Add support for Ecowitt temperature sensor

conf/rtl_433.example.conf

@@ -312,6 +312,7 @@ stop_after_successful_events false
   protocol 124 # LaCrosse/ELV/Conrad WS7000/WS2500 weather sensors
   protocol 125 # TS-FT002 Wireless Ultrasonic Tank Liquid Level Meter With Temperature Sensor
   protocol 126 # Companion WTR001 Temperature Sensor
+  protocol 127 # Ecowitt Wireless Outdoor Thermometer WH53/WH0280/WH0281A
 
 ## Flex devices (command line option "-X")
 

include/r_device.h

@@ -21,13 +21,16 @@ enum modulation_types {
     FSK_PULSE_MANCHESTER_ZEROBIT = 18, ///< FSK, Manchester encoding.
 };
 
-/** Decoders should return n>=0 for n packets successfully decoded,
+/** Decoders should return n>0 for n packets successfully decoded,
     an ABORT code if the bitbuffer is no applicable,
     or a FAIL code if the message is malformed. */
 enum decode_return_codes {
+    DECODE_SUCCESS      = 1,
     DECODE_FAIL_OTHER   = 0, ///< legacy, do not use
+    /** Bitbuffer row count or row length is wrong for this sensor. */
     DECODE_ABORT_LENGTH = -1,
     DECODE_ABORT_EARLY  = -2,
+    /** Message Integrity Check failed: e.g. checksum/CRC doesn't validate. */
     DECODE_FAIL_MIC     = -3,
     DECODE_FAIL_SANITY  = -4,
 };

include/rtl_433_devices.h

@@ -134,6 +134,7 @@
     DECL(lacrosse_ws7000) \
     DECL(ts_ft002) \
     DECL(companion_wtr001) \
+    DECL(ecowitt) \
     /* Add new decoders here. */
 
 #define DECL(name) extern r_device name;

src/CMakeLists.txt

@@ -45,6 +45,7 @@ add_executable(rtl_433
 	devices/digitech_xc0324.c
 	devices/dish_remote_6_3.c
 	devices/dsc.c
+	devices/ecowitt.c
 	devices/efergy_e2_classic.c
 	devices/efergy_optical.c
 	devices/elro_db286a.c

src/Makefile.am

@@ -46,6 +46,7 @@ rtl_433_SOURCES      = abuf.c \
                        devices/digitech_xc0324.c \
                        devices/dish_remote_6_3.c \
                        devices/dsc.c \
+                       devices/ecowitt.c \
                        devices/efergy_e2_classic.c \
                        devices/efergy_optical.c \
                        devices/elro_db286a.c \

