Bluetooth (Linux)

The bluetooth feature connects over RFCOMM through BlueZ, the Linux Bluetooth stack, via bluer. On other operating systems, use a serial port instead.

[dependencies]
nxt-rs = { git = "https://forge.wvffle.net/wvffle/nxt-rs.git", features = ["bluetooth"] }
tokio = { version = "1", features = ["macros", "rt-multi-thread"] }

Pairing

Pair the brick once with bluetoothctl. On the brick, make sure Bluetooth is switched on and the brick is visible (Bluetooth → Visibility → Visible).

$ bluetoothctl
[bluetooth]# scan on
[NEW] Device 00:16:53:0A:0B:0C NXT
[bluetooth]# pair 00:16:53:0A:0B:0C

The brick beeps and shows a passkey prompt. The default passkey is 1234. Confirm it on the brick and enter the same passkey on the computer when asked. Finally:

[bluetooth]# trust 00:16:53:0A:0B:0C

Connecting

use nxt_rs::{Brick, transport::Bluetooth};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    for nxt in Bluetooth::paired().await? {
        println!("{} at {}", nxt.name, nxt.address);
    }

    let brick = Brick::bluetooth("00:16:53:0A:0B:0C".parse()?).await?;
    println!("battery: {}", brick.battery().await?);
    Ok(())
}

Bluetooth::paired() lists the paired devices whose Bluetooth class is that of an NXT.

Things to know

• tokio is required. bluer runs on tokio. Inside #[tokio::main] everything works. .block() starts a shared tokio runtime for you when the bluetooth feature is on.
• Latency. Each request/reply round trip takes about 60 ms, because the brick’s Bluetooth chip needs time to switch direction. Batch work into fewer commands, use send_no_reply where you don’t need an answer, or run time-critical loops on the brick and talk to it with messages.
• Default timeout: 3 seconds.
• One connection at a time. The brick accepts a single Bluetooth connection from a computer.
• The bluetooth feature is Linux-only. On Windows and macOS, use a serial port.