddd5e0b6de5d32f2111d6177619cbc
Onyx/NovaAirC/NovaAirC:11/2022-04-23_15-11_3.2.2_559727551f/32979:user/dev-keys

nonex · 05-14-2022, 03:50 AM

Thanks for the link. I decrypted the upx file, and dumped the partitions inside payload.bin. I tried flashing on both a and b partitions, but this unfortunately did not fix the issue. I also tried flashing all partitions inside. (aside from system, vendor and product, because I don't see those partitions.)

I noticed, that the boot.img of the update is the same as my boot_b, but all the a-Partitions are marked as active. Maybe It would help, if I can set the b-partition as active? The Python edl-tool has that option but it does not seem to be working. When calling "edl --loader=662.elf setactiveslot b" I got:

Code:

firehose - [LIB]: Error:['INFO: Calling handler for patch', 'ERROR: patch size too large 128']

Do you have any more ideas?

Renate · 05-14-2022, 07:02 AM

Oops, I misread what you said. I thought that you had flashed TWRP to both recovery and boot. Theoretically flashing boot with boot.img from the update shouldn't be a problem.

It's unfortunate that "boot" is used in different contexts, it breeds confusion. You can "fastboot flash" an image or you can "fastboot boot" an image, they are a bit unrelated. The "gold standard" is writing an image to a partition (using edl, fastboot or adb dd) then doing a reset. I've seen lots of cases (which I couldn't nail down) where "fastboot boot" doesn't start up correctly, probably because of cmdline getting confused? In many cases "fastboot boot" does work and if it does it's an easy way to try out an image without writing anything to flash. If you do hit problems it's worth trying with the "gold standard".

Don't go crazy flashing things. You might be digging yourself a bigger hole.

Some people have had problems where the only thing that changed was the A/B slot somehow. Fastboot can also flip A/B and I would trust that a bit more than the Python EDL. The process involves relabling the GUID type for all the partitions from boot <--> inactive, etc and rewriting structures in /misc. If you have A/B and you wrote some random /misc, that could be the problem. I don't have A/B so I can erase /misc without a problem. Don't you do that!

Did TWRP maybe do an update on you?

You should be able to boot to recovery from EDL. I've never had success booting to fastboot from EDL. It seems to ignore "bootonce-bootloader". Since you have A/B you have to be careful screwing around with /misc. You can pull one "sector" (i.e. 4096 bytes) of misc and then hex edit the very start to read "boot-recovery". Then write it back and tell EDL to reboot.

nonex · 05-14-2022, 02:07 PM

This was really great advice! Thank you!!

I hex-edited misc and got into recovery. There I selected fastboot and set the active slot to b. Now everything is working again.

Btw. I also tried manually sideloading the decrypted update.zip, but it was incompatible, because device-type "NovaAirC" was excepted, but it got "BOOX". But I guess I don't need to bother if it is working now...

05-13-2022, 04:52 PM	#1
nonex Junior Member Posts: 3 Karma: 10 Join Date: May 2022 Device: NovaAirC	Unbrick Nova Air C Hi everyone, I wanted to experiment a bit and tried using a custom TWRP recovery on my Nova Air C. After doing a fastboot flash recovery twrp.img and fastboot boot twrp.img (following the wrong instructions) I am stuck in the bootloader, unable to enter either recovery or fastboot. With an edl-cable I got a copy of my partitions. But I have no working image I could flash in edl-mode. Does anybody know what else to do or could provide a working boot.img?

05-14-2022, 03:50 AM	#3
nonex Junior Member Posts: 3 Karma: 10 Join Date: May 2022 Device: NovaAirC	Thanks for the link. I decrypted the upx file, and dumped the partitions inside payload.bin. I tried flashing on both a and b partitions, but this unfortunately did not fix the issue. I also tried flashing all partitions inside. (aside from system, vendor and product, because I don't see those partitions.) I noticed, that the boot.img of the update is the same as my boot_b, but all the a-Partitions are marked as active. Maybe It would help, if I can set the b-partition as active? The Python edl-tool has that option but it does not seem to be working. When calling "edl --loader=662.elf setactiveslot b" I got: Code: firehose - [LIB]: Error:['INFO: Calling handler for patch', 'ERROR: patch size too large 128'] Do you have any more ideas?

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05-13-2022, 05:26 PM	#2
Renate Onyx-maniac Posts: 3,193 Karma: 12537601 Join Date: Feb 2012 Device: Nook NST, Glow2, 3, 4, '21, Kobo Aura2, Poke3, Poke5, Go6	Get the 3.2.2 update. Decrypt it with DeBooxUpd.py (Google it). Extract boot.img Flash it. http://firmware-us.boox.com/fbddd5e0...cbc/update.upx MD5 = fbddd5e0b6de5d32f2111d6177619cbc Onyx/NovaAirC/NovaAirC:11/2022-04-23_15-11_3.2.2_559727551f/32979:user/dev-keys

05-14-2022, 07:02 AM	#4
Renate Onyx-maniac Posts: 3,193 Karma: 12537601 Join Date: Feb 2012 Device: Nook NST, Glow2, 3, 4, '21, Kobo Aura2, Poke3, Poke5, Go6	Oops, I misread what you said. I thought that you had flashed TWRP to both recovery and boot. Theoretically flashing boot with boot.img from the update shouldn't be a problem. It's unfortunate that "boot" is used in different contexts, it breeds confusion. You can "fastboot flash" an image or you can "fastboot boot" an image, they are a bit unrelated. The "gold standard" is writing an image to a partition (using edl, fastboot or adb dd) then doing a reset. I've seen lots of cases (which I couldn't nail down) where "fastboot boot" doesn't start up correctly, probably because of cmdline getting confused? In many cases "fastboot boot" does work and if it does it's an easy way to try out an image without writing anything to flash. If you do hit problems it's worth trying with the "gold standard". Don't go crazy flashing things. You might be digging yourself a bigger hole. Some people have had problems where the only thing that changed was the A/B slot somehow. Fastboot can also flip A/B and I would trust that a bit more than the Python EDL. The process involves relabling the GUID type for all the partitions from boot <--> inactive, etc and rewriting structures in /misc. If you have A/B and you wrote some random /misc, that could be the problem. I don't have A/B so I can erase /misc without a problem. Don't you do that! Did TWRP maybe do an update on you? You should be able to boot to recovery from EDL. I've never had success booting to fastboot from EDL. It seems to ignore "bootonce-bootloader". Since you have A/B you have to be careful screwing around with /misc. You can pull one "sector" (i.e. 4096 bytes) of misc and then hex edit the very start to read "boot-recovery". Then write it back and tell EDL to reboot.

05-14-2022, 02:07 PM	#5
nonex Junior Member Posts: 3 Karma: 10 Join Date: May 2022 Device: NovaAirC	This was really great advice! Thank you!! I hex-edited misc and got into recovery. There I selected fastboot and set the active slot to b. Now everything is working again. Btw. I also tried manually sideloading the decrypted update.zip, but it was incompatible, because device-type "NovaAirC" was excepted, but it got "BOOX". But I guess I don't need to bother if it is working now...

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