Removing Dev Lock

Update/Notes:

• Remember, you can always go to Narnia for spare parts/testing!

• Test units are in re-flow room, ask lead if one is needed to test motherboard!

• If received back from re-flow, put brand new one in the test unit.

• ATTENTION: if c720/c740 (more common, other devices do have it happen as well) sent to dev issues, when turned on and the screen comes up blank, hit "control d" and "enter" (dev mode is just black screen, so hit normal commands)

Step by step to removing developer lock from devices NOT on a school’s network

• 1. Connect the device to wifi

  2. Log into the device with Email: trdtest2017@gmail.com and Password: Repair2017

  3. Once logged into to device go to settings and type in the search box at the top “Verified” and it should say “Enable Verified access” Uncheck it.

  4. Reboot and device should be able to boot into dev mode now.

CBFTool Usage

General Tips:

• V = 3.3v

• W = 1.8v

• Mac address is E4:BE:ED:62:82:CF

Mass Flashing usage:

• Ssh into device, current password: devhack

• Use ‘screen -ls’ to see if any screens are active. Screens will persist even without an active ssh session, and allows for headless operation.

  • If there is a screen active, it will be formatted like ‘####.pts-0.raspberrypi’

  • Type ‘screen -r ####.pts-0.raspberrypi’ to reattach to that screen.

  • If there are no active screens, simply type ‘screen’

• Inside the screen session, type ‘./CBFTool.sh’ and select the board you’ll be flashing.

• Using the fob for headless operation, the button labeled ‘SUSPEND-SW’ will attempt to program the board, and the ‘VOLUME DOWN’ button will exit the CBFTool script. This will require the user to reattach the screen and run the script again.

• The user can interpret the state of the flash based on the following LED indications:

  • Green: Flash successful, ready to attempt again or cancel

  • Orange: Currently flashing, busy

  • Green + Orange: Flash failed, ready to attempt again or cancel

Individual Board usage:

Many of the instructions are the same, but screen is not really required because you’ll most likely won’t want headless operation.

• Read connected flash using './CBFTool.sh -r filename.rom'

• Search for the gVpd or other section containing the S/N.

• The command for this outside of CBFTool is 'dhex -sa searchterm /path/to/rom/filename.rom'

• The current keyboard shortcuts for dhex are as follows:

  • Ctrl+r: Search

  • Ctrl-t: Next

  • Ctrl-]: Exit (prompt to save)

To actually change the S/N, after you've found it:

Navigating the hex value entries, typically right before and after the S/N entry there are characters with hex values with a first byte of 0. Select the value immediately after the '0*' character, and replace all of the characters with value '30' until the next character with the first byte of 0. Proceed to change all entries involving the primary S/N.

• Also, typically in the first gVpd block, there might be entries such as:

  • 'block_dev_mode.1' and 'check_enrollment.1'

  • It is wise to change the values (1, hex 31) for those entries to 0, hex value 30.

• After you've done all the editing you want, use the Exit keyboard shortcut (below) to save the modified ROM file.

  • Ctrl-]: Exit (prompt to save)

It will prompt asking you if you want to write the modified ROM to the connected flash. You will most likely want to do this, as the ROM is not fully prepared to add to the list. In the case of a mistake, the original ROM as it was read has been backed up as 'filename.rom.check'.

-To finish preparation, the device must be booted into dev mode, verify the S/N has been changed in the console:

• dump_vpd_log --force

• shutdown.

• Read the image again with './CBFTool.sh -r filename.rom'

• Move and rename the file, adding the name suffix DevGood0 with:

  • 'mv /home/pi/ROMs/read/filename.rom /home/pi/ROMs/filenameDevGood0.rom'

• The file is prepared and should now show up on the UI list as 'filename'

Image examples (In Order Steps)

Possible Warnings/errors