tangent128/holiday_lights
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WIP to fix timing on newer nightlies-

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All bits seem to register here, but with zeroes reliably becoming ones in a way that desaturates things towards white
This commit is contained in:
Tangent Wantwight 2021-07-05 01:16:22 -04:00
parent bd4de16015
commit ea8c4f00a7
1 changed files with 44 additions and 7 deletions
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51
itsybitsy_m0_lights/src/lib.rs
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@ -1,4 +1,5 @@
#![no_std]
#![feature(asm)]
extern crate cortex_m;
extern crate embedded_hal;
@ -9,6 +10,7 @@ pub use cortex_m::asm::delay;
pub use hal::entry;
use core::fmt::Debug;
use core::sync::atomic::{compiler_fence, Ordering};
use core::u8;
pub use embedded_hal::digital::v2::OutputPin;
use hal::{clock::GenericClockController, pac::Peripherals};
@ -67,14 +69,42 @@ where
{
#[inline]
pub fn write(&mut self, bit: bool) {
// go high
self.high_out.set_high().unwrap();
delay(if bit {
ONE_HIGH_CYCLES
} else {
ZERO_HIGH_CYCLES
});
unsafe {
compiler_fence(Ordering::SeqCst);
asm!(
// ? nops
"nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
);
compiler_fence(Ordering::SeqCst);
}
if bit {
unsafe {
compiler_fence(Ordering::SeqCst);
asm!(
// 7 nops
"nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
"nop;", "nop;", "nop;", "nop;",
);
compiler_fence(Ordering::SeqCst);
}
}
// go low
self.high_out.set_low().unwrap();
delay(if bit { ONE_LOW_CYCLES } else { ZERO_LOW_CYCLES });
unsafe {
compiler_fence(Ordering::SeqCst);
asm!(
// 2 nops
"nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
"nop;", "nop;", "nop;", "nop;", "nop;",
);
compiler_fence(Ordering::SeqCst);
}
}
#[inline]
@ -87,7 +117,14 @@ where
self.write(byte & 0x04 != 0);
self.write(byte & 0x02 != 0);
self.write(byte & 0x01 != 0);
delay(5);
unsafe {
compiler_fence(Ordering::SeqCst);
asm!(
// 5 nops
"nop;", "nop;", "nop;", "nop;", "nop;",
);
compiler_fence(Ordering::SeqCst);
}
}
/// Blink light, probably to indicate a loop is still running