Help CM12 boot loop with no recovery and no download mode. Toast?

[Android Question]

I just switched to CM12 nightlies on a Sprint Note 3 and regret it immensely. The CM downloader app updated me successfully three times, but the new version today threw me into a boot loop at the "optimizing apps" stage. Right after optimization, it restarts instead of entering the OS. TWRP and download modes are completely non-responsive. I have left the phone off for hours and tried each 100 times.

I have ADB working on the Mac laptop, but it cannot connect see the phone with the typical "./fastboot devices" commands. Parallels [in case I need Windows] sees a Samsung device is connected.

Every solution I have read (all day today) involves the obvious recovery mode fixes or Odin flashes, but I can't get to either. Time to shop for a new phone? Any advice is much appreciated.

 

[Hadron]

I'm not a Samsung expert, so can't advise on Odin etc. When you say TWRP and download are "non-responsive" you mean you can't get into them, or that you can but they no longer work? Have you tried pulling the battery out for a few minutes, to ensure that the system RAM is discharged, before trying?

I don't understand why a ROM update should affect either, and indeed don't understand how it can affect low-level stuff like the download mode. But yes, I'd say you need to get either recovery working or fastboot or odin talking to the phone (unless there is some other Samsung-specific trick I don't know, like how you can reflash an HTC using a signed zip file on the card from the bootloader).

 

[Grimmmmer]

Thanks for the reply; I appreciate a second opinion.

By unresponsive, I mean that the phone acts like I am not holding any volume buttons at all. It never shows anything but the standard boot flags (kernel not seandroid, ...). When the phone was off for hours, I did remove the battery to discharge the RAM.

The frustrating part is that after it finishes optimizing apps and just before the home screen arrives, it hesitates and goes back to the CM12 theme boot animation. HOWEVER, this may help expose an opportunity for some aggressive ADB command / script that can grab control at the right point in the long loop. I just don't know what that would be. Maybe there's an ADB guru out there.

Short of that, it is starting to seem like a simple CM12 nightly just fully bricked me, despite my diligent NAND backups. Lesson learned.

 

[funkylogik]

What you could try is buying an inexpensive USB Jig to try and force the phone into download mode

 

[Grimmmmer]

Fantastic. I had no idea these things existed. THANKS.

 

[funkylogik]

Good luck