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    Booting from the X820 / X850 - Optional X820 / X850     
     
  This tutorial explains how to boot your Raspberry Pi 3 from the X820 V3.0.

Program USB Boot Mode


Before a Raspberry Pi 3 will boot from the X820 v3.0, it needs to be booted from an SD card with a config option to enable USB boot mode. This will set a bit in the OTP (One Time Programmable) memory in the Raspberry Pi SoC that will enable booting from the X820 v3.0. Once this bit has been set, the SD card is no longer required. Note that any change you make to the OTP is permanent and cannot be undone.

You can use any SD card running Raspbian or Raspbian Lite to program the OTP bit. If you don't have such an SD card then you can install Raspbian or Raspbian Lite in the normal way - see installing images.

First, prepare the /boot directory with up to date boot files:
 
$ sudo apt-get update && sudo apt-get upgrade

The above step is not required if you use the 2017-04-10 release of Raspbian / Raspbian Lite or later.

Then enable USB boot mode with this code:
echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt


This adds program_usb_boot_mode=1 to the end of /boot/config.txt. Reboot the Raspberry Pi with sudo reboot, then check that the OTP has been programmed with:

$ vcgencmd otp_dump | grep 17:
17:3020000a

Ensure the output 0x3020000a is shown. If it is not, then the OTP bit has not been successfully programmed.

If you wish, you can remove the program_usb_boot_mode line from config.txt, so that if you put the SD card in another Raspberry Pi, it won't program USB boot mode. Make sure there is no blank line at the end of config.txt. You can edit config.txt using the nano editor using the command

sudo nano /boot/config.txt, for example.

Prepare the operating system image

Starting with the 2017-04-10 release of Raspbian you can install a working Raspbian system to the X820 by copying the operating system image directly onto it, in the same way that you would for an SD card. To perform this step, follow the instructions here, remembering to select the drive that corresponds to your X820 mass storage device.

Once you have finished imaging your X820, remove the USB data cable from your computer and insert the USB bridge into your Raspberry Pi and X820 USB ports.

Boot your Raspberry Pi 3 from the USB mass storage device

Powering it up. After between five and ten seconds the Raspberry Pi should begin booting, and display the rainbow splash screen on an attached screen.



 
     
 
       
 
     
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