MMDVM setup on a Pi

This is intended mostly as an aide-memoir to myself – your mileage may vary!

Image the Pi's SD card with Raspbian.
Mount the boot partition and edit cmdline.txt
- Remove console=serial0,115200
- Save
Edit config.txt and add the following to the end of the file:
```
enable_uart=1
dtoverlay=pi3-disable-bt
```
- This disables the Bluetooth module and enables the UART for MMDVM use.
Unmount the partitions and fit the SD card to the Pi – do not fit the MMDVM POG board yet!
Boot the Pi
When the Pi boots, log in (username pi, password raspberry)

Enter the following commands:

sudo systemctl disable serial-getty@ttyAMA0.service
sudo systemctl disable hciuart

Shut down the Pi and install the MMDVM POG board. Note: remove the 3.3V regulator if you're using the POG board as a HAT!
Boot the Pi and install the MMDVM software.