blackknobs/src/main.rs

#![no_std]
#![no_main]

use panic_semihosting as _;
use rtic::app;
use systick_monotonic::*;
use stm32f1xx_hal::{
    adc,
    dma,
    pac::ADC1,
    prelude::*,
    gpio::{self, Analog},
    serial::{Config, Serial},
};
use embedded_midi::{self, MidiMessage};

const CONTROL_CNT: usize = 9;

// Concrete midi out type alias
type MidiOut = embedded_midi::MidiOut<
    stm32f1xx_hal::serial::Tx<
        stm32f1xx_hal::pac::USART1
    >
>;

// Adc channels to scan
pub struct AdcPins(
    gpio::gpioa::PA0<Analog>,
    gpio::gpioa::PA1<Analog>,
    gpio::gpioa::PA2<Analog>,
    gpio::gpioa::PA3<Analog>,
    gpio::gpioa::PA4<Analog>,
    gpio::gpioa::PA5<Analog>,
    gpio::gpioa::PA6<Analog>,
    gpio::gpioa::PA7<Analog>,
    gpio::gpiob::PB0<Analog>,
);

impl adc::SetChannels<AdcPins> for adc::Adc<ADC1>
{
    fn set_samples(&mut self) {
        for ch in 0..(CONTROL_CNT + 1) as u8 {
            self.set_channel_sample_time(ch, adc::SampleTime::T_28);
        }
    }
    fn set_sequence(&mut self) {
        self.set_regular_sequence(&[0, 1, 2, 3, 4, 5, 6, 7, 8]);
        //self.set_continuous_mode(true);
    }
}

// San DMA recources, cunsumed by the DMA controller
pub struct ScanDmaResources(
    adc::Adc<ADC1>,
    AdcPins,
    dma::dma1::C1,
);

#[derive(Copy, Clone)]
pub struct MidiControl{
    value: u8, // Actually a 7 bit value
    update: bool,
}

#[app(
    device = stm32f1xx_hal::pac,
    peripherals = true,
    dispatchers = [SPI1]
)]
mod app {
    use super::*;

    #[shared]
    struct Shared {
        controls: [MidiControl; 9],
    }

    #[local]
    struct Local {
        dma_buffer:  Option<&'static mut [u16; CONTROL_CNT]>,
        scan_dma_rescources: Option<ScanDmaResources>,
        midi_out: MidiOut,
    }

    #[monotonic(priority = 1, binds = SysTick, default = true)]
    type MonoTimer = Systick<1000>;

    #[init(local = [buffer: [u16; CONTROL_CNT] = [0u16; CONTROL_CNT]])]
    fn init(cx: init::Context) -> (Shared, Local, init::Monotonics) {

        let mut flash = cx.device.FLASH.constrain();
        let rcc = cx.device.RCC.constrain();

        let clocks = rcc
                     .cfgr
                     .use_hse(8.MHz())
                     .sysclk(48.MHz())
                     .adcclk(2.MHz())
                     .freeze(&mut flash.acr);
 
        let mono = Systick::new(cx.core.SYST, 48_000_000);

        let mut afio = cx.device.AFIO.constrain();

        let mut gpioa = cx.device.GPIOA.split();
        let tx = gpioa.pa9.into_alternate_open_drain(&mut gpioa.crh);
        let rx = gpioa.pa10;

        let usart = Serial::new(
            cx.device.USART1,
            (tx, rx),
            &mut afio.mapr,
            Config::default().baudrate(31250.bps()).parity_none(),
            &clocks,
        );

        let mut gpiob = cx.device.GPIOB.split();

        // SPI 2, PB13, PB15
        let adc_pins = AdcPins(
            gpioa.pa0.into_analog(&mut gpioa.crl),
            gpioa.pa1.into_analog(&mut gpioa.crl),
            gpioa.pa2.into_analog(&mut gpioa.crl),
            gpioa.pa3.into_analog(&mut gpioa.crl),
            gpioa.pa4.into_analog(&mut gpioa.crl),
            gpioa.pa5.into_analog(&mut gpioa.crl),
            gpioa.pa6.into_analog(&mut gpioa.crl),
            gpioa.pa7.into_analog(&mut gpioa.crl),
            gpiob.pb0.into_analog(&mut gpiob.crl),
        );
        let adc1 = adc::Adc::adc1(cx.device.ADC1, clocks);
        let dma_ch1 = cx.device.DMA1.split().1;

        let scan_dma_rescources = ScanDmaResources(adc1, adc_pins, dma_ch1);

        let (tx, _rx) = usart.split();
        let midi_out = MidiOut::new(tx);

        read_adc::spawn().unwrap();

        (
            Shared {
                controls: [
                    MidiControl { value: 0, update: false };
                    CONTROL_CNT
                ],
            },
            Local {
                dma_buffer: Some(cx.local.buffer),
                scan_dma_rescources: Some(scan_dma_rescources),
                midi_out,
            },
            init::Monotonics(mono)
        )
    }

    // This can be implemented non-blocking (use the DMA1 interrupt)
    // Is it worth the effort?
    #[task(local = [scan_dma_rescources, dma_buffer], shared = [controls])]
    fn read_adc(mut cx: read_adc::Context) {
        let resources = cx.local.scan_dma_rescources;
        let ScanDmaResources(adc, pins, dma) = resources.take().unwrap();
        let adc_scan = adc.with_scan_dma(pins, dma);
        // Get DMA buffer
        let buffer = cx.local.dma_buffer.take().unwrap();
        // Perform read
        let (buffer, adc_scan) = adc_scan.read(buffer).wait();
        // Put the recources back in place
        let (adc, pins, dma) = adc_scan.split();
        resources.replace(ScanDmaResources(adc, pins, dma));
        // Convert adc values to midi control values and check if they changed
        cx.shared.controls.lock(|controls| {
            for i in 0..controls.len() {
                let value = adc_to_midi(&buffer[i]);
                if controls[i].value != value {
                    controls[i].value = value;
                    controls[i].update = true;
                }
            }
        });
        // Put the buffer back in place
        cx.local.dma_buffer.replace(buffer);

        send_control_changes::spawn().unwrap();
    }

    #[task(local = [midi_out], shared = [controls])]
    fn send_control_changes(mut cx: send_control_changes::Context) {
        cx.shared.controls.lock(|controls| {
            for i in 0..controls.len() {
                if controls[i].update {
                    let event = MidiMessage::ControlChange(
                        0u8.into(),
                        (i as u8).into(),
                        controls[i].value.into()
                    );
                    cx.local.midi_out.write(&event).unwrap();
                    controls[i].update = false;
                }
            }
        });
        read_adc::spawn_after(systick_monotonic::ExtU64::millis(100)).unwrap();
    }
}

// Converts a 12 bit adc value to a 7 bit midi control value
fn adc_to_midi(adc_val: &u16) -> u8{
    ((adc_val & 0x0FFF) >> 5) as u8
}