SystemK/Protocols/NEC.c

/*
 * This program source code file is part of SystemK, a library in the KTag project.
 *
 * 🛡️ <https://ktag.clubk.club> 🃞
 *
 * Copyright © 2016-2025 Joseph P. Kearney and the KTag developers.
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License as published by the Free
 * Software Foundation, either version 3 of the License, 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 Affero General Public License for more
 * details.
 *
 * There should be a copy of the GNU Affero General Public License in the LICENSE
 * file in the root of this repository.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdbool.h>
#include <stdio.h>

#include "SystemK.h"

#define NEC_BLUE_TEAM 0x01
#define NEC_RED_TEAM 0x02

#define NEC_HEADER_MARK_DURATION_IN_us 9000
#define NEC_HEADER_SPACE_DURATION_IN_us 4500
#define NEC_ZERO_MARK_DURATION_IN_us 562
#define NEC_ZERO_SPACE_DURATION_IN_us 562
#define NEC_ONE_MARK_DURATION_IN_us 562
#define NEC_ONE_SPACE_DURATION_IN_us 1688
#define NEC_TOLERANCE_IN_us 200

#define MIN_ZERO_MARK_IN_us (NEC_ZERO_MARK_DURATION_IN_us - NEC_TOLERANCE_IN_us)
#define MAX_ZERO_MARK_IN_us (NEC_ZERO_MARK_DURATION_IN_us + NEC_TOLERANCE_IN_us)
#define MIN_ZERO_SPACE_IN_us (NEC_ZERO_SPACE_DURATION_IN_us - NEC_TOLERANCE_IN_us)
#define MAX_ZERO_SPACE_IN_us (NEC_ZERO_SPACE_DURATION_IN_us + NEC_TOLERANCE_IN_us)
#define MIN_ONE_MARK_IN_us (NEC_ONE_MARK_DURATION_IN_us - NEC_TOLERANCE_IN_us)
#define MAX_ONE_MARK_IN_us (NEC_ONE_MARK_DURATION_IN_us + NEC_TOLERANCE_IN_us)
#define MIN_ONE_SPACE_IN_us (NEC_ONE_SPACE_DURATION_IN_us - NEC_TOLERANCE_IN_us)
#define MAX_ONE_SPACE_IN_us (NEC_ONE_SPACE_DURATION_IN_us + NEC_TOLERANCE_IN_us)

static const TimedBit_T NEC_HEADER_MARK = {.symbol = MARK, .duration = NEC_HEADER_MARK_DURATION_IN_us};
static const TimedBit_T NEC_HEADER_SPACE = {.symbol = MARK, .duration = NEC_HEADER_SPACE_DURATION_IN_us};
static const TimedBit_T NEC_ZERO_SPACE = {.symbol = SPACE, .duration = NEC_ZERO_SPACE_DURATION_IN_us};
static const TimedBit_T NEC_ONE_SPACE = {.symbol = SPACE, .duration = NEC_ONE_SPACE_DURATION_IN_us};
static const TimedBit_T NEC_ZERO_MARK = {.symbol = MARK, .duration = NEC_ZERO_MARK_DURATION_IN_us};
static const TimedBit_T NEC_ONE_MARK = {.symbol = MARK, .duration = NEC_ONE_MARK_DURATION_IN_us};
static const TimedBit_T NEC_END = {.symbol = SPACE, .duration = LAST_PULSE};

static TimedPulseTrain_T Command_Send_Buffer;
static DecodedPacket_T NEC_Command_Buffers[3] =
    {
        {.Command.type = DECODED_PACKET_TYPE_BUFFER_FREE},
        {.Command.type = DECODED_PACKET_TYPE_BUFFER_FREE},
        {.Command.type = DECODED_PACKET_TYPE_BUFFER_FREE}};

