Add Inkbird ITH-20R support

Author: Dmitriy Kozyrev
Provides decoding for the Inkbird ITH-20R temperature and humidity sensors.
These sensors have an exceptionally long preamble which required increasing the size of the bitbuffer and the FSK pulse detection max length substantially.

README.md

@@ -277,6 +277,7 @@ See [CONTRIBUTING.md](./docs/CONTRIBUTING.md).
     [191]  Markisol, E-Motion, BOFU, Rollerhouse, BF-30x, BF-415 curtain remote
     [192]  Govee Water Leak Dectector H5054, Door Contact Sensor B5023
     [193]  Clipsal CMR113 Cent-a-meter power meter
+    [194]  Inkbird ITH-20R temperature humidity sensor
 
 * Disabled by default, use -R n or -G
 

conf/rtl_433.example.conf

@@ -414,6 +414,7 @@ stop_after_successful_events false
   protocol 191 # Markisol, E-Motion, BOFU, Rollerhouse, BF-30x, BF-415 curtain remote
   protocol 192 # Govee Water Leak Dectector H5054, Door Contact Sensor B5023
   protocol 193 # Clipsal CMR113 Cent-a-meter power meter
+  protocol 194 # Inkbird ITH-20R temperature humidity sensor
 
 ## Flex devices (command line option "-X")
 

include/rtl_433_devices.h

@@ -201,6 +201,7 @@
     DECL(markisol) \
     DECL(govee) \
     DECL(cmr113) \
+    DECL(inkbird_ith20r) \
 
     /* Add new decoders here. */
 

src/CMakeLists.txt

@@ -111,6 +111,7 @@ add_library(r_433 STATIC
     devices/ibis_beacon.c
     devices/ikea_sparsnas.c
     devices/infactory.c
+    devices/inkbird_ith20r.c
     devices/inovalley-kw9015b.c
     devices/insteon.c
     devices/interlogix.c

