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https://github.com/Next-Flip/Momentum-Firmware.git
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62 lines
2.1 KiB
C
62 lines
2.1 KiB
C
/* Citroen TPMS. Usually 443.92 Mhz FSK.
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*
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* Preamble of ~14 high/low 52 us pulses
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* Sync of high 100us pulse then 50us low
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* Then Manchester bits, 10 bytes total.
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* Simple XOR checksum. */
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#include "../../app.h"
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static bool decode(uint8_t *bits, uint32_t numbytes, uint32_t numbits, ProtoViewMsgInfo *info) {
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/* We consider a preamble of 17 symbols. They are more, but the decoding
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* is more likely to happen if we don't pretend to receive from the
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* very start of the message. */
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uint32_t sync_len = 17;
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const char *sync_pattern = "10101010101010110";
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if (numbits-sync_len < 8*10) return false; /* Expect 10 bytes. */
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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, "Renault TPMS preamble+sync found");
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info->start_off = off;
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off += sync_len; /* Skip preamble + sync. */
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uint8_t raw[10];
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uint32_t decoded =
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convert_from_line_code(raw,sizeof(raw),bits,numbytes,off,
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"01","10"); /* Manchester. */
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FURI_LOG_E(TAG, "Citroen TPMS decoded bits: %lu", decoded);
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if (decoded < 8*10) return false; /* Require the full 10 bytes. */
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/* Check the CRC. It's a simple XOR of bytes 1-9, the first byte
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* is not included. The meaning of the first byte is unknown and
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* we don't display it. */
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uint8_t crc = 0;
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for (int j = 1; j < 10; j++) crc ^= raw[j];
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if (crc != 0) return false; /* Require sane checksum. */
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info->pulses_count = (off+8*10*2) - info->start_off;
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int repeat = raw[5] & 0xf;
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float kpa = (float)raw[6]*1.364;
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int temp = raw[7]-50;
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int battery = raw[8]; /* This may be the battery. It's not clear. */
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fieldset_add_bytes(info->fieldset,"Tire ID",raw+1,4*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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fieldset_add_uint(info->fieldset,"Repeat",repeat,4);
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fieldset_add_uint(info->fieldset,"Battery",battery,8);
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return true;
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}
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ProtoViewDecoder CitroenTPMSDecoder = {
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.name = "Citroen TPMS",
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.decode = decode,
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.get_fields = NULL,
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.build_message = NULL
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};
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