Momentum-Apps/protocols/tpms/toyota.c

/* Toyota tires TPMS. Usually 443.92 Mhz FSK (In Europe).
 *
 * Preamble + sync + 64 bits of data. ~48us short pulse length.
 *
 * The preamble + sync is something like:
 *
 *   10101010101 (preamble) + 001111[1] (sync)
 *
 * Note: the final [1] means that sometimes it is four 1s, sometimes
 * five, depending on the short pulse length detection and the exact
 * duration of the high long pulse. After the sync, a differential
 * Manchester encoded payload follows. However the Flipper's CC1101
 * often can't decode correctly the initial alternating pattern 101010101,
 * so what we do is to seek just the sync, that is "001111" or "0011111",
 * however we now that it must be followed by one differenitally encoded
 * bit, so we can use also the first symbol of data to force a more robust
 * detection, and look for one of the following:
 *
 * [001111]00
 * [0011111]00
 * [001111]01
 * [0011111]01
 */

#include "../../app.h"

static bool decode(uint8_t *bits, uint32_t numbytes, uint32_t numbits, ProtoViewMsgInfo *info) {

    if (numbits-6 < 64*2) return false; /* Ask for 64 bit of data (each bit
                                           is two symbols in the bitmap). */

    char *sync[] = {
        "00111100",
        "001111100",
        "00111101",
        "001111101",
        NULL
    };

    int j;
    uint32_t off = 0;
    for (j = 0; sync[j]; j++) {
        off = bitmap_seek_bits(bits,numbytes,0,numbits,sync[j]);
        if (off != BITMAP_SEEK_NOT_FOUND) {
            info->start_off = off;
            off += strlen(sync[j])-2;
            break;
	}
    }
    if (off == BITMAP_SEEK_NOT_FOUND) return false;

    FURI_LOG_E(TAG, "Toyota TPMS sync[%s] found", sync[j]);

    uint8_t raw[9];
    uint32_t decoded =
        convert_from_diff_manchester(raw,sizeof(raw),bits,numbytes,off,true);
    FURI_LOG_E(TAG, "Toyota TPMS decoded bits: %lu", decoded);

    if (decoded < 8*9) return false; /* Require the full 8 bytes. */
    if (crc8(raw,8,0x80,7) != raw[8]) return false; /* Require sane CRC. */

    /* We detected a valid signal. However now info->start_off is actually
     * pointing to the sync part, not the preamble of alternating 0 and 1.
     * Protoview decoders get called with some space to the left, in order
     * for the decoder itself to fix the signal if neeeded, so that its
     * logical representation will be more accurate and better to save
     * and retransmit. */
    if (info->start_off >= 12) {
        info->start_off -= 12;
        bitmap_set_pattern(bits,numbytes,info->start_off,"010101010101");
    }

    info->pulses_count = (off+8*9*2) - info->start_off;

    float psi = (float)((raw[4]&0x7f)<<1 | raw[5]>>7) * 0.25 - 7;
    int temp = ((raw[5]&0x7f)<<1 | raw[6]>>7) - 40;

    fieldset_add_bytes(info->fieldset,"Tire ID",raw,4*2);
    fieldset_add_float(info->fieldset,"Pressure psi",psi,2);
    fieldset_add_int(info->fieldset,"Temperature C",temp,8);
    return true;
}

ProtoViewDecoder ToyotaTPMSDecoder = {
    .name = "Toyota TPMS",
    .decode = decode,
    .get_fields = NULL,
    .build_message = NULL
};