unleashed-firmware/applications/plugins/protoview/protocols/tpms/renault.c

/* Renault tires TPMS. Usually 443.92 Mhz FSK.
 *
 * Preamble + sync + Manchester bits. ~48us short pulse.
 * 9 Bytes in total not counting the preamble. */

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

#define USE_TEST_VECTOR 0
static const char* test_vector =
    "...01010101010101010110" // Preamble + sync

    /* The following is Marshal encoded, so each two characters are
     * actaully one bit. 01 = 0, 10 = 1. */
    "010110010110" // Flags.
    "10011001101010011001" // Pressure, multiply by 0.75 to obtain kpa.
    // 244 kpa here.
    "1010010110011010" // Temperature, subtract 30 to obtain celsius. 22C here.
    "1001010101101001"
    "0101100110010101"
    "1001010101100110" // Tire ID. 0x7AD779 here.
    "0101010101010101"
    "0101010101010101" // Two FF bytes (usually). Unknown.
    "0110010101010101"; // CRC8 with (poly 7, initialization 0).

static bool decode(uint8_t* bits, uint32_t numbytes, uint32_t numbits, ProtoViewMsgInfo* info) {
    if(USE_TEST_VECTOR) { /* Test vector to check that decoding works. */
        bitmap_set_pattern(bits, numbytes, 0, test_vector);
        numbits = strlen(test_vector);
    }

    if(numbits - 12 < 9 * 8) return false;

    const char* sync_pattern = "01010101010101010110";
    uint64_t off = bitmap_seek_bits(bits, numbytes, 0, numbits, sync_pattern);
    if(off == BITMAP_SEEK_NOT_FOUND) return false;
    FURI_LOG_E(TAG, "Renault TPMS preamble+sync found");

    info->start_off = off;
    off += 20; /* Skip preamble. */

    uint8_t raw[9];
    uint32_t decoded = convert_from_line_code(
        raw, sizeof(raw), bits, numbytes, off, "01", "10"); /* Manchester. */
    FURI_LOG_E(TAG, "Renault TPMS decoded bits: %lu", decoded);

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

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

    float kpa = 0.75 * ((uint32_t)((raw[0] & 3) << 8) | raw[1]);
    int temp = raw[2] - 30;

    snprintf(info->name, sizeof(info->name), "%s", "Renault 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", raw[3], raw[4], raw[5]);
    snprintf(info->info2, sizeof(info->info2), "Pressure %.2f kpa", (double)kpa);
    snprintf(info->info3, sizeof(info->info3), "Temperature %d C", temp);
    return true;
}

ProtoViewDecoder RenaultTPMSDecoder = {"Renault TPMS", decode};