servo-pio

Control servo motors using the RP2040's PIO peripheral.

Example

See work_in_progress.rs for a complete example with a Pimoroni Servo2040. Below you'll find the details relevant for this crate.

#[bsp::entry]
fn main() -> ! {
    // ... general setup ...

    let pins = bsp::Pins::new(
        pac.IO_BANK0,
        pac.PADS_BANK0,
        sio.gpio_bank0,
        &mut pac.RESETS,
    );
    let servo_pins: [_; NUM_SERVOS] = [
        ServoData {
            pin: pins
                .servo3
                .reconfigure::<FunctionPio0, PullNone>()
                .into_dyn_pin(),
            calibration: Calibration::builder(AngularCalibration::default())
                .limit_lower()
                .limit_upper()
                .build(),
        },
        ServoData {
            pin: pins
                .servo4
                .reconfigure::<FunctionPio0, PullNone>()
                .into_dyn_pin(),
            calibration: Calibration::builder(AngularCalibration::default())
                .limit_lower()
                .limit_upper()
                .build(),
        },
        ServoData {
            pin: pins
                .servo5
                .reconfigure::<FunctionPio0, PullNone>()
                .into_dyn_pin(),
            calibration: Calibration::builder(AngularCalibration::default())
                .limit_lower()
                .limit_upper()
                .build(),
        },
        ServoData {
            pin: pins
                .servo6
                .reconfigure::<FunctionPio0, PullNone>()
                .into_dyn_pin(),
            calibration: Calibration::builder(AngularCalibration::default())
                .limit_lower()
                .limit_upper()
                .build(),
        },
    ];

    let (mut pio0, sm0, _, _, _) = pac.PIO0.split(&mut pac.RESETS);
    // Use a different pio for the leds because they run at a different
    // clock speed.
    let (mut pio1, sm10, _, _, _) = pac.PIO1.split(&mut pac.RESETS);
    let dma = pac.DMA.split(&mut pac.RESETS);

    // Configure the Timer peripheral in count-down mode.
    let timer = hal::Timer::new(pac.TIMER, &mut pac.RESETS, &clocks);
    let mut count_down = timer.count_down();

    // Build the servo cluster
    let mut servo_cluster = match build_servo_cluster(
        &mut pio0,
        sm0,
        (dma.ch0, dma.ch1),
        servo_pins,
        #[cfg(feature = "debug_pio")]
        pins.scl
            .reconfigure::<FunctionPio0, PullNone>()
            .into_dyn_pin(),
        clocks.system_clock,
        unsafe { &mut STATE1 },
    ) {
        Ok(cluster) => cluster,
        Err(e) => {
            defmt::error!("Failed to build servo cluster: {:?}", e);
            #[allow(clippy::empty_loop)]
            loop {}
        }
    };

    // Unmask the DMA interrupt so the handler can start running. This can only
    // be done after the servo cluster has been built.
    unsafe {
        pac::NVIC::unmask(pac::Interrupt::DMA_IRQ_0);
    }

    const MIN_PULSE: f32 = 1500.0;
    const MID_PULSE: f32 = 2000.0;
    const MAX_PULSE: f32 = 2500.0;
    let movement_delay = 20.millis();

    // We need to use the indices provided by the cluster because the servo pin
    // numbers do not line up with the indices in the clusters and PIO.
    let [servo1, servo2, servo3, servo4] = servo_cluster.servos();

    servo_cluster.set_pulse(servo1, MAX_PULSE, false);
    servo_cluster.set_pulse(servo2, MID_PULSE, false);
    servo_cluster.set_pulse(servo3, MIN_PULSE, false);
    servo_cluster.set_value(servo4, 35.0, true);
    count_down.start(movement_delay * 5);

