[FAQ] Rooting with FlashCast Mini-FAQ

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By bhiga, Recognized Contributor on 29th January 2014, 11:11 PM
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This mini-FAQ is intended to avoid clutter in the FlashCast thread.

If you have specific questions/comments/suggestions for FlashCast itself or its developer, or want to get the newest FlashCast, please use the main FlashCast thread.

Likewise, if you have questions/comments/suggestions for Eureka-ROM, its developers, or want to get the newest Eureka-ROM, please use the main Eureka-ROM thread.

The HubCap exploit has been patched in firmware build 19084. This means yet again, only certain Chromecasts can have root. It didn't take long - only about a month from the exploit's release and 2-3 weeks from the source release before a patch arrived.

If your Chromecast is on firmware build 19084 or newer, it is not rootable.

Available root methods depend on what firmware your Chromecast is running:
  1. Original build 12072 (old US released Chromecasts only - see Rootable Serial Numbers thread for guidance)
    Hardware requirements:
    • Powered USB OTG cable
    • USB flash drive 256MB or larger
    Instructions: Continue reading below, past this list
    If you really want to, you can use the HubCap root below instead, but it's fewer parts to try the original FlashCast method first.
  2. Build earlier than 19084 (newer US release Chromecasts and all international release Chromecasts)
    Hardware requirements:
    • real (does not work through hubs!) powered USB OTG cable
    • USB flash drive 1GB or larger
    • Teensy 2.0 or 2.0++ development board
    • USB A to Mini B cable (to connect Teensy to PC)
    Instructions: Stop reading this thread. Go to HubCap thread for instructions.

The information below pertains to the original FlashCast root method for Chromecasts with the original 12072 bootloader.

First, understand how FlashCast works, and when it doesn't...
FlashCast is not really a "root tool" but rather a ROM/mod flashing utility, similar to CWM or TWRP recoveries in the phone/tablet realm. Thus, "rooting a Chromecast with FlashCast" really means flashing a rooted ROM image using FlashCast.
Currently, FlashCast will only run on Chromecasts that have the original build 12072 bootloader.
Newer Chromecasts shipped from the factory with newer bootloaders, so except for rare exceptions, only initial-release Chromecast units came with build 12072.
The serial number provides a reasonable guess at the build on an unopened, unused Chromecast - see the Rootable Serial Numbers thread
To further complicate matters, Chromecast automatically updates itself once set up, so even if you have a serial number in the range, if it has been set up with Internet access, most likely it has already been updated and FlashCast won't work on it. It is safe to try FlashCast even if you don't think your Chromecast has root potential - either FlashCast will run and you have the option to flash a rooted ROM, or it won't and you don't have root potential.

Second, check the flowcharts for First boot of a newly-prepared FlashCast stick and Flashing Eureka-ROM with FlashCast USB stick
Remember, you need a powered USB OTG cable - it needs to provide power to the OTG host (upstream, not just to OTG devices) as Chromecast needs power to operate.

REMEMBER: For a just-written or re-written FlashCast USB stick, the first boot with it does not root your Chromecast, because it does not write a ROM (which is what preserves root) until the second round, after you load the onto the stick. If you haven't put a onto the FlashCast USB stick, you have not applied a ROM yet and you are still at risk of losing root (unless you're just applying a mod or new ROM over an existing root-preserving ROM).

If you need to know why you should or shouldn't root, and why you need to decide before you start using Chromecast, check Root Mini-FAQ: What's the big deal with root?

Use of wall (utility) power is highly recommended for flashing - TV USB ports, USB power packs, and other uncontrolled or potentially-non-constant power sources can cause problems if they turn off or give out in the middle of a flash.

If you run into trouble, see below.
  1. FlashCast doesn't show up at all.
    Your Chromecast is not rootable, your OTG cable is miswired or defective, your USB stick was not imaged properly, or your USB stick is not compatible.
    See these:
    Piecing OTG together with Y-cable and adapter
    Long thread on OTG piecemeal workarounds
    on proper OTG wiring/assembly if you aren't using an assembled powered OTG cable.

    Here are tips for potentially writing the FlashCast image from your Android device, though using a computer is still recommended.

  2. FlashCast shows up but only get red LED on Chromecast
    FlashCast did not find your, it is corrupt, or your USB stick has errors
    Windows users - make 100% sure that your file is named exactly not
    By default, Windows hides file extensions and this can cause misnamed files.
    See this explanatory image

    Also check your OTG cable - a flakey OTG cable can let FlashCast start but fail to flash too. See previous links for OTG cable assembly guidance.

  3. FlashCast shows up, the LED is white, but all I see is the line of dots after the reboot
    Check that the button on the Chromecast is not stuck down. On some units the plastic button-pusher can get wedged down. Gently but firmly push the button all the way down and wiggle it on release. If that doesn't work, try flicking the button to dislodge it.

  4. I reached "Sorry, your Chromecast is not rootable" in the flowchart.
    Try the HubCap exploit.
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Last edited by bhiga; 6th September 2014 at 04:15 PM. Reason: HubCap patched in build 19084
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