static inline DecodedPacket_T *Get_Command_Packet_Buffer(void)
{
    if (NEC_Command_Buffers[0].Command.type == DECODED_PACKET_TYPE_BUFFER_FREE)
    {
        return &NEC_Command_Buffers[0];
    }
    else if (NEC_Command_Buffers[1].Command.type == DECODED_PACKET_TYPE_BUFFER_FREE)
    {
        return &NEC_Command_Buffers[1];
    }
    else
    {
        // Just use it.
        return &NEC_Command_Buffers[2];
    }
}

static inline void PackPulseTrain(TimedPulseTrain_T *pulsetrain, uint32_t data)
{
    pulsetrain->bitstream[0] = NEC_HEADER_MARK;
    pulsetrain->bitstream[1] = NEC_HEADER_SPACE;

    for (uint8_t n = 0; n < 16; n++)
    {
        if ((data & 0x80000000) == 0x80000000)
        {
            pulsetrain->bitstream[1 + (n * 2)] = NEC_ONE_SPACE;
        }
        else
        {
            pulsetrain->bitstream[1 + (n * 2)] = NEC_ZERO_SPACE;
        }
        data = data << 1;
        if ((data & 0x80000000) == 0x80000000)
        {
            pulsetrain->bitstream[2 + (n * 2)] = NEC_ONE_MARK;
        }
        else
        {
            pulsetrain->bitstream[2 + (n * 2)] = NEC_ZERO_MARK;
        }
        data = data << 1;
    }

    pulsetrain->bitstream[(2 * 20) + 1] = NEC_END;
}

TimedPulseTrain_T *NEC_EncodePacket(CommandPacket_T *packet)
{
    uint32_t packed_data = 0x00000000;

    PackPulseTrain(&Command_Send_Buffer, packed_data);

    return &Command_Send_Buffer;
}

DecodedPacket_T *NEC_MaybeDecodePacket(TimedPulseTrain_T *packet)
{
    // Sometimes the Roku remote will repeat keys, so only check for a minimum here.
    if (packet->count < 67)
    {
        // Fail fast!
        return NULL;
    }
    else
    {
        // Convert pulse durations to bits.
        // packet->bitstream[0] is the header mark--ignore it.
        // packet->bitstream[1] is the header space--ignore it, too.

        uint32_t data = 0;
        for (uint8_t n = 0; n < 32; n++)
        {
            uint8_t mark_index = (n * 2) + 2;
            uint8_t space_index = (n * 2) + 3;

            if ((packet->bitstream[mark_index].duration > MIN_ONE_MARK_IN_us) && (packet->bitstream[mark_index].duration < MAX_ONE_MARK_IN_us) &&
                (packet->bitstream[space_index].duration > MIN_ONE_SPACE_IN_us) && (packet->bitstream[space_index].duration < MAX_ONE_SPACE_IN_us))
            {
                // One
                data |= ((uint32_t)1 << n);
            }
            else if ((packet->bitstream[mark_index].duration > MIN_ZERO_MARK_IN_us) && (packet->bitstream[mark_index].duration < MAX_ZERO_MARK_IN_us) &&
                     (packet->bitstream[space_index].duration > MIN_ZERO_SPACE_IN_us) && (packet->bitstream[space_index].duration < MAX_ZERO_SPACE_IN_us))
            {
                // Zero--nothing to do.
            }
            else
            {
                // This mark is neither a zero or a one; abort.
                return NULL;
            }
        }

        // PulseDurations[66] is the end-of-message mark.  It can also be ignored.
        DecodedPacket_T *Command_Rx_Buffer = Get_Command_Packet_Buffer();
        Command_Rx_Buffer->Command.type = DECODED_PACKET_TYPE_COMMAND_RECEIVED;
        Command_Rx_Buffer->Command.protocol = NEC_PROTOCOL;
        Command_Rx_Buffer->Command.data = data;
        return Command_Rx_Buffer;
    }
}

color_t NEC_GetTeamColor(uint8_t team_ID)
{
    (void)team_ID;

    return COLOR_BLACK;
}