cmdr-joystick/rp2040/src/elrs.rs

//! Project: CMtec CMDR joystick 24
//! Date:    2023-08-01
//! Author:  Christoffer Martinsson
//! Email:   cm@cmtec.se
//! License: Please refer to LICENSE in root directory

use embedded_hal::serial::Read;
use rp2040_hal::uart::{Enabled, State, UartDevice, UartPeripheral, ValidUartPinout};

const CRSF_CRC8TAB: [u8; 256] = [
    0x00, 0xD5, 0x7F, 0xAA, 0xFE, 0x2B, 0x81, 0x54, 0x29, 0xFC, 0x56, 0x83, 0xD7, 0x02, 0xA8, 0x7D,
    0x52, 0x87, 0x2D, 0xF8, 0xAC, 0x79, 0xD3, 0x06, 0x7B, 0xAE, 0x04, 0xD1, 0x85, 0x50, 0xFA, 0x2F,
    0xA4, 0x71, 0xDB, 0x0E, 0x5A, 0x8F, 0x25, 0xF0, 0x8D, 0x58, 0xF2, 0x27, 0x73, 0xA6, 0x0C, 0xD9,
    0xF6, 0x23, 0x89, 0x5C, 0x08, 0xDD, 0x77, 0xA2, 0xDF, 0x0A, 0xA0, 0x75, 0x21, 0xF4, 0x5E, 0x8B,
    0x9D, 0x48, 0xE2, 0x37, 0x63, 0xB6, 0x1C, 0xC9, 0xB4, 0x61, 0xCB, 0x1E, 0x4A, 0x9F, 0x35, 0xE0,
    0xCF, 0x1A, 0xB0, 0x65, 0x31, 0xE4, 0x4E, 0x9B, 0xE6, 0x33, 0x99, 0x4C, 0x18, 0xCD, 0x67, 0xB2,
    0x39, 0xEC, 0x46, 0x93, 0xC7, 0x12, 0xB8, 0x6D, 0x10, 0xC5, 0x6F, 0xBA, 0xEE, 0x3B, 0x91, 0x44,
    0x6B, 0xBE, 0x14, 0xC1, 0x95, 0x40, 0xEA, 0x3F, 0x42, 0x97, 0x3D, 0xE8, 0xBC, 0x69, 0xC3, 0x16,
    0xEF, 0x3A, 0x90, 0x45, 0x11, 0xC4, 0x6E, 0xBB, 0xC6, 0x13, 0xB9, 0x6C, 0x38, 0xED, 0x47, 0x92,
    0xBD, 0x68, 0xC2, 0x17, 0x43, 0x96, 0x3C, 0xE9, 0x94, 0x41, 0xEB, 0x3E, 0x6A, 0xBF, 0x15, 0xC0,
    0x4B, 0x9E, 0x34, 0xE1, 0xB5, 0x60, 0xCA, 0x1F, 0x62, 0xB7, 0x1D, 0xC8, 0x9C, 0x49, 0xE3, 0x36,
    0x19, 0xCC, 0x66, 0xB3, 0xE7, 0x32, 0x98, 0x4D, 0x30, 0xE5, 0x4F, 0x9A, 0xCE, 0x1B, 0xB1, 0x64,
    0x72, 0xA7, 0x0D, 0xD8, 0x8C, 0x59, 0xF3, 0x26, 0x5B, 0x8E, 0x24, 0xF1, 0xA5, 0x70, 0xDA, 0x0F,
    0x20, 0xF5, 0x5F, 0x8A, 0xDE, 0x0B, 0xA1, 0x74, 0x09, 0xDC, 0x76, 0xA3, 0xF7, 0x22, 0x88, 0x5D,
    0xD6, 0x03, 0xA9, 0x7C, 0x28, 0xFD, 0x57, 0x82, 0xFF, 0x2A, 0x80, 0x55, 0x01, 0xD4, 0x7E, 0xAB,
    0x84, 0x51, 0xFB, 0x2E, 0x7A, 0xAF, 0x05, 0xD0, 0xAD, 0x78, 0xD2, 0x07, 0x53, 0x86, 0x2C, 0xF9,
];

const CONNECTION_TIMEOUT: u16 = 500;
const INIT_TIMEOUT: u16 = 1000;

pub struct Elrs<S: State, D: UartDevice, P>
where
    S: State,
    D: UartDevice,
    P: ValidUartPinout<D>,
{
    uart: UartPeripheral<S, D, P>,
    elsr_init_done: bool,
    elrs_init_counter: u16,
    elrs_connected: bool,
    elrs_connected_timeout: u16,
    rx_buffer_index: usize,
}

impl<S, D, P> Elrs<S, D, P>
where
    S: State,
    D: UartDevice,
    P: ValidUartPinout<D>,
{
    pub fn new(uart: UartPeripheral<S, D, P>) -> Self {
        let elsr_init_done = false;
        let elrs_init_counter = 0;
        let elrs_connected = false;
        let elrs_connected_timeout = CONNECTION_TIMEOUT;
        let rx_buffer_index = 0;
        Self {
            uart,
            elsr_init_done,
            elrs_init_counter,
            elrs_connected,
            elrs_connected_timeout,
            rx_buffer_index,
        }
    }
}

