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https://github.com/Next-Flip/Momentum-Firmware.git
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64 lines
2.1 KiB
C
64 lines
2.1 KiB
C
/* Ford tires TPMS. Usually 443.92 Mhz FSK (in Europe).
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*
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* 52 us short pules
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* Preamble: 0101010101010101010101010101
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* Sync: 0110 (that is 52 us gap + 104 us pulse + 52 us gap)
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* Data: 8 bytes Manchester encoded
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* 01 = zero
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* 10 = one
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*/
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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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const char *sync_pattern = "010101010101" "0110";
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uint8_t sync_len = 12+4; /* We just use 12 preamble symbols + sync. */
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if (numbits-sync_len < 8*8) return false;
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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, "Fort TPMS preamble+sync found");
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info->start_off = off;
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off += sync_len; /* Skip preamble and sync. */
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uint8_t raw[8];
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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, "Ford TPMS decoded bits: %lu", decoded);
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if (decoded < 8*8) return false; /* Require the full 8 bytes. */
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/* CRC is just the sum of the first 7 bytes MOD 256. */
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uint8_t crc = 0;
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for (int j = 0; j < 7; j++) crc += raw[j];
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if (crc != raw[7]) return false; /* Require sane CRC. */
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info->pulses_count = (off+8*8*2) - info->start_off;
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float psi = 0.25 * (((raw[6]&0x20)<<3)|raw[4]);
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/* Temperature apperas to be valid only if the most significant
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* bit of the value is not set. Otherwise its meaning is unknown.
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* Likely useful to alternatively send temperature or other info. */
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int temp = raw[5] & 0x80 ? 0 : raw[5]-56;
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int flags = raw[5] & 0x7f;
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int car_moving = (raw[6] & 0x44) == 0x44;
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fieldset_add_bytes(info->fieldset,"Tire ID",raw,4*2);
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fieldset_add_float(info->fieldset,"Pressure psi",psi,2);
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fieldset_add_int(info->fieldset,"Temperature C",temp,8);
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fieldset_add_hex(info->fieldset,"Flags",flags,7);
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fieldset_add_uint(info->fieldset,"Moving",car_moving,1);
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return true;
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}
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ProtoViewDecoder FordTPMSDecoder = {
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.name = "Ford 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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