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// ------------------------------------------------------------------------------
// Copyright 2018 Uwe Arzt, mail@uwe-arzt.de
// SPDX-License-Identifier: Apache-2.0
// ------------------------------------------------------------------------------

//! Driver for AMS AS5048A Magnetic Rotary Encoder

#![no_std]

extern crate embedded_hal as hal;

use hal::blocking::spi::Transfer;
use hal::digital::OutputPin;
use hal::spi::{Mode, Phase, Polarity};

#[allow(dead_code)]
#[derive(Copy, Clone)]
enum Register {
    ClearErrorFlag = 0x0001,
    ProgrammingControl = 0x0003,
    OtpRegisterZeroPosHigh = 0x0016,
    OtpRegisterZeroPosLow = 0x0017,
    DiagAgc = 0x3FFD,
    Magnitude = 0x3FFE,
    Angle = 0x3FFF,
}

pub struct AS5048A<SPI, CS> {
    spi: SPI,
    cs: CS,
}

impl<SPI, CS, E> AS5048A<SPI, CS>
where
    SPI: Transfer<u8, Error = E>,
    CS: OutputPin,
{
    pub fn new(spi: SPI, cs: CS) -> Result<Self, E> {
        let as5048 = AS5048A { spi: spi, cs: cs };

        Ok(as5048)
    }

    pub fn diag_gain(&mut self) -> Result<(u8, u8), E> {
        match self.read(Register::DiagAgc) {
            Ok(arr) => Ok((arr[0] & 0x0f, arr[1])),
            Err(e) => Err(e),
        }
    }
    pub fn magnitude(&mut self) -> Result<u16, E> {
        self.read_u16(Register::Magnitude)
    }
    pub fn angle(&mut self) -> Result<u16, E> {
        self.read_u16(Register::Angle)
    }

    fn read_u16(&mut self, reg: Register) -> Result<u16, E> {
        match self.read(reg) {
            Ok(arr) => {
                let y = u16::from_be_bytes(arr);
                Ok(y & 0b0011_1111_1111_1111)
            }
            Err(e) => Err(e),
        }
    }
    fn read(&mut self, reg: Register) -> Result<[u8; 2], E> {
        // send cmd
        let mut cmd: u16 = 0b_0100_0000_0000_0000;
        cmd = cmd | reg as u16;
        cmd = set_parity(cmd);

        let mut bytes = cmd.to_be_bytes();

        self.cs.set_low();
        self.spi.transfer(&mut bytes)?;
        self.cs.set_high();

        // send nop to get result back
        let mut nop = [0x00, 0x00];
        self.cs.set_low();
        self.spi.transfer(&mut nop)?;
        self.cs.set_high();

        return Ok(nop);
    }
}

fn set_parity(par: u16) -> u16 {
    let mut x = par;

    x = (x & 0x00FF) ^ (x >> 8);
    x = (x & 0x000F) ^ (x >> 4);
    x = (x & 0x0003) ^ (x >> 2);
    x = (x & 0x0001) ^ (x >> 1);

    if x == 0x0001 {
        par | 0b1000_0000_0000_0000
    } else {
        par
    }
}