src/devices/ecowitt.c

@@ -0,0 +1,119 @@
+/*
+ * 55-bit one-row data packet format (inclusive ranges, 0-indexed):
+ * |  0-6  | 7-bit header, ignored for checksum, always 1111111
+ * |  7-14 | Always 01010011
+ * | 15-22 | Sensor ID, randomly reinitialized on boot
+ * | 23-24 | Always 00
+ * | 25-26 | 2-bit sensor channel, selectable on back of sensor {00=1, 01=2, 10=3}
+ * | 27-28 | Always 00
+ * | 29-38 | 10-bit temperature in tenths of degrees C, starting from -40C. e.g. 0=-40C
+ * | 39-46 | Trailer, always 1111 1111
+ * | 47-54 | CRC-8 checksum poly 0x31 init 0x00 skipping first 7 bits
+ * 
+ * Copyright 2019 Google LLC.
+ * 
+ * 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.
+ */
+#include "decoder.h"
+
+static int ecowitt_decode(r_device *decoder, bitbuffer_t *bitbuffer) {
+    // All Ecowitt packets have one row.
+    if (bitbuffer->num_rows != 1) {
+        return DECODE_ABORT_LENGTH;
+    }
+
+    // All Ecowitt packets have 55 bits.
+    if (bitbuffer->bits_per_row[0] != 55) {
+        return DECODE_ABORT_LENGTH;
+    }
+
+    uint8_t *row = bitbuffer->bb[0];
+
+    // All Ecowitt packets have the first 7 bits set.
+    uint8_t first7bits = row[0] >> 1;
+    if (first7bits != 0x7F) {
+        return DECODE_ABORT_EARLY;
+    }
+
+    // Byte-align the rest of the message by skipping the first 7 bits.
+    uint8_t b[6];
+    bitbuffer_extract_bytes(bitbuffer, /* row= */ 0, /* pos= */ 7, b, sizeof(b) * 8); // Skip first 7 bits
+
+    // All Ecowitt packets continue with a fixed header
+    if (b[0] != 0x53) {
+        return DECODE_ABORT_EARLY;
+    }
+
+    // Randomly generated at boot time sensor ID.
+    int sensorID = b[1];
+
+    int channel = b[2] >> 4;  // First nybble.
+    channel++; // Convert 0-indexed wire protocol to 1-indexed channels on the device UI
+    if (channel < 1 || channel > 3) {
+        return DECODE_FAIL_SANITY;  // The switch only has 1-3.
+    }
+
+    // All Ecowitt packets have bits 27 and 28 set to 0
+    // Perhaps these are just an extra two high bits for temperature?
+    // The manual though says it only operates to 60C, which about matches 10 bits (1023/10-40C)=62.3C
+    // Above 60 is pretty hot - let's just check these are always zero.
+    if ((b[2] & (4 | 8)) != 0) {
+        return DECODE_ABORT_EARLY;
+    }
+
+    // Temperature is next 10 bits
+    float tempC    = -40.0;  // Bias
+    tempC += (float) b[3] / 10.0;
+    tempC += (float) ((b[2] & 0x3) << 8) / 10.0;
+
+    // All Ecowitt observed packets have bits 39-48 set.
+    if (b[4] != 0xFF) {
+        return DECODE_ABORT_EARLY;
+    }
+
+    // Compute checksum skipping first 7 bits
+    uint8_t wireCRC = b[5];
+    int computedCRC = crc8(
+        b,
+        /* nBytes= */ sizeof(b)-1, // Exclude the CRC byte itself
+        /* polynomial= */ 0x31,
+        /* init= */ 0);
+    if (wireCRC != computedCRC) {
+        return DECODE_FAIL_MIC;
+    }
+
+    data_t *data = data_make(
+            "model", "", DATA_STRING, "Ecowitt-WH53",
+            "id", "Id", DATA_INT, sensorID,
+            "channel", "Channel", DATA_INT, channel,
+            "temperature_C", "Temperature", DATA_FORMAT, "%.01f C", DATA_DOUBLE, tempC,
+            "mic", "Integrity", DATA_STRING, "CRC",
+            NULL);
+    decoder_output_data(decoder, data);
+    return DECODE_SUCCESS;
+}
+
+static char *output_fields[] = {
+        "model",
+        "id",
+        "channel",
+        "temperature_C",
+        "mic",
+        NULL
+};
+
+r_device ecowitt = {
+        .name        = "Ecowitt Temperature Sensor",
+        .modulation  = OOK_PULSE_PWM, // copied from output, OOK_PWM = OOK_PULSE_PWM
+        .short_width = 504,           // copied from output
+        .long_width  = 1480,          // copied from output
+        .gap_limit   = 4800,          // guessing, copied from generic_temperature_sensor
+        .reset_limit = 968,           // copied from output
+        .sync_width  = 0,             // copied from output
+        .decode_fn   = &ecowitt_decode,
+        .disabled    = 0,
+        .fields      = output_fields,
+};

vs15/rtl_433.vcxproj

@@ -158,6 +158,7 @@
     <ClCompile Include="..\src\devices\digitech_xc0324.c" />
     <ClCompile Include="..\src\devices\dish_remote_6_3.c" />
     <ClCompile Include="..\src\devices\dsc.c" />
+    <ClCompile Include="..\src\devices\ecowitt.c" />
     <ClCompile Include="..\src\devices\efergy_e2_classic.c" />
     <ClCompile Include="..\src\devices\efergy_optical.c" />
     <ClCompile Include="..\src\devices\elro_db286a.c" />
@@ -249,4 +250,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>

vs15/rtl_433.vcxproj.filters

@@ -235,6 +235,9 @@
     <ClCompile Include="..\src\devices\dsc.c">
       <Filter>Source Files\devices</Filter>
     </ClCompile>
+    <ClCompile Include="..\src\devices\ecowitt.c">
+      <Filter>Source Files\devices</Filter>
+    </ClCompile>
     <ClCompile Include="..\src\devices\efergy_e2_classic.c">
       <Filter>Source Files\devices</Filter>
     </ClCompile>
@@ -494,4 +497,4 @@
       <Filter>Source Files\devices</Filter>
     </ClCompile>
   </ItemGroup>
-</Project>
+</Project>