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GSC Debug Cable / Board

Information about my GSC Debug Cables / Boards

Important

Attention buyers from outside the US, especially Canada: Depending on the country, you can save a significant amount of money on shipping if you buy outside of eBay. See the Pirate Ship Rates and Insurance Rates ($1.35). Contact my email or Chrultrabook forum account to buy.

What does it do?

This item (previously sold by SparkFun which they called SuzyQable) is for Chromebooks which support CCD (Closed Case Debugging). This item lets you communicate with the Google Security Chip inside Chromebooks, and is mainly used for disabling firmware write protect and unbricking.

How to use it to disable firmware write protect

  1. For this step, you do not need to have a debug cable plugged in. Note: After running the command, your Chromebook will return to not-developer mode, erasing all user data on your Chromebook. Run sudo gsctool -a -o. The command will say “Press PP button now!” Whenever it says that, press the power button on your Chromebook. Keep pressing the power button when needed until the command successfully completes. It will take around 3 minutes.
  2. Re-enter developer mode
  3. Plug in your USB-C cable into the debug board, orientation does not matter. Plug the debug board into the left USB-C port of your chromebook, Side A up. Plug the other end of your chromebook into a different USB port on your chromebook or into a USB port of a linux computer. On the linux computer which you plugged the cable into (which is your Chromebook if you plugged the board into your Chromebook) and run this command: watch -n 1 'lsusb | grep -E "18d1:5014|18d1:504a"'. The command will show all connected Cr50 or Ti50 USB devices every second. You should see a device called “Cr50” or “Ti50”. If you don’t, try plugging the debug board in with Side B up. If that still doesn’t work, try all other USB-C ports on your chromebook with both Side A and Side B until it works. If you’ve tried every combination then double check that your cable is working and contact me for help.
  4. Run ls /dev/ttyUSB*. It should show ttyUSB0
  5. Run sudo bash. This will switch to a root shell.
  6. Run echo "wp false" > /dev/ttyUSB0
  7. Run echo "wp false atboot" > /dev/ttyUSB0
  8. Run echo "ccd reset factory" > /dev/ttyUSB0
  9. Type exit to exit root shell
  10. Run gsctool -a -I. All flags should show “Y/Always”
  11. Run sudo crossystem wpsw_cur. It should output 0, which means firmware write protect is successfully disabled!

Versions

Cable (56k Version)

Link to buy (Out of Stock, will never be available again)

This cable was made using this guide. It uses 22k and 56k resistors. It is a home made cable.

v4.0.1

Link to buy (out of Stock, has been replaced by v4.1.0

Made using this guide

Uses 22k and 45.3k resistors. Works with USB-A male to USB-C male cables. Does not work with USB-C male to USB-C male cables.

v4.1.0

Link to buy

Made using this guide

Uses 22k and 45.3k resistors. Works with both USB-A male to USB-C male cables and USB-C male to USB-C male cables. Shield ground is connected between both USB-C components.

Contact

Email: paranjperajas@gmail.com