This is a research project into embedded development in Rust.
The goal is to create a simple serial link between two BBC micro:bit v1 devices over 2.4 GHz radio. This would enable for example a PPP connection between two locations over a distance of a few tens of metres.
micro:bit v1 has an nRF51822 microcontroller, which features UART and a 2.4 GHz radio with a pretty low-level API. Here's a diagram of the setup:
ppp client <------> micro:bit ~~~~~~~ micro:bit <------> ppp client
serial radio serial
- The serial over radio link is working, and
pppdcan be used to establish a connection over the link. - Currently uses 38400 baud rate. Higher baud rates may be possible, but there's a limit to how fast the firmware can read and write data to the UART peripheral.
- Sends XON/XOFF flow control commands to avoid overflowing buffers in the receiving side, so XON/XOFF has to be
configured in
pppd.
Here's an example pppd command. The same commmand can be used on both ends of the link, just swap the IP addresses.
/dev/DEVICE is the serial device connected to the micro:bit.
$ pppd local nodetach noauth nolock noccp xonxoff asyncmap a0000 LOCAL-IP:REMOTE-IP /dev/DEVICE 38400
Install prerequisites
rustup target add thumbv6m-none-eabi
cargo install flip-link
cargo install probe-rs --features cli
Build and flash the firmware:
cargo run
To receive debug logging from the device, set the DEFMT_LOG environment variable:
DEFMT_LOG=debug cargo run
Currently uses pins 0 and 1 of the edge connector for UART RX and TX.