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https://github.com/DarkFlippers/unleashed-firmware
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62 lines
2.3 KiB
C
62 lines
2.3 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 variant EG53MA4 TPMS.
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* Usually 443.92 Mhz OOK, 100us pulse len.
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*
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* Preamble: alternating pulse/gap, 100us.
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* Sync (as pulses and gaps): "01100101", already part of the data stream
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* (first nibble) corresponding to 0x4
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*
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* A total of 10 bytes payload, Manchester encoded.
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*
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* 0 = 01
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* 1 = 10
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*
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* Used in certain Open cars and others.
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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"
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"01100101";
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uint8_t sync_len = 12 + 8; /* We just use 12 preamble symbols + sync. */
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if(numbits - sync_len + 8 < 8 * 10) 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, "Schrader EG53MA4 TPMS preamble+sync found");
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info->start_off = off;
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off += sync_len - 8; /* Skip preamble, not sync that is part of the data. */
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uint8_t raw[10];
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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 EG53MA4 TPMS decoded bits: %lu", decoded);
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if(decoded < 10 * 8) return false; /* Require the full 10 bytes. */
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/* CRC is just all bytes added mod 256. */
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uint8_t crc = 0;
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for(int j = 0; j < 9; j++) crc += raw[j];
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if(crc != raw[9]) return false; /* Require sane CRC. */
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info->pulses_count = (off + 10 * 8 * 2) - info->start_off;
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/* To convert the raw pressure to kPa, RTL433 uses 2.5, but is likely
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* wrong. Searching on Google for users experimenting with the value
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* reported, the value appears to be 2.75. */
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float kpa = (float)raw[7] * 2.75;
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int temp_f = raw[8];
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int temp_c = (temp_f - 32) * 5 / 9; /* Convert Fahrenheit to Celsius. */
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fieldset_add_bytes(info->fieldset, "Tire ID", raw + 4, 3 * 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_c, 8);
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return true;
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}
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ProtoViewDecoder SchraderEG53MA4TPMSDecoder =
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{.name = "Schrader EG53MA4 TPMS", .decode = decode, .get_fields = NULL, .build_message = NULL};
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