src/devices/schraeder.c

   1 /* Schraeder TPMS protocol
   2  *
   3  * Copyright © 2016 Benjamin Larsson
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  */
  10
  11 /**
  12  * Packet payload: 8,5 bytes, 17 nibbles
  13  *
  14  *           01 23 45 67 89 AB CD EF 0
  15  * [00] {68} 7f 67 03 a3 8b 20 04 94 9
  16  *           SP UU UI II II IU UU UC C
  17  *
  18  * S = sync
  19  * P = preamble (0xf)
  20  * U = unknown
  21  * I = id
  22  * C = CRC8 from nibble 1 to E
  23  */
  24
  25 #include "rtl_433.h"
  26 #include "pulse_demod.h"
  27 #include "util.h"
  28
  29
  30 static int schraeder_callback(bitbuffer_t *bitbuffer) {
  31         char time_str[LOCAL_TIME_BUFLEN];
  32         bitrow_t *bb = bitbuffer->bb;
  33         uint32_t serial_id = 0;
  34         data_t *data;
  35         char hexid[20] = {0};
  36         uint8_t work_buffer[9];
  37         int i;
  38
  39         /* Reject wrong amount of bits */
  40         if ( bitbuffer->bits_per_row[0] != 68)
  41                 return 0;
  42
  43         /* shift the buffer 4 bits for the crc8 calculation */
  44         for (i=0 ; i<8 ; i++)
  45                 work_buffer[i] = (bb[0][i]&0x0F)<<4 | (bb[0][i+1]&0xF0) >> 4;
  46
  47         /* Calculate the crc */
  48         if (work_buffer[7] != crc8(work_buffer, 7, 0x07, 0xf0)) {
  49                 return 0;
  50         }
  51
  52         local_time_str(0, time_str);
  53
  54         /* Get serial number id */
  55         serial_id = (bb[0][2]&0x0F) << 20 | bb[0][3] << 12 | bb[0][4] << 4 | (bb[0][5]&0xF0) >> 4;
  56         sprintf(hexid, "%X", serial_id);
  57
  58         if (debug_output >= 1) {
  59                 fprintf(stderr, "Schraeder TPMS decoder\n");
  60                 bitbuffer_print(bitbuffer);
  61                 fprintf(stderr, "id = 0x%X\n", serial_id);
  62                 fprintf(stderr, "CRC = %x\n", crc8(work_buffer, 7, 0x07, 0xf0));
  63         }
  64
  65         data = data_make("time", "", DATA_STRING, time_str,
  66                                         "model", "", DATA_STRING, "Schraeder",
  67                                         "type", "", DATA_STRING, "TPMS",
  68                                         "id", "ID", DATA_STRING, hexid,
  69                                         "crc", "", DATA_STRING, "OK",
  70                                         NULL);
  71
  72         data_acquired_handler(data);
  73         return 0;
  74 }
  75
  76 static char *output_fields[] = {
  77         "time",
  78         "model",
  79         "id",
  80         "flags",
  81         "pressure",
  82         "temperature_C",
  83         "depth",
  84         NULL
  85 };
  86
  87 r_device schraeder = {
  88         .name                   = "Schraeder TPMS",
  89         .modulation             = OOK_PULSE_MANCHESTER_ZEROBIT,
  90         .short_limit    = 30*4,
  91         .long_limit     = 0,
  92         .reset_limit    = 120*4,
  93         .json_callback  = &schraeder_callback,
  94         .disabled               = 0,
  95         .fields                 = output_fields,
  96 };