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Fixing calculation bug pointed out by @tdittr

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This commit is contained in:
Nic0w 2021-04-25 00:36:46 +02:00
parent 568cafe2d1
commit d5cbd44ade
1 changed files with 8 additions and 6 deletions
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14
rp2040-hal/src/xosc.rs
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@ -92,7 +92,7 @@ impl CrystalOscillator<Disabled> {
const ALLOWED_FREQUENCY_RANGE: RangeInclusive<Megahertz<u32>> = Megahertz(1)..=Megahertz(15);
const STABLE_DELAY: Milliseconds = Milliseconds(1_u32);
const DIVIDER: Fraction = Fraction::new(1, 256);
const DIVIDER: Fraction = Fraction::new(256, 1);
if !ALLOWED_FREQUENCY_RANGE.contains(&frequency) {
return Err(Error::FrequencyOutOfRange)
@ -103,12 +103,14 @@ impl CrystalOscillator<Disabled> {
w
});
let delay_sec: Seconds = STABLE_DELAY.into();
//1 ms = 10e-3 sec and Freq = 1/T where T is in seconds so 1ms converts to 1000Hz
let delay_to_hz: Hertz = STABLE_DELAY.to_rate();
//startup_delay = ((freq_hz * 10e-3) / 256; See Chapter 2, Section 16, §3)
//startup_delay = ((freq_hz * 10e-3) / 256) = ((freq_hz / 1000) / 256)
//See Chapter 2, Section 16, §3)
//We do the calculation first.
let startup_delay = delay_sec.
checked_mul(frequency.integer()).and_then(|r|
let startup_delay = frequency.
checked_div(delay_to_hz.integer()).and_then(|r|
r.to_generic::<u32>(DIVIDER).ok()
).
ok_or(Error::BadArgument)?;
@ -118,7 +120,7 @@ impl CrystalOscillator<Disabled> {
map_err(|_|Error::BadArgument)?;
self.device.startup.write(|w| unsafe {
w.delay().bits(startup_delay);
w.delay().bits(startup_delay+1);
w
});