unleashed-firmware/applications/plugins/protoview/protocols/tpms/schrader.c
2023-01-18 22:25:39 +03:00

81 lines
2.7 KiB
C

/* Schrader TPMS. Usually 443.92 Mhz OOK, 120us pulse len.
*
* 500us high pulse + Preamble + Manchester coded bits where:
* 1 = 10
* 0 = 01
*
* 60 bits of data total (first 4 nibbles is the preamble, 0xF).
*
* Used in FIAT-Chrysler, Mercedes, ... */
#include "../../app.h"
#define USE_TEST_VECTOR 0
static const char* test_vector =
"000000111101010101011010010110010110101001010110100110011001100101010101011010100110100110011010101010101010101010101010101010101010101010101010";
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 < 64) return false; /* Preamble + data. */
const char* sync_pattern = "1111010101"
"01011010";
uint64_t off = bitmap_seek_bits(bits, numbytes, 0, numbits, sync_pattern);
if(off == BITMAP_SEEK_NOT_FOUND) return false;
FURI_LOG_E(TAG, "Schrader TPMS gap+preamble found");
info->start_off = off;
off += 10; /* Skip just the long pulse and the first 3 bits of sync, so
that we have the first byte of data with the sync nibble
0011 = 0x3. */
uint8_t raw[8];
uint32_t decoded = convert_from_line_code(
raw, sizeof(raw), bits, numbytes, off, "01", "10"); /* Manchester code. */
FURI_LOG_E(TAG, "Schrader TPMS decoded bits: %lu", decoded);
if(decoded < 64) return false; /* Require the full 8 bytes. */
raw[0] |= 0xf0; // Fix the preamble nibble for checksum computation.
uint8_t cksum = crc8(raw, sizeof(raw) - 1, 0xf0, 0x7);
if(cksum != raw[7]) {
FURI_LOG_E(TAG, "Schrader TPMS checksum mismatch");
return false;
}
info->pulses_count = (off + 8 * 8 * 2) - info->start_off;
float kpa = (float)raw[5] * 2.5;
int temp = raw[6] - 50;
snprintf(info->name, sizeof(info->name), "%s", "Schrader TPMS");
snprintf(
info->raw,
sizeof(info->raw),
"%02X%02X%02X%02X%02X%02X%02X%02X",
raw[0],
raw[1],
raw[2],
raw[3],
raw[4],
raw[5],
raw[6],
raw[7]);
snprintf(
info->info1,
sizeof(info->info1),
"Tire ID %01X%02X%02X%02X",
raw[1] & 7,
raw[2],
raw[3],
raw[4]); /* Only 28 bits of ID, not 32. */
snprintf(info->info2, sizeof(info->info2), "Pressure %.2f kpa", (double)kpa);
snprintf(info->info3, sizeof(info->info3), "Temperature %d C", temp);
return true;
}
ProtoViewDecoder SchraderTPMSDecoder = {"Schrader TPMS", decode};