Struct ApllCoefficients 

pub struct ApllCoefficients {
    pub sdm0: u8,
    pub sdm1: u8,
    pub sdm2: u8,
    pub o_div: u8,
}

SDM coefficients for the ESP32 APLL.

Output frequency formula:

fout = fxtal * (sdm2 + sdm1/256 + sdm0/65536 + 4) / (2 * (o_div + 2))

For each supported on-board crystal, ApllCoefficients::for_xtal returns the coefficients that land on 50 MHz (the RMII reference clock).

Fields

sdm0: u8

Fine fractional multiplier (×1/65536). 8-bit field.

sdm1: u8

Mid fractional multiplier (×1/256). 8-bit field.

sdm2: u8

Integer-part multiplier (added to fixed +4). 6-bit field (apll_write_mask(7, 5, 0, sdm2)).

o_div: u8

Output divider field. Final divisor is 2 * (o_div + 2). 5-bit field (apll_write_mask(4, 4, 0, o_div)).

Implementations

impl ApllCoefficients

pub const fn for_xtal(xtal: XtalFreq) -> Self

Look up the coefficients that produce a 50 MHz APLL output for the given on-board crystal.

Total: infallible — the input is constrained by XtalFreq, which only enumerates crystals the crate has verified coefficients for (Mhz26 / Mhz32 / Mhz40). Adding support for another crystal therefore takes two concrete edits — extend XtalFreq with the new variant, and add a matching arm here — followed by a host-side unit test asserting the new arm lands on 50 MHz.

Verified results (target 50.000 MHz):

XTAL	sdm2	sdm1	sdm0	o_div	Computed fout
26 MHz	11	98	118	2	50.0000 MHz
32 MHz	8	128	0	2	50.0000 MHz
40 MHz	6	0	0	2	50.0000 MHz

Trait Implementations

impl Clone for ApllCoefficients

fn clone(&self) -> ApllCoefficients

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ApllCoefficients

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for ApllCoefficients

fn eq(&self, other: &ApllCoefficients) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for ApllCoefficients

impl Eq for ApllCoefficients

impl StructuralPartialEq for ApllCoefficients