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//! Serial Peripheral Interface
use nb;
/// Full duplex (master mode)
///
/// # Notes
///
/// - It's the task of the user of this interface to manage the slave select lines
///
/// - Due to how full duplex SPI works each `read` call must be preceded by a `send` call.
///
/// - Some SPIs can work with 8-bit *and* 16-bit words. You can overload this trait with different
/// `Word` types to allow operation in both modes.
pub trait FullDuplex<Word> {
/// An enumeration of SPI errors
type Error;
/// Reads the word stored in the shift register
///
/// **NOTE** A word must be sent to the slave before attempting to call this
/// method.
fn read(&mut self) -> nb::Result<Word, Self::Error>;
/// Sends a word to the slave
fn send(&mut self, word: Word) -> nb::Result<(), Self::Error>;
}
/// Clock polarity
#[derive(Clone, Copy, PartialEq, Eq)]
pub enum Polarity {
/// Clock signal low when idle
IdleLow,
/// Clock signal high when idle
IdleHigh,
}
/// Clock phase
#[derive(Clone, Copy, PartialEq, Eq)]
pub enum Phase {
/// Data in "captured" on the first clock transition
CaptureOnFirstTransition,
/// Data in "captured" on the second clock transition
CaptureOnSecondTransition,
}
/// SPI mode
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct Mode {
/// Clock polarity
pub polarity: Polarity,
/// Clock phase
pub phase: Phase,
}
/// Helper for CPOL = 0, CPHA = 0
pub const MODE_0: Mode = Mode {
polarity: Polarity::IdleLow,
phase: Phase::CaptureOnFirstTransition,
};
/// Helper for CPOL = 0, CPHA = 1
pub const MODE_1: Mode = Mode {
polarity: Polarity::IdleLow,
phase: Phase::CaptureOnSecondTransition,
};
/// Helper for CPOL = 1, CPHA = 0
pub const MODE_2: Mode = Mode {
polarity: Polarity::IdleHigh,
phase: Phase::CaptureOnFirstTransition,
};
/// Helper for CPOL = 1, CPHA = 1
pub const MODE_3: Mode = Mode {
polarity: Polarity::IdleHigh,
phase: Phase::CaptureOnSecondTransition,
};