Module B5 - Rust for IoT

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In this module, we'll have a look at an example of a bigger Rust project.

B5 Device-host communication

The goal of this exercise is to get an idea of how code can be shared between a device and a host, in order to set up a robust communication system.

Instructions

  1. For this exercice, we'll be working in exercises/B5. There are a couple of projects in there:

    • firmware contains all code that is run on the device. Apart from what you saw in the last exercise, it contains a uarte module, which uses the PAC to enable advanced functionality not implemented by the HAL. Take a peek at the functions in there. Try not to get distracted by the implementation details, but focus on the overall functionality that is available. The main application already implements tasks to control the TimeoutUarte.
    • cli defines a simple CLI application that listens for incoming messages, and opens a rudimentary repl with which you can send commands. You'll be implementing a couple of commands yourself, so have a peek at cmd.rs, to get an idea of how to do that.
    • format contains definitions of whatever is being send from the device to the server and vice-versa. To send new commands, you'll need to update the ServerToDevice and DeviceToServer structs. If you do, don't forget to compile both the firmware and the CLI in order for getting them to communicate nicely.

  2. Flash the firmware onto the device using this command:

cd ./firmware
cargo run --release
  1. Run the CLI app with one of these commands. For <PORT> substitute the device's serial port path. If you omit the argument, the app will print any serial ports detected.
cd ./cli
cargo run -- -p <PORT>
  1. Test the setup. In the CLI repl, type
hello

Another command you can try (although it will only print stuff over RTT for now):

led 1 on

  1. Open main.rs, and look up the handle_message task. In there, incoming messages are processed. You'll find the first instructions there.

  2. Your next objective is to implement your own command. Add a command to cmd.rs in the cli package. Register it with the CommandParser::parse method, referring to the other commands in that module. Update the ServerToDevice and DeviceToServer structs in format, and handle the messages in firmware. If you need ideas, you can have the device send over accelerometer measurements whenever they're ready.

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