thermostat/src/ad5680.rs

use crate::timer::sleep;
use stm32f4xx_hal::{
    hal::{blocking::spi::Transfer, digital::v2::OutputPin},
    spi,
    time::MegaHertz,
};

/// SPI Mode 1
pub const SPI_MODE: spi::Mode = spi::Mode {
    polarity: spi::Polarity::IdleLow,
    phase: spi::Phase::CaptureOnSecondTransition,
};
/// 30 MHz
pub const SPI_CLOCK: MegaHertz = MegaHertz(30);

pub const MAX_VALUE: u32 = 0x3FFFF;

/// [AD5680](https://www.analog.com/media/en/technical-documentation/data-sheets/AD5680.pdf) DAC
pub struct Dac<SPI: Transfer<u8>, S: OutputPin> {
    spi: SPI,
    sync: S,
}

impl<SPI: Transfer<u8>, S: OutputPin> Dac<SPI, S> {
    pub fn new(spi: SPI, mut sync: S) -> Self {
        let _ = sync.set_low();

        Dac { spi, sync }
    }

    fn write(&mut self, buf: &mut [u8]) -> Result<(), SPI::Error> {
        // pulse sync to start a new transfer. leave sync idle low
        // afterwards to save power as recommended per datasheet.
        let _ = self.sync.set_high();
        // must be high for >= 33 ns
        sleep(1);
        let _ = self.sync.set_low();
        self.spi.transfer(buf)?;
        Ok(())
    }

    pub fn set(&mut self, value: u32) -> Result<u32, SPI::Error> {
        let value = value.min(MAX_VALUE);
        let mut buf = [(value >> 14) as u8, (value >> 6) as u8, (value << 2) as u8];
        self.write(&mut buf)?;
        Ok(value)
    }
}