nrf-hal-common 0.18.0

Implementation details of the nRF HAL crates. Don't use this directly, use one of the specific HAL crates instead (`nrfXYZ-hal`).
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//! Delays.

use crate::clocks::HFCLK_FREQ;
use core::convert::TryInto;
use cortex_m::peripheral::syst::SystClkSource;
use cortex_m::peripheral::SYST;
use embedded_hal::delay::DelayNs;

/// System timer (SysTick) as a delay provider.
pub struct Delay {
    syst: SYST,
}

impl Delay {
    /// Configures the system timer (SysTick) as a delay provider.
    pub fn new(mut syst: SYST) -> Self {
        syst.set_clock_source(SystClkSource::Core);

        Delay { syst }
    }

    /// Releases the system timer (SysTick) resource.
    pub fn free(self) -> SYST {
        self.syst
    }
}

#[cfg(feature = "embedded-hal-02")]
impl embedded_hal_02::blocking::delay::DelayMs<u32> for Delay {
    fn delay_ms(&mut self, ms: u32) {
        DelayNs::delay_ms(self, ms);
    }
}

#[cfg(feature = "embedded-hal-02")]
impl embedded_hal_02::blocking::delay::DelayMs<u16> for Delay {
    fn delay_ms(&mut self, ms: u16) {
        DelayNs::delay_ms(self, ms.into());
    }
}

#[cfg(feature = "embedded-hal-02")]
impl embedded_hal_02::blocking::delay::DelayMs<u8> for Delay {
    fn delay_ms(&mut self, ms: u8) {
        DelayNs::delay_ms(self, ms.into());
    }
}

#[cfg(feature = "embedded-hal-02")]
impl embedded_hal_02::blocking::delay::DelayUs<u32> for Delay {
    fn delay_us(&mut self, us: u32) {
        DelayNs::delay_us(self, us);
    }
}

#[cfg(feature = "embedded-hal-02")]
impl embedded_hal_02::blocking::delay::DelayUs<u16> for Delay {
    fn delay_us(&mut self, us: u16) {
        DelayNs::delay_us(self, us.into());
    }
}

#[cfg(feature = "embedded-hal-02")]
impl embedded_hal_02::blocking::delay::DelayUs<u8> for Delay {
    fn delay_us(&mut self, us: u8) {
        DelayNs::delay_us(self, us.into());
    }
}

impl DelayNs for Delay {
    fn delay_ns(&mut self, ns: u32) {
        // The SysTick Reload Value register supports values between 1 and 0x00FFFFFF.
        const MAX_RVR: u32 = 0x00FF_FFFF;

        let mut total_rvr: u32 = (u64::from(ns) * u64::from(HFCLK_FREQ) / 1_000_000_000)
            .try_into()
            .unwrap();

        while total_rvr != 0 {
            let current_rvr = if total_rvr <= MAX_RVR {
                total_rvr
            } else {
                MAX_RVR
            };

            self.syst.set_reload(current_rvr);
            self.syst.clear_current();
            self.syst.enable_counter();

            // Update the tracking variable while we are waiting...
            total_rvr -= current_rvr;

            while !self.syst.has_wrapped() {}

            self.syst.disable_counter();
        }
    }
}