impl<D, P> Elrs<Enabled, D, P>
where
    D: UartDevice,
    P: ValidUartPinout<D>,
{
    pub fn send(&mut self, data: [u16; 12]) {
        if self.elsr_init_done {
            self.uart
                .write_full_blocking(&self.prepare_crsf_data_packet(data));
            return;
        }
        if self.elrs_init_counter < INIT_TIMEOUT {
            self.uart
                .write_full_blocking(&self.prepare_crsf_data_packet(data));
            self.elrs_init_counter += 1;
        } else if self.elrs_init_counter < INIT_TIMEOUT + 5 {
            self.uart
                // Setting Packet Rate to 150Hz
                // 0 = 50Hz LoRa, 1 = 100Hz Full, 2 = 150Hz LoRa, 3 = 250Hz LoRa,
                // 4 = 333H Full, 5 = 500Hz LoRa, 6 = 250Hz DejaVu, 7 = 500Hz DejaVu,
                // 8 = 500Hz FLRC, 9 = 1000Hz FLRC
                .write_full_blocking(&self.prepare_crsf_cmd_packet(0x01, 0x00));
            self.elrs_init_counter += 1;
        } else if self.elrs_init_counter < INIT_TIMEOUT + 10 {
            self.uart
                // Setting Power to 10mW
                // 0 = 10mW, 1 = 25mW, 2 = 50mW, 3 = 100mW,
                // 4 = 200mW, 5 = 500mW, 6 = 1000mW, 7 = 2000mW
                .write_full_blocking(&self.prepare_crsf_cmd_packet(0x06, 0x00));
            self.elrs_init_counter += 1;
        } else {
            self.elsr_init_done = true;
        }

        self.check_link_frame();
    }

    pub fn connected(&self) -> bool {
        self.elrs_connected
    }

    pub fn reset(&mut self) {
        self.elsr_init_done = false;
        self.elrs_init_counter = 0;
    }

    fn check_link_frame(&mut self) {
        if self.elrs_connected_timeout == 0 {
            self.elrs_connected = false;
        } else {
            self.elrs_connected_timeout -= 1;
        }

        let mut rx_byte: u8;

        while self.uart.uart_is_readable() {
            match self.uart.read() {
                Ok(byte) => {
                    rx_byte = byte;
                }
                Err(_) => {
                    continue;
                }
            }

            // Simple RX telemetry link frame detection: 0xEA, 0xXX, 0x14
            if (rx_byte == 0xEA && self.rx_buffer_index == 0) || self.rx_buffer_index == 1 {
                self.rx_buffer_index += 1;
            } else if rx_byte == 0x14 && self.rx_buffer_index == 2 {
                self.elrs_connected = true;
                self.elrs_connected_timeout = CONNECTION_TIMEOUT;
                self.rx_buffer_index = 0;
            } else {
                self.rx_buffer_index = 0;
            }
        }
    }

    fn prepare_crsf_data_packet(&self, data: [u16; 12]) -> [u8; 26] {
        let mut packet: [u8; 26] = [0; 26];
        let mut crc: u8 = 0;
        packet[0] = 0xEE;
        packet[1] = 0x18;
        packet[2] = 0x16;
        packet[3] = data[0] as u8;
        packet[4] = ((data[0] >> 8) | (data[1] << 3)) as u8;
        packet[5] = ((data[1] >> 5) | (data[2] << 6)) as u8;
        packet[6] = (data[2] >> 2) as u8;
        packet[7] = ((data[2] >> 10) | (data[3] << 1)) as u8;
        packet[8] = ((data[3] >> 7) | (data[4] << 4)) as u8;
        packet[9] = ((data[4] >> 4) | (data[5] << 7)) as u8;
        packet[10] = (data[5] >> 1) as u8;
        packet[11] = ((data[5] >> 9) | (data[6] << 2)) as u8;
        packet[12] = ((data[6] >> 6) | (data[7] << 5)) as u8;
        packet[13] = (data[7] >> 3) as u8;
        packet[14] = data[8] as u8;
        packet[15] = ((data[8] >> 8) | (data[9] << 3)) as u8;
        packet[16] = ((data[9] >> 5) | (data[10] << 6)) as u8;
        packet[17] = (data[10] >> 2) as u8;
        packet[18] = ((data[10] >> 10) | (data[11] << 1)) as u8;
        packet[19] = (data[11] >> 7) as u8;
        // Channel 13-16 are not used in ELRS
        for i in 2..25 {
            crc = CRSF_CRC8TAB[(crc ^ packet[i]) as usize];
        }
        packet[25] = crc;
        packet
    }

    fn prepare_crsf_cmd_packet(&self, command: u8, value: u8) -> [u8; 8] {
        let mut packet: [u8; 8] = [0; 8];
        let mut crc: u8 = 0;
        packet[0] = 0xEE;
        packet[1] = 0x06;
        packet[2] = 0x2D;
        packet[3] = 0xEE;
        packet[4] = 0xEA;
        packet[5] = command;
        packet[6] = value;
        for i in 2..7 {
            crc = CRSF_CRC8TAB[(crc ^ packet[i]) as usize];
        }
        packet[7] = crc;
        packet
    }
}