All you need to know about how to setup an OpenThread Border Router using a Raspberry Pi 4 and the nRF52840 USB Dongle
In order to open up the Thread network we need a IEEE802.15.4 transceiver. OTBR supports a 15.4 radio chip in Radio Co-Processor (RCP) mode. In this mode, the OpenThread stack is running on the host side and transmits/receives frames over the IEEE802.15.4 transceiver. The nRF52840 USB Dongle can do just that for us!
Go to the ot-nrf528xx repo clone it and follow the OpenThread on nRF52840 Example
git clone https://github.com/openthread/ot-nrf528xx.git
cd ot-nrf528xx
git submodule update --init
./script/bootstrap
./script/build nrf52840 USB_trans -DOT_COMMISSIONER=ON -DOT_THREAD_VERSION=1.3 -DOT_BOOTLOADER=USB
arm-none-eabi-objcopy -O ihex build/bin/ot-rcp ot-rcp.hex
Attention: we will need the RCP firmware for the raspberry pi.
You can go and follow this OpenThread Guide - I will just summarise it here.
Install raspios-buster-armhf-lite onto your Raspberry Pi 4. The guide recommends this version I am not sure if it will also run with a plain Raspberry OS.
git clone https://github.com/openthread/ot-br-posix.git --depth 1
cd ot-br-posix
./script/bootstrap
INFRA_IF_NAME=wlan0 ./script/setup
once this is working stick in the nRF52840 stick and restart the service sudo service otbr-agent restart