    let mut velocity1: f32 = 10.0;
    let mut velocity2: f32 = 15.0;
    let mut velocity3: f32 = 25.0;
    let mut velocity4: f32 = 50.0;
    #[allow(clippy::empty_loop)]
    loop {
        for (servo, velocity) in [
            (servo1, &mut velocity1),
            (servo2, &mut velocity2),
            (servo3, &mut velocity3),
            (servo4, &mut velocity4),
        ] {
            let mut pulse = servo_cluster.pulse(servo).unwrap();
            pulse += *velocity;
            if !(MIN_PULSE..=MAX_PULSE).contains(&pulse) {
                *velocity *= -1.0;
                pulse = pulse.clamp(MIN_PULSE, MAX_PULSE);
            }
            // Assign pulses to each servo, but passing `false` to prevent
            // immediate usage of the pulse.
            servo_cluster.set_pulse(servo, pulse, false);
        }
        // Load to trigger a simultaneous of the values to the servos. Phasing
        // of the PWM signals will be used to prevent voltage spikes.
        servo_cluster.load();
        count_down.start(movement_delay);
        let _ = nb::block!(count_down.wait());
    }
}

fn build_servo_cluster<C1, C2, P, SM>(
    pio: &mut PIO<P>,
    sm: UninitStateMachine<(P, SM)>,
    dma_channels: (Channel<C1>, Channel<C2>),
    servo_data: [ServoData<AngularCalibration, FunctionPio0>; NUM_SERVOS],
    #[cfg(feature = "debug_pio")] side_set_pin: Pin<DynPinId, FunctionPio0, PullNone>,
    system_clock: SystemClock,
    state: &'static mut Option<GlobalState<C1, C2, P, SM>>,
) -> Result<ServoCluster<NUM_SERVOS, P, SM, AngularCalibration>, BuildError>
where
    C1: ChannelIndex,
    C2: ChannelIndex,
    P: PIOExt<PinFunction = FunctionPio0>,
    SM: StateMachineIndex,
{
    #[allow(unused_mut)]
    let mut builder: ServoClusterBuilder<
        '_,
        AngularCalibration,
        C1,
        C2,
        P,
        SM,
        FunctionPio0,
        NUM_SERVOS,
        NUM_CHANNELS,
    > = ServoCluster::<NUM_SERVOS, P, SM, AngularCalibration>::builder(
        pio,
        sm,
        dma_channels,
        unsafe { &mut GLOBALS },
    )
    .pins_and_calibration(servo_data);
    #[cfg(feature = "debug_pio")]
    {
        builder = builder.side_set_pin(side_set_pin);
    }
    builder
        .pwm_frequency(50.0)
        .build(&system_clock, state)
        .map_err(BuildError::Build)
}

#[interrupt]
fn DMA_IRQ_0() {
    critical_section::with(|_| {
        // Safety: we're within a critical section, so nothing else will modify global_state.
        dma_interrupt(unsafe { &mut GLOBALS });
    });
}

Contributing

Contributions are what make the open source community such an amazing place to be learn, inspire, and create. Any contributions you make are greatly appreciated.

The steps are:

1. Fork the Project by clicking the 'Fork' button at the top of the page.
2. Create your Feature Branch (git checkout -b feature/AmazingFeature)
3. Make some changes to the code or documentation.
4. Commit your Changes (git commit -m 'Add some AmazingFeature')
5. Push to the Feature Branch (git push origin feature/AmazingFeature)
6. Create a New Pull Request
7. An admin will review the Pull Request and discuss any changes that may be required.
8. Once everyone is happy, the Pull Request can be merged by an admin, and your work is part of our project!

Code of Conduct

Contribution to this crate is organized under the terms of the Rust Code of Conduct, and the maintainer of this crate, Paul D. Faria, promises to intervene to uphold that code of conduct.

License

The contents of this repository are dual-licensed under the MIT OR Apache 2.0 License. That means you can chose either the MIT licence or the Apache-2.0 licence when you re-use this code. See MIT or APACHE2.0 for more information on each specific licence.

Note that this code is a derivative of https://github.com/pimoroni/pimoroni-pico's servo_cluster and pwm_cluster drivers. pwm.pio comes directly from pwm_cluster.pio in Pimoroni's project. Their cose is licensed under the MIT License. See Pimoroni.MIT for more information on their license.

Any submissions to this project (e.g. as Pull Requests) must be made available under these terms.