## Before you start

The board boots from eMMC by default. Press the USR button at power-on to boot from the microSD card.

## Installation

1. Hold the USR button.
2. Connect USB-C power.
3. Release the USR button when the power LED comes on.

## Notes

- The SD boot selection stays until power off. Repeat steps 2 to 4 at each power-on.

## Rescue

Use this if the board does not boot after a write to eMMC.

1. Hold the USR button and connect USB-C power. The board boots the microSD card
   instead of the eMMC.
2. Rewrite the eMMC from the running system, or erase it. Identify the
   eMMC with `lsblk`; it is the `mmcblk*` device that is not the card you
   booted from:
```sh
sudo blkdiscard -f /dev/mmcblkX
```
3. Power off and remove the microSD card.