88ae8f8473
- Change hard coded strings are "const" so any variable pointing to them must also have the const specifier to avoid a warning (from -Wdiscarded-qualifiers) - Change local variables manipulating constant strings must also have the const qualifier - Change hostport_param, fix remaining hostport_param args Co-authored-by: Christian W. Zuckschwerdt <christian@zuckschwerdt.org>
128 lines
4.1 KiB
C
128 lines
4.1 KiB
C
/** @file
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Ecowitt Wireless Outdoor Thermometer WH53/WH0280/WH0281A.
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Copyright 2019 Google LLC.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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*/
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/**
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Ecowitt Wireless Outdoor Thermometer WH53/WH0280/WH0281A.
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55-bit one-row data packet format (inclusive ranges, 0-indexed):
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| 0-6 | 7-bit header, ignored for checksum, always 1111111
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| 7-14 | Model code, 0x53
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| 15-22 | Sensor ID, randomly reinitialized on boot
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| 23-24 | Always 00
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| 25-26 | 2-bit sensor channel, selectable on back of sensor {00=1, 01=2, 10=3}
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| 27-28 | Always 00
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| 29-38 | 10-bit temperature in tenths of degrees C, starting from -40C. e.g. 0=-40C
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| 39-46 | Trailer, always 1111 1111
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| 47-54 | CRC-8 checksum poly 0x31 init 0x00 skipping first 7 bits
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*/
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#include "decoder.h"
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static int ecowitt_decode(r_device *decoder, bitbuffer_t *bitbuffer)
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{
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// All Ecowitt packets have one row.
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if (bitbuffer->num_rows != 1) {
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return DECODE_ABORT_LENGTH;
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}
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// All Ecowitt packets have 55 bits.
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if (bitbuffer->bits_per_row[0] != 55) {
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return DECODE_ABORT_LENGTH;
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}
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uint8_t *row = bitbuffer->bb[0];
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// All Ecowitt packets have the first 7 bits set.
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uint8_t first7bits = row[0] >> 1;
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if (first7bits != 0x7F) {
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return DECODE_ABORT_EARLY;
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}
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// Byte-align the rest of the message by skipping the first 7 bits.
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uint8_t b[6];
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bitbuffer_extract_bytes(bitbuffer, /* row= */ 0, /* pos= */ 7, b, sizeof(b) * 8); // Skip first 7 bits
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// All Ecowitt packets continue with a fixed header
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if (b[0] != 0x53) {
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return DECODE_ABORT_EARLY;
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}
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// Randomly generated at boot time sensor ID.
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int sensor_id = b[1];
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int channel = b[2] >> 4; // First nybble.
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channel++; // Convert 0-indexed wire protocol to 1-indexed channels on the device UI
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if (channel > 3) {
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return DECODE_FAIL_SANITY; // The switch only has 1-3.
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}
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// All Ecowitt packets have bits 27 and 28 set to 0
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// Perhaps these are just an extra two high bits for temperature?
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// The manual though says it only operates to 60C, which about matches 10 bits (1023/10-40C)=62.3C
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// Above 60 is pretty hot - let's just check these are always zero.
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if ((b[2] & (4 | 8)) != 0) {
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return DECODE_ABORT_EARLY;
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}
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// Temperature is next 10 bits
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int temp_raw = ((b[2] & 0x3) << 8) | b[3];
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float temp_c = (temp_raw - 400) * 0.1f;
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// All Ecowitt observed packets have bits 39-48 set.
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if (b[4] != 0xFF) {
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return DECODE_ABORT_EARLY;
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}
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// Compute checksum skipping first 7 bits
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uint8_t wire_crc = b[5];
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int computed_crc = crc8(
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b,
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/* nBytes= */ sizeof(b) - 1, // Exclude the CRC byte itself
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/* polynomial= */ 0x31,
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/* init= */ 0);
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if (wire_crc != computed_crc) {
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return DECODE_FAIL_MIC;
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}
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/* clang-format off */
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data_t *data = data_make(
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"model", "", DATA_STRING, "Ecowitt-WH53",
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"id", "Id", DATA_INT, sensor_id,
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"channel", "Channel", DATA_INT, channel,
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"temperature_C", "Temperature", DATA_FORMAT, "%.01f C", DATA_DOUBLE, temp_c,
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"mic", "Integrity", DATA_STRING, "CRC",
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NULL);
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/* clang-format on */
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decoder_output_data(decoder, data);
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return 1;
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}
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static char const *output_fields[] = {
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"model",
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"id",
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"channel",
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"temperature_C",
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"mic",
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NULL,
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};
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r_device const ecowitt = {
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.name = "Ecowitt Wireless Outdoor Thermometer WH53/WH0280/WH0281A",
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.modulation = OOK_PULSE_PWM,
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.short_width = 500, // 500 us nominal short pulse
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.long_width = 1480, // 1480 us nominal long pulse
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.gap_limit = 1500, // 960 us nominal fixed gap
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.reset_limit = 2000, // 31 ms packet distance (too far apart)
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.sync_width = 0,
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.decode_fn = &ecowitt_decode,
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.fields = output_fields,
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};
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