f3 0.4.1

//! Sharing memory using a `Resource`
//!
//! This builds on top of the `concurrent` example. The `loopback` task now
//! additionally parses the received data as a command. Three commands are
//! available:
//!
//! - `reverse` - reverses the spin direction of the LED roulette
//! - `bounce` - puts the roulette in *bounce* mode where it reverses its spin
//!   direction every time it completes one turn.
//! - `continuous` - puts the roulette in *continuous* mode where it keeps
//!   spinning in the same direction.

#![feature(const_fn)]
#![feature(used)]
#![no_std]

// version = "0.2.2", default-features = false
extern crate cast;

// version = "0.2.0"
extern crate cortex_m_rt;

// version = "0.1.0"
#[macro_use]
extern crate cortex_m_rtfm as rtfm;

extern crate f3;

// version = "0.1.0"
extern crate heapless;

use core::cell::Cell;

use cast::{u8, usize};
use f3::led::{self, LEDS};
use f3::serial::Serial;
use f3::stm32f30x::interrupt::{Tim7, Usart1Exti25};
use f3::stm32f30x;
use f3::timer::Timer;
use heapless::Vec;
use rtfm::{C1, Local, P0, P1, Resource, T0, T1, TMax};

// SUPPORT CODE
struct State {
    direction: Cell<Direction>,
    mode: Cell<Mode>,
}

impl State {
    const fn new() -> Self {
        State {
            direction: Cell::new(Direction::Clockwise),
            mode: Cell::new(Mode::Continuous),
        }
    }
}

#[derive(Clone, Copy)]
enum Direction {
    Clockwise,
    Counterclockwise,
}

impl Direction {
    fn reverse(self) -> Self {
        match self {
            Direction::Clockwise => Direction::Counterclockwise,
            Direction::Counterclockwise => Direction::Clockwise,
        }
    }
}

#[derive(Clone, Copy, PartialEq)]
enum Mode {
    Bounce,
    Continuous,
}

// CONFIGURATION
pub const BAUD_RATE: u32 = 115_200; // bits per second
const FREQUENCY: u32 = 4; // Hz

// RESOURCES
peripherals!(stm32f30x, {
    GPIOA: Peripheral {
        register_block: Gpioa,
        ceiling: C0,
    },
    GPIOE: Peripheral {
        register_block: Gpioe,
        ceiling: C0,
    },
    RCC: Peripheral {
        register_block: Rcc,
        ceiling: C0,
    },
    TIM7: Peripheral {
        register_block: Tim7,
        ceiling: C1,
    },
    USART1: Peripheral {
        register_block: Usart1,
        ceiling: C1,
    },
});

static SHARED: Resource<State, C1> = Resource::new(State::new());

// INITIALIZATION PHASE
fn init(ref priority: P0, threshold: &TMax) {
    let gpioa = GPIOA.access(priority, threshold);
    let gpioe = GPIOE.access(priority, threshold);
    let rcc = RCC.access(priority, threshold);
    let tim7 = TIM7.access(priority, threshold);
    let timer = Timer(&tim7);
    let usart1 = USART1.access(priority, threshold);

    led::init(&gpioe, &rcc);
    timer.init(&rcc, FREQUENCY);
    Serial(&usart1).init(&gpioa, &rcc, BAUD_RATE);

    timer.resume();
}

// IDLE LOOP
fn idle(_priority: P0, _threshold: T0) -> ! {
    // Sleep
    loop {
        rtfm::wfi();
    }
}

// TASKS
tasks!(stm32f30x, {
    roulette: Task {
        interrupt: Tim7,
        priority: P1,
        enabled: true,
    },
    receive: Task {
        interrupt: Usart1Exti25,
        priority: P1,
        enabled: true,
    },
});

fn receive(mut task: Usart1Exti25, ref priority: P1, ref threshold: T1) {
    // 16 byte buffer
    static BUFFER: Local<Vec<u8, [u8; 16]>, Usart1Exti25> = {
        Local::new(Vec::new([0; 16]))
    };

    let usart1 = USART1.access(priority, threshold);
    let serial = Serial(&usart1);

    if let Ok(byte) = serial.read() {
        if serial.write(byte).is_err() {
            // As we are echoing the bytes as soon as they arrive, it should
            // be impossible to have a TX buffer overrun
            #[cfg(debug_assertions)]
            unreachable!()
        }

        let buffer = BUFFER.borrow_mut(&mut task);

        if byte == b'\r' {
            // end of command

            let shared = SHARED.access(priority, threshold);
            match &**buffer {
                b"bounce" => shared.mode.set(Mode::Bounce),
                b"continuous" => shared.mode.set(Mode::Continuous),
                b"reverse" => {
                    shared.direction.set(shared.direction.get().reverse());
                }
                _ => {}
            }

            // clear the buffer to prepare for the next command
            buffer.clear();
        } else {
            // push the byte into the buffer

            if buffer.push(byte).is_err() {
                // error: buffer full
                // KISS: we just clear the buffer when it gets full
                buffer.clear();
            }
        }
    } else {
        // Only reachable through `rtfm::request(receive)`
        #[cfg(debug_assertions)]
        unreachable!()
    }
}

fn roulette(mut task: Tim7, ref priority: P1, ref threshold: T1) {
    static STATE: Local<u8, Tim7> = Local::new(0);

    let tim7 = TIM7.access(priority, threshold);
    let timer = Timer(&tim7);

    if timer.clear_update_flag().is_ok() {
        let state = STATE.borrow_mut(&mut task);
        let curr = *state;

        let shared = SHARED.access(priority, threshold);
        let mut direction = shared.direction.get();

        if curr == 0 && shared.mode.get() == Mode::Bounce {
            direction = direction.reverse();
            shared.direction.set(direction);
        }

        let n = u8(LEDS.len()).unwrap();
        let next = match direction {
            Direction::Clockwise => (curr + 1) % n,
            Direction::Counterclockwise => curr.checked_sub(1).unwrap_or(n - 1),
        };

        LEDS[usize(curr)].off();
        LEDS[usize(next)].on();

        *state = next;
    } else {
        // Only reachable through `rtfm::request(roulette)`
        #[cfg(debug_assertion)]
        unreachable!()
    }
}