src/devices/inkbird_ith20r.c

@@ -0,0 +1,165 @@
+/** @file
+    Decoder for Inkbird ITH-20R.
+
+    Copyright (C) 2020 Dmitriy Kozyrev
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+*/
+
+/**
+Decoder for Inkbird ITH-20R.
+
+https://www.ink-bird.com/products-data-logger-ith20r.html
+
+The compact 3-in-1 multifunction outdoor sensor transmits the data on 433.92 MHz.
+The device uses FSK-PCM encoding,
+The device sends a transmission every ~80 sec.
+
+Decoding borrowed from https://groups.google.com/forum/#!topic/rtl_433/oeExmwoBI0w
+
+- Total packet length 14563 bits:
+- Preamble: aa aa aa ... aa aa (14400 on-off sync bits)
+- Sync Word (16 bits): 2DD4
+- Data (147 bits):
+- Byte    Sample      Comment
+- 0-2     D3910F      Always the same across devices, a device type?
+- 3       00          00 - normal work , 40 - unlink sensor (button pressed 5s), 80 - battery replaced
+- 4       01          Changes from 1 to 2 if external sensor present
+- 5-6     0301        Unknown (also seen 0201), sw version?
+- 7       58          Battery % 0-100
+- 8-9     A221        Device id, always the same for a sensor but each sensor is different
+- 10-11   D600        Temperature in C * 10, little endian, so 0xD200 is 210, 21.0C or 69.8F
+- 12-13   F400        Temperature C * 10 for the external sensor,  0x1405 if not connected
+- 14-15   D301        Relative humidity %  * 10, little endian, so 0xC501 is 453 or 45.3%
+- 16-17   38FB        CRC16
+- 18      0           Unknown 3 bits (seen 0 and 2)
+
+CRC16 (bytes 0-15), without sync word):
+poly=0x8005  init=0x2f61  refin=true  refout=true  xorout=0x0000  check=0x3583  residue=0x0000
+
+To look at unknown data fields run with -vv key.
+
+Decoder written by Dmitriy Kozyrev, 2020
+*/
+
+#include "decoder.h"
+
+static const uint8_t preamble_pattern[] = { 0xaa, 0xaa, 0xaa, 0x2d, 0xd4 };
+
+#define INKBIRD_ITH20R_CRC_POLY 0xA001  // reflected 0x8005
+#define INKBIRD_ITH20R_CRC_INIT 0x86F4  // reflected 0x2f61
+
+
+static int inkbird_ith20r_callback(r_device *decoder, bitbuffer_t *bitbuffer)
+{
+    data_t *data;
+    uint8_t msg[19];
+
+    if ( (bitbuffer->num_rows != 1)
+         || (bitbuffer->bits_per_row[0] < 187)
+          /*|| (bitbuffer->bits_per_row[0] > 14563)*/ ) {
+        if (decoder->verbose > 1) {
+            fprintf(stderr, "%s bit_per_row %u out of range\n", __func__, bitbuffer->bits_per_row[0]);
+        }
+        return DECODE_ABORT_LENGTH; // Unrecognized data
+    }
+
+    unsigned start_pos = bitbuffer_search(bitbuffer, 0, 0,
+            preamble_pattern, sizeof (preamble_pattern) * 8);
+
+    if (start_pos == bitbuffer->bits_per_row[0]) {
+        return DECODE_FAIL_SANITY;  // Not found preamble
+    }
+
+    start_pos += sizeof (preamble_pattern) * 8;
+    unsigned len = bitbuffer->bits_per_row[0] - start_pos;
+
+    if (decoder->verbose > 1) {
+        fprintf(stderr, "%s start_pos=%u\n", __func__, start_pos);
+        fprintf(stderr, "%s len=%u\n", __func__, len);
+    }
+
+    if (((len + 7) / 8) < sizeof (msg)) {
+        if (decoder->verbose) {
+            fprintf(stderr, "%s %u too short\n", __func__, len);
+        }
+        return DECODE_ABORT_LENGTH; // Message too short
+    }
+    // truncate any excessive bits
+    len = MIN(len, sizeof (msg) * 8);
+
+    bitbuffer_extract_bytes(bitbuffer, 0, start_pos, msg, len);
+
+    // CRC check
+    uint16_t crc_calculated = crc16lsb(msg, 16, INKBIRD_ITH20R_CRC_POLY, INKBIRD_ITH20R_CRC_INIT);
+    uint16_t crc_received = msg[17] << 8 | msg[16];
+
+    if (decoder->verbose > 1) {
+        fprintf(stderr, "%s CRC 0x%04X = 0x%04X\n", __func__, crc_calculated, crc_received);
+    }
+
+    if (crc_received != crc_calculated) {
+        if (decoder->verbose) {
+            fprintf(stderr, "%s CRC check failed (0x%04X != 0x%04X)\n", __func__, crc_calculated, crc_received);
+        }
+        return DECODE_FAIL_MIC;
+    }
+
+    uint32_t subtype = (msg[3] << 24 | msg[2] << 16 | msg[1] << 8 | msg[0]);
+    int sensor_num = msg[4];
+    uint16_t word56 = (msg[6] << 8 | msg[5]);
+    int battery = msg[7];
+    uint16_t sensor_id = (msg[9] << 8 | msg[8]);
+    float temperature = (float)((int16_t)(msg[11] << 8 | msg[10])) / 10.0;
+    float temperature_ext = (float)((int16_t)(msg[13] << 8 | msg[12])) / 10.0;
+    float humidity = (float)(msg[15] << 8 | msg[14]) / 10.0;
+    uint8_t word18 = msg[18];
+
+    if (decoder->verbose) {
+        fprintf(stderr, "%s dword0-3= 0x%08X\n", __func__, subtype);
+        fprintf(stderr, "%s word5-6= 0x%04X\n", __func__, word56);
+        fprintf(stderr, "%s byte18= 0x%02X\n", __func__, word18);
+    }
+
+    data = data_make(
+            "model",            "",             DATA_STRING, "Inkbird ITH-20R",
+            "id",               "",             DATA_INT,    sensor_id,
+            "battery",          "Battery",      DATA_INT,    battery,
+            "sensor_num",       "",             DATA_INT,    sensor_num,
+            "mic",              "Integrity",    DATA_STRING, "CRC",
+            "temperature_C",    "Temperature",  DATA_FORMAT, "%.1f C", DATA_DOUBLE, temperature,
+            "temperature2_C",   "Temperature2", DATA_FORMAT, "%.1f C", DATA_DOUBLE, temperature_ext,
+            "humidity",         "Humidity",     DATA_FORMAT, "%.1f %%", DATA_DOUBLE, humidity,
+            NULL);
+
+    decoder_output_data(decoder, data);
+
+    return 1;
+}
+
+static char *output_fields[] = {
+    "model",
+    "id",
+    "battery",
+    "sensor_num",
+    "mic",
+    "temperature_C",
+    "temperature2_C",
+    "humidity",
+    NULL
+};
+
+r_device inkbird_ith20r = {
+    .name          = "Inkbird ITH-20R temperature humidity sensor",
+    .modulation    = FSK_PULSE_PCM,
+    .sync_width    = 0,     // No sync bit used
+    .short_width   = 100,   // Width of a '0' gap
+    .long_width    = 100,   // Width of a '1' gap
+    .reset_limit   = 4000,  // Maximum gap size before End Of Message [us]
+    .decode_fn     = &inkbird_ith20r_callback,
+    .disabled      = 0,
+    .fields        = output_fields,
+};

vs15/rtl_433.vcxproj

@@ -240,6 +240,7 @@ COPY ..\..\libusb\MS64\dll\libusb*.dll $(TargetDir)</Command>
     <ClCompile Include="..\src\devices\ibis_beacon.c" />
     <ClCompile Include="..\src\devices\ikea_sparsnas.c" />
     <ClCompile Include="..\src\devices\infactory.c" />
+    <ClCompile Include="..\src\devices\inkbird_ith20r.c" />
     <ClCompile Include="..\src\devices\inovalley-kw9015b.c" />
     <ClCompile Include="..\src\devices\insteon.c" />
     <ClCompile Include="..\src\devices\interlogix.c" />

vs15/rtl_433.vcxproj.filters

@@ -457,6 +457,9 @@
     <ClCompile Include="..\src\devices\infactory.c">
       <Filter>Source Files\devices</Filter>
     </ClCompile>
+    <ClCompile Include="..\src\devices\inkbird_ith20r.c">
+      <Filter>Source Files\devices</Filter>
+    </ClCompile>
     <ClCompile Include="..\src\devices\inovalley-kw9015b.c">
       <Filter>Source Files\devices</Filter>
     </ClCompile>