Trying to unbrick asus chromebook (Mithrax)

Support General Device Support
1

System Details

  • Device: Mithrax
  • OS: ChromeOS / Linux
  • Firmware Type: RW_LEGACY / stock

Summary of the Issue

device bricked after trying to return to stock

The issue

this device (asus chromebook vibe flip cx34) was having some power issues. It would randomly start to turn off if I plugged anything into a usb port, specifically the usbc port. Once this problem gets “triggered” it would then start to randomly shutoff(even when ports are free), up to the point where it would start to power off early and early, up to the point where it would happen right at the “bios”. I would then let it completely discharge then power it back on and refresh it a few times and the problem would be gone. After the second time i decided to go back to stock and all went great, got reminded that stock scuks so I installed linux along side it again. Well that 3rd time the issue happens again so I then though to myself well maybe lets just debug this and see if it happens on stock. I then went through the process of getting the device back to stock and mid way through the laptop shuts off, leaving me with a bricked device.

the power issue, i am not sure if it is to do with stock or RW_LEGACY, it could also be the power controller. (keep in mind this device is currently bricked) I did test if the issue was battery,cord,port.. etc. best ideas is the power controller or the firmware.

I do have myself a suzyqable, but this device still has write protection on.. so idk if using that is a option atm. I think the other option would be to get one of those probes and “‘physically” flash it.

thoughts? options?

edit: purchased flasher/probe should hopefully have an un-bricked device soon.. then to debugging the power issue, hoping the suzyqable can help me out with that part.

2

flashed it, no luck. just a black screen. before the flash the light was blinking about 11 times. now after the flash the light is back to normal.

3

went ahead and re-flashed it and verified the flash.. no luck. still refuses to power on, led lights come on, fan comes on, all for a few seconds and then powers off and repeats that process.

then again with the lights blinking 11 times, which from what ive read it is saying that its a ram issues.

I think this is where I give up on it.

4

is “VB Failed to verify RW” of interest?

5

ok how about this? the shellball image coreboot-Google_Mithrax.14505.606.0.bin is only 32MB is this normal?

6

only 32MB?

how large are you expecting. Most SPI flash chips are smaller unless used on servers. majority of Chromebooks use 16MB

7

im actively working on this right now, and I think i was flashing the wrong firmware.. currently downloading and extracting the correct one.

i was getting mithrax when it seems like it should have mithrax-isvs


version
Chip:	Nuvoton NPCX993F A.00160207
Board:	3
RO:	mithrax_v2.0.19151-c23ed89000
mithrax_14505.262.0
RW:	mithrax_v2.0.22692-2e3343ffbc
mithrax_14505.606.0
Build:	mithrax_v2.0.19151-c23ed89000 mithrax_14505.262.0
2022-10-12 22:26:59 @localhost```
8

that’s the EC firmware, which is sync’d automatically at boot. If that were a problem, the device would boot to recovery with an EC SYNC signature error.

9

yea i thought that maybe that was hinting to something. not sure what to try next if this new flash doesn’t work. been doing a bit of debugging with the suzyqable, but I don’t really know what I am looking at or what I should be looking for. i did see this RW_B: Error.

10

from your description above, it sure sounds like the device is having hardware issues, not a firmware one. If you flashed the (correct) shellball rom completely using a SuzyQ, that pretty much rules out a firmware issue

11

guess its time to call it then. zero pulse.

12

ok so I have been checking for physical shorts, bad chip etc. i cant really find anything. There is one thing of note and it is that when i plug in the suzyqable and checkout /dev/ttyUSB1 I see “!! Settings mismatch !!”. Is this normal? does this maybe suggest or give you an idea of what the issue could be.
The idea of just letting this laptop collect dust is killing me.

13

there’s no output on ttyUSB1 with the stock firmware, as it disables serial console output. no idea what would cause that or what it might mean

14

damn. anything here look of interest?
/dev/ttyUSB0
```
— UART initialized after reboot —
[Reset cause: hibernate wake-pin]
[Image: RW, 0.5.350/cr50_v0.0.13913-1a35fa3b7 tpm2:v2.0.104-f5b6842 pinweaver:v0.0.156-4ec2204 gsc-utils:v2.0.3799-0a95edcd57 2026-03-26 10:24:31 chrome-bot@chro]
[0.004501 Inits done]
0|[0.007423 init_jittery_clock_locking_optional: run level high, request to enable]
[0.029987 init took 16232]
[0.043434 update_rollback_mask: bailing out at bit 2]
[0.045558 update_rollback_mask: bailing out at bit 4]
read_tpm_nvmem: object at 0x100a not found
[0.049026 Console unlock allowed]
[0.049766 tpm_rst_asserted]
read_tpm_nvmem: object at 0x1008 not found
[0.050975 load_ec_hash error: 0x1203]
[0.051601 EC-COMM: Initialization]
[0.052135 FIPS module digest a4459b5bcbda8970…]
[0.052818 Running in FIPS 140-2 approved mode]
Console is enabled; type HELP for help.
[0.055030 AP UART on]
[0.055633 Servo disconnect]
[0.056171 EC RX only]
[0.056888 CCD state:]
[0.060535 Rdd connect]
[0.283012 CCD state: UARTEC+TX]
[0.300464 CCD state:]
[1.055374 EC on]
[1.056137 CCD EXT enable]
[1.057006 USB PHY B]
[1.057987 CCD state: UARTEC+TX I2C SPI USBEC+TX]
[1.059127 I2C connect]
[1.059646 Initialized I2C port 0, freq = 100 kHz]
[3.050365 AP off]
[6.130561 usb_reset, status 4801020]
[6.192401 usb_reset, status 9028]
[6.450317 usb_reset, status 9028]
[6.564037 usb_reset, status 1020]
[6.677444 SETAD 0x15 (21)]
```

15

also reading this section https://chromium.googlesource.com/chromiumos/platform/ec/+/fe6ca90e/docs/case_closed_debugging_cr50.md#uart-rescue-mode

UART Rescue mode

wondering if this would be the next step.