portapack-mayhem/firmware/application/hw/encoder.cpp

/*
 * Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
 *
 * This file is part of PortaPack.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#include "encoder.hpp"

#include "utility.hpp"

static const int8_t transition_map[] = {
    0,   // 0000: noop
    0,   // 0001: start
    0,   // 0010: start
    0,   // 0011: rate
    1,   // 0100: end
    0,   // 0101: noop
    0,   // 0110: rate
    -1,  // 0111: end
    -1,  // 1000: end
    0,   // 1001: rate
    0,   // 1010: noop
    1,   // 1011: end
    0,   // 1100: rate
    0,   // 1101: start
    0,   // 1110: start
    0,   // 1111: noop
};

int_fast8_t Encoder::update(
    const uint_fast8_t phase_0,
    const uint_fast8_t phase_1) {
    state <<= 1;
    state |= phase_0;
    state <<= 1;
    state |= phase_1;

    return transition_map[state & 0xf];
}