rtl_433/src/devices/ge_coloreffects.c

/** @file
    GE Color Effects Remote.

    Copyright (C) 2017 Luke Cyca <me@lukecyca.com>, Christian W. Zuckschwerdt <zany@triq.net>

    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 of the License, or
    (at your option) any later version.
*/
/** @fn int ge_coloreffects_decode(r_device *decoder, bitbuffer_t *bitbuffer, unsigned row, unsigned start_pos)
GE Color Effects Remote.

Previous work decoding this device:
- https://lukecyca.com/2013/g35-rf-remote.html
- http://www.deepdarc.com/2010/11/27/hacking-christmas-lights/
*/

#include "decoder.h"

// Helper to access single bit (copied from bitbuffer.c)
static inline int bit(const uint8_t *bytes, unsigned bit)
{
    return bytes[bit >> 3] >> (7 - (bit & 7)) & 1;
}

/**
Decodes the following encoding scheme:
- 10 = 0
- 1100 = 1
*/
static unsigned ge_decode(bitbuffer_t *inbuf, unsigned row, unsigned start, bitbuffer_t *outbuf)
{
    uint8_t *bits = inbuf->bb[row];
    unsigned int len = inbuf->bits_per_row[row];
    unsigned int ipos = start;

    while (ipos < len) {
        uint8_t bit1 = bit(bits, ipos++);
        uint8_t bit2 = bit(bits, ipos++);

        if (bit1 == 1 && bit2 == 0) {
            bitbuffer_add_bit(outbuf, 0);
        } else if (bit1 == 1 && bit2 == 1) {
            // Get two more bits
            bit1 = bit(bits, ipos++);
            bit2 = bit(bits, ipos++);
            if (bit1 == 0 && bit2 == 0) {
                bitbuffer_add_bit(outbuf, 1);
            } else {
                break;
            }
        } else {
            break;
        }
    }

    return ipos;
}

static int ge_coloreffects_decode(r_device *decoder, bitbuffer_t *bitbuffer, unsigned row, unsigned start_pos)
{
    data_t *data;
    bitbuffer_t packet_bits = {0};

    ge_decode(bitbuffer, row, start_pos, &packet_bits);
    //decoder_log_bitbuffer(decoder, 0, __func__, &packet_bits, "");

    /* From http://www.deepdarc.com/2010/11/27/hacking-christmas-lights/
     * Decoded frame format is:
     *   Preamble
     *   Two zero bits
     *   6-bit Device ID (Can be modified by adding R15-R20 on the large PCB)
     *   8-bit Command
     *   One zero bit
     */

    // Frame should be 17 decoded bits (not including preamble)
    if (packet_bits.bits_per_row[0] != 17)
        return DECODE_ABORT_LENGTH;

    uint8_t *b = packet_bits.bb[0];

    // First two bits must be 0
    if (b[0] & 0xc0)
        return DECODE_FAIL_SANITY;

    // Last bit must be 0
    if (b[2] & 0x80)
        return DECODE_FAIL_SANITY;

    // Extract device ID
    // We want bits [2..8]. Since the first two bits are zero, we'll just take the entire first byte
    int device_id = b[0];

    // Extract command from the second byte
    uint8_t command = b[1];

    char cmd[7];
    switch (command) {
    case 0x5a: snprintf(cmd, sizeof(cmd), "change"); break;
    case 0xaa: snprintf(cmd, sizeof(cmd), "on"); break;
    case 0x55: snprintf(cmd, sizeof(cmd), "off"); break;
    default:
        snprintf(cmd, sizeof(cmd), "0x%x", command);
        break;
    }

    // Format data
    /* clang-format off */
    data = data_make(
            "model",        "",     DATA_STRING, "GE-ColorEffects",
            "id",           "",     DATA_FORMAT, "0x%x", DATA_INT, device_id,
            "command",      "",     DATA_STRING, cmd,
            NULL);
    /* clang-format on */

    decoder_output_data(decoder, data);
    return 1;
}

/**
GE Color Effects Remote.
@sa ge_coloreffects_decode()
*/
static int ge_coloreffects_callback(r_device *decoder, bitbuffer_t *bitbuffer)
{
    // Frame preamble:
    // 11001100 11001100 11001100 11001100 11001100 11111111 00000000
    // c   c    c   c    c   c    c   c    c   c    f   f    0   0
    uint8_t const preamble_pattern[3] = {0xcc, 0xff, 0x00};
    // Sync pulse/gap might be sliced short
    uint8_t const preamble_pattern2[3] = {0xcc, 0xfe, 0x00};

    unsigned bitpos = 0;
    unsigned found  = 0;
    int ret         = 0;
    int events      = 0;

    // Find a preamble with enough bits after it that it could be a complete packet
    // (if the device id and command were all zeros)
    while ((found = bitbuffer_search(bitbuffer, 0, bitpos, preamble_pattern, 24) + 24) + 33 <=
                    bitbuffer->bits_per_row[0]
            || (found = bitbuffer_search(bitbuffer, 0, bitpos, preamble_pattern, 23) + 23) + 33 <=
                    bitbuffer->bits_per_row[0]
            || (found = bitbuffer_search(bitbuffer, 0, bitpos, preamble_pattern2, 23) + 23) + 33 <=
                    bitbuffer->bits_per_row[0]
            || (found = bitbuffer_search(bitbuffer, 0, bitpos, preamble_pattern2, 22) + 22) + 33 <=
                    bitbuffer->bits_per_row[0]) {
        bitpos = found;
        ret = ge_coloreffects_decode(decoder, bitbuffer, 0, bitpos);
        if (ret > 0)
            events += ret;
        bitpos++;
    }

    return events > 0 ? events : ret;
}

static char const *const output_fields[] = {
        "model",
        "id",
        "command",
        NULL,
};

r_device const ge_coloreffects = {
        .name        = "GE Color Effects",
        .modulation  = FSK_PULSE_PCM,
        .short_width = 52,
        .long_width  = 52,
        .reset_limit = 450, // Maximum gap size before End Of Message [us].
        .decode_fn   = &ge_coloreffects_callback,
        .fields      = output_fields,
};