f3 0.4.0

//! Sharing memory using `Resource`
//!
//! This builds on top of the `concurrent` example. The `loopback` task now
//! additionally parses the received data as a command. Two commands are
//! available:
//!
//! - `reverse` - reverses the spin direction of the LED roulette
//! - `reset` - moves the roulette back to its start position (North)

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

// version = "0.2.0", 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::{C0, C1, C16, Local, P0, P1, Resource};

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

struct Command {
    direction: Cell<Direction>,
    reset: Cell<bool>,
}

impl Command {
    const fn new() -> Command {
        Command {
            direction: Cell::new(Direction::Clockwise),
            reset: Cell::new(false),
        }
    }
}

// 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 COMMAND: Resource<Command, C1> = Resource::new(Command::new());

// INITIALIZATION PHASE
fn init(ref prio: P0, ceil: &C16) {
    let gpioa = GPIOA.access(prio, ceil);
    let gpioe = GPIOE.access(prio, ceil);
    let rcc = RCC.access(prio, ceil);
    let tim7 = TIM7.access(prio, ceil);
    let timer = Timer(&tim7);
    let usart1 = USART1.access(prio, ceil);

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

    timer.resume();
}

// IDLE LOOP
fn idle(_prio: P0, _ceil: C0) -> ! {
    // 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 prio: P1, ref ceil: C1) {
    static BUFFER: Local<Vec<u8, [u8; 16]>, Usart1Exti25> = {
        Local::new(Vec::new([0; 16]))
    };

    let usart1 = USART1.access(prio, ceil);
    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 command = COMMAND.access(prio, ceil);
            match &**buffer {
                b"reverse" => {
                    let Command { ref direction, .. } = *command;

                    match direction.get() {
                        Direction::Clockwise => {
                            direction.set(Direction::Counterclockwise)
                        }
                        Direction::Counterclockwise => {
                            direction.set(Direction::Clockwise)
                        }
                    }
                }
                b"reset" => {
                    command.reset.set(true);
                }
                _ => {}
            }

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

fn roulette(mut task: Tim7, ref prio: P1, ref ceil: C1) {
    static STATE: Local<u8, Tim7> = Local::new(0);

    let tim7 = TIM7.access(prio, ceil);
    let timer = Timer(&tim7);

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

        let command = COMMAND.access(prio, ceil);
        let direction = command.direction.get();
        let Command { ref reset, .. } = *command;

        let n = u8(LEDS.len()).unwrap();
        let next = if reset.get() {
            reset.set(false);
            0
        } else {
            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!()
    }
}