Momentum-Apps/protocols/toyota_tpms.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 bit 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) {
            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[8];
    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 < 64) return false; /* Require the full 8 bytes. */

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

    snprintf(info->name,sizeof(info->name),"%s","Toyota TPMS");
    snprintf(info->raw,sizeof(info->raw),"%02X%02X%02X%02X%02X%02X%02X%02X%02X",
        raw[0],raw[1],raw[2],raw[3],raw[4],raw[5],
        raw[6],raw[7],raw[8]);
    snprintf(info->info1,sizeof(info->info1),"Tire ID %02X%02X%02X%02X",
        raw[0],raw[1],raw[2],raw[3]);
    snprintf(info->info1,sizeof(info->info1),"Pressure %.2f psi", (double)kpa);
    snprintf(info->info2,sizeof(info->info2),"Temperature %d C", temp);
    return true;
}

ProtoViewDecoder ToyotaTPMSDecoder = {
    "Toyota TPMS", decode
};