timer.rs

#![feature(asm, lang_items, unwind_attributes, abi_avr_interrupt)]

#![no_std]
#![no_main]

extern crate arduino;

use arduino::*;
use core::ptr::write_volatile;
use core::ptr::read_volatile;

#[no_mangle]
pub extern fn main() { 
    init_timer();

    unsafe { 
        asm!("CLI");
        //asm!("SEI");
    } 

    unsafe { write_volatile(PORTB, read_volatile(PORTB) ^ PORTB5) } 
    small_delay(10000);
    unsafe { write_volatile(PORTB, read_volatile(PORTB) ^ PORTB5) } 
    small_delay(10000);
    unsafe { write_volatile(PORTB, read_volatile(PORTB) ^ PORTB5) } 

    loop { 
    } 
}

fn init_timer() { 
    const CPU_FREQUENCY_HZ: u64 = 16_000_000;
    const DESIRED_HZ_TIM1: f64 = 2.0;
    const TIM1_PRESCALER: u64 = 1024;
    const INTERRUPT_EVERY_1_HZ_1024_PRESCALER: u16 = 
        ((CPU_FREQUENCY_HZ as f64 / (DESIRED_HZ_TIM1 * TIM1_PRESCALER as f64)) as u64 - 1) as u16;

    timer1::Timer::new()
        .waveform_generation_mode(timer1::WaveformGenerationMode::ClearOnTimerMatchOutputCompare)
        .clock_source(timer1::ClockSource::Prescale1024)
        .output_compare_1(Some(INTERRUPT_EVERY_1_HZ_1024_PRESCALER))
        .configure();
}

/// A small busy loop.
fn small_delay(val: u16) { 
    for _ in 0..val { 
        unsafe { asm!("" :::: "volatile")}
    }
}

#[no_mangle]
pub unsafe extern "avr-interrupt" fn _ivr_timer1_compare_a() {
    let prev_value = read_volatile(PORTB);
    write_volatile(PORTB, prev_value ^ PINB5);
}

pub mod std {
    #[lang = "eh_personality"]
    #[no_mangle]
    pub unsafe extern "C" fn rust_eh_personality(_state: (), _exception_object: *mut (), _context: *mut ()) -> () {
    }

    #[lang = "panic_fmt"]
    #[unwind]
    pub extern fn rust_begin_panic(_msg: (), _file: &'static str, _line: u32) -> ! {
        loop { }
    }
}