The intent of this library is to provide avr specific delay routines similar to the ones provided by the arduino library. The public functions are:
This crate uses the avr-config crate for fetching the CPU frequency. As such, the AVR_CPU_FREQUENCY_HZ environment variable will need to be set when compiling your crate for AVR.
Example:
export AVR_CPU_FREQUENCY_HZ=16000000
cargo build -Z build-std=core --target avr-unknown-gnu-atmega328 --releasedelay(count: u32)is a raw delay loop. Each loop is 4 cycles. The asm section can loop 65536 times. Initial overhead is about 13 cycles. Each outer loop has an overhead of about 11 cycles.
delay_us(us: u32)delay us microseconds
delay_ms(ms: u32)delay ms milliseconds
A simple example of how to use it follows.
Cargo.toml:
[package]
name = "dlyblink"
version = "0.1.0"
authors = ["John Jorgensen"]
[dependencies]
arduino = "0.1"
avr_delay = { git = "https://github.com/avr-rust/delay" }and your main.rs:
#![feature(asm, lang_items, unwind_attributes)]
#![no_std]
#![no_main]
extern crate arduino;
extern crate avr_delay;
use arduino::{DDRB, PORTB};
use core::ptr::write_volatile;
use avr_delay::{delay, delay_ms, delay_us};
#[no_mangle]
pub extern fn main() {
let mut out: u8 = 0x00;
unsafe { write_volatile(DDRB, 0xff) }
loop {
out = out ^ 0xff;
unsafe { write_volatile(PORTB, out) }
delay_ms(1000000);
}
}
// These do not need to be in a module, but we group them here for clarity.
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 { }
}
}No attempt is made to handle arithmetic overruns.
During cargo publish there could be
error: ran out of registers during register allocation
With that blocking issue is adding --no-verify considered
the lesser evil as not releasing.
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