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U5: Apply auto-calibration on MSIK and calculate frequencies for detuned LSE input

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This commit is contained in:
Frank Stevenson 2025-06-17 14:27:37 +02:00
parent 6186d111a5
commit 7fe4547ecb
1 changed files with 31 additions and 3 deletions
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34
embassy-stm32/src/rcc/u5.rs
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@ -5,7 +5,7 @@ pub use crate::pac::rcc::vals::{
Hpre as AHBPrescaler, Msirange, Msirange as MSIRange, Plldiv as PllDiv, Pllm as PllPreDiv, Plln as PllMul,
Pllsrc as PllSource, Ppre as APBPrescaler, Sw as Sysclk,
};
use crate::pac::rcc::vals::{Hseext, Msirgsel, Pllmboost, Pllrge};
use crate::pac::rcc::vals::{Hseext, Msipllsel, Msirgsel, Pllmboost, Pllrge};
#[cfg(all(peri_usb_otg_hs))]
pub use crate::pac::{syscfg::vals::Usbrefcksel, SYSCFG};
use crate::pac::{FLASH, PWR, RCC};
@ -131,7 +131,18 @@ pub(crate) unsafe fn init(config: Config) {
PWR.vosr().modify(|w| w.set_vos(config.voltage_range));
while !PWR.vosr().read().vosrdy() {}
let msis = config.msis.map(|range| {
let lse_calibration_freq = match config.ls.lse {
Some(lse_config) => {
if lse_config.peripherals_clocked && (31_000..=34_000).contains(&lse_config.frequency.0) {
Some(lse_config.frequency)
} else {
None
}
}
_ => None,
};
let mut msis = config.msis.map(|range| {
// Check MSI output per RM0456 § 11.4.10
match config.voltage_range {
VoltageScale::RANGE4 => {
@ -184,8 +195,25 @@ pub(crate) unsafe fn init(config: Config) {
RCC.cr().modify(|w| {
w.set_msikon(true);
});
if lse_calibration_freq.is_some() {
// Enable the MSIK auto-calibration feature
RCC.cr().modify(|w| w.set_msipllsel(Msipllsel::MSIK));
RCC.cr().modify(|w| w.set_msipllen(true));
}
while !RCC.cr().read().msikrdy() {}
msirange_to_hertz(range)
if let Some(freq) = lse_calibration_freq {
// Estimate frequency based on it being a fixed fractional multiple of LSE
let base = msirange_to_hertz(range).0;
let multiplier = (base + 8096) / 16384;
let msik_freq = Hertz(freq.0 * multiplier / 2);
if config.msis == config.msik {
// If MSIS and MSIK are the same range both will be auto calibrated to the same frequency
msis = Some(msik_freq)
}
msik_freq
} else {
msirange_to_hertz(range)
}
});
let hsi = config.hsi.then(|| {