mirror of
https://github.com/DarkFlippers/unleashed-firmware
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70 lines
2.5 KiB
C
70 lines
2.5 KiB
C
/* Copyright (C) 2022-2023 Salvatore Sanfilippo -- All Rights Reserved
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* See the LICENSE file for information about the license.
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*
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* Schrader TPMS. Usually 443.92 Mhz OOK, 120us pulse len.
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*
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* 500us high pulse + Preamble + Manchester coded bits where:
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* 1 = 10
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* 0 = 01
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*
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* 60 bits of data total (first 4 nibbles is the preamble, 0xF).
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*
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* Used in FIAT-Chrysler, Mercedes, ... */
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#include "../../app.h"
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#define USE_TEST_VECTOR 0
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static const char* test_vector =
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"000000111101010101011010010110010110101001010110100110011001100101010101011010100110100110011010101010101010101010101010101010101010101010101010";
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static bool decode(uint8_t* bits, uint32_t numbytes, uint32_t numbits, ProtoViewMsgInfo* info) {
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if(USE_TEST_VECTOR) { /* Test vector to check that decoding works. */
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bitmap_set_pattern(bits, numbytes, 0, test_vector);
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numbits = strlen(test_vector);
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}
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if(numbits < 64) return false; /* Preamble + data. */
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const char* sync_pattern = "1111010101"
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"01011010";
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uint64_t off = bitmap_seek_bits(bits, numbytes, 0, numbits, sync_pattern);
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if(off == BITMAP_SEEK_NOT_FOUND) return false;
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FURI_LOG_E(TAG, "Schrader TPMS gap+preamble found");
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info->start_off = off;
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off += 10; /* Skip just the long pulse and the first 3 bits of sync, so
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that we have the first byte of data with the sync nibble
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0011 = 0x3. */
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uint8_t raw[8];
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uint8_t id[4];
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uint32_t decoded = convert_from_line_code(
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raw, sizeof(raw), bits, numbytes, off, "01", "10"); /* Manchester code. */
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FURI_LOG_E(TAG, "Schrader TPMS decoded bits: %lu", decoded);
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if(decoded < 64) return false; /* Require the full 8 bytes. */
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raw[0] |= 0xf0; // Fix the preamble nibble for checksum computation.
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uint8_t cksum = crc8(raw, sizeof(raw) - 1, 0xf0, 0x7);
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if(cksum != raw[7]) {
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FURI_LOG_E(TAG, "Schrader TPMS checksum mismatch");
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return false;
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}
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info->pulses_count = (off + 8 * 8 * 2) - info->start_off;
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float kpa = (float)raw[5] * 2.5;
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int temp = raw[6] - 50;
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id[0] = raw[1] & 7;
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id[1] = raw[2];
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id[2] = raw[3];
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id[3] = raw[4];
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fieldset_add_bytes(info->fieldset, "Tire ID", id, 4 * 2);
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fieldset_add_float(info->fieldset, "Pressure kpa", kpa, 2);
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fieldset_add_int(info->fieldset, "Temperature C", temp, 8);
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return true;
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}
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ProtoViewDecoder SchraderTPMSDecoder =
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{.name = "Schrader TPMS", .decode = decode, .get_fields = NULL, .build_message = NULL};
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