Add support for Thermor_a6n_132tx

High nibble checksum investigation done by Qwen3.6 Plus.

Assisted-by: Qwen 3.6 Plus

Author: Jon Klixbuell Langeland

README.md

@@ -386,6 +386,7 @@ See [CONTRIBUTING.md](./docs/CONTRIBUTING.md).
     [298]  TRW TPMS OOK OEM and Clone models
     [299]  TRW TPMS FSK OEM and Clone models
     [300]  Govee Water Leak Detector H5059
+    [301]  Thermor A6N 132TX temperature sensor
 
 * Disabled by default, use -R n or a conf file to enable
 

conf/rtl_433.example.conf

@@ -539,6 +539,7 @@ convert si
   protocol 298 # TRW TPMS OOK OEM and Clone models
   protocol 299 # TRW TPMS FSK OEM and Clone models
   protocol 300 # Govee Water Leak Detector H5059
+  protocol 301 # Thermor A6N 132TX temperature sensor
 
 ## Flex devices (command line option "-X")
 

include/rtl_433_devices.h

@@ -308,6 +308,7 @@
     DECL(tpms_trw_ook) \
     DECL(tpms_trw_fsk) \
     DECL(govee_h5059) \
+    DECL(thermor_a6n_132tx) \
 
     /* Add new decoders here. */
 

src/CMakeLists.txt

@@ -264,6 +264,7 @@ add_library(r_433 STATIC
     devices/thermopro_tx2c.c
     devices/thermopro_tx7b.c
     devices/thermor.c
+    devices/thermor_a6n_132tx.c
     devices/tpms_abarth124.c
     devices/tpms_airpuxem.c
     devices/tpms_ave.c

src/devices/thermor_a6n_132tx.c

@@ -0,0 +1,135 @@
+/** @file
+    Thermor A6N 132TX temperature sensor.
+
+    Copyright (C) 2020 Jon Klixbuell Langeland
+    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"
+
+/**
+Thermor A6N 132TX temperature sensor.
+
+FCC: https://fccid.io/A6N-132TX
+
+32-bit frame, repeated 11 times (look for 5 identical versions).
+
+Data layout:
+
+    IIIICC-- TTTTTTTT TTTTTTTT CCCCCCCC
+
+- I: 4 bit ID
+- C: 2 bit channel
+- -: 2 bit unknown
+- T: 16 bit temperature, stored as int / 10 (e.g. 376 = 37.6C)
+- C: 8 bit checksum
+
+Checksum algorithm:
+- Low nibble: sum of low nibbles of bytes 0-2, mod 16
+- High nibble: ID-specific
+  - ID=4: single bit = (hi_sum + overflow) & 1, upper 3 bits are 0
+    where hi_sum = (b0>>4) + (b1>>4) + (b2>>4)
+    and overflow = low_nibble_sum >> 4
+  - ID=3,5: MSB (bit 3) = parity(b0_lo) XOR parity(b1_lo) XOR parity(b2)
+            lower 3 bits = (2 + (hi_sum & 1)) XOR overflow
+
+Sample data:
+
+    3c 01 7f 3c : 38.3C
+    3c 01 88 a5 : 39.2C
+    3c 01 90 ad : 40.0C
+    50 01 0c bd : 26.8C
+    50 02 03 b5 : 51.5C
+    4c 01 7f 0c : 38.3C (ID=4)
+
+Flex decoder:
+
+    rtl_433 -X 'n=thermor_a6n_132tx,m=OOK_PPM,s=1000,l=2000,g=2000,r=4000,repeats>=5'
+*/
+
+static int thermor_a6n_132tx_decode(r_device *decoder, bitbuffer_t *bitbuffer)
+{
+    int row;
+
+    if (bitbuffer->num_rows == 1 && bitbuffer->bits_per_row[0] == 32) {
+        row = 0;
+    } else {
+        row = bitbuffer_find_repeated_row(bitbuffer, 5, 32);
+        if (row < 0) {
+            return DECODE_ABORT_EARLY;
+        }
+    }
+
+    if (bitbuffer->bits_per_row[row] != 32) {
+        return DECODE_ABORT_LENGTH;
+    }
+
+    uint8_t *b = bitbuffer->bb[row];
+
+    // Checksum low nibble: sum of low nibbles of payload bytes (mod 16)
+    int lo_sum = (b[0] & 0x0f) + (b[1] & 0x0f) + (b[2] & 0x0f);
+    int overflow = lo_sum >> 4;
+    if ((lo_sum & 0x0f) != (b[3] & 0x0f)) {
+        return DECODE_FAIL_MIC;
+    }
+
+    // Checksum high nibble: ID-specific
+    int id = (b[0] >> 4) & 0x0f;
+    int hi_sum = (b[0] >> 4) + (b[1] >> 4) + (b[2] >> 4);
+    int chk_hi = b[3] >> 4;
+
+    if (id == 4) {
+        // ID=4: high nibble is 1 bit, upper 3 bits are 0
+        if (chk_hi != ((hi_sum + overflow) & 1)) {
+            return DECODE_FAIL_MIC;
+        }
+    } else {
+        // ID=3,5: MSB = parity(b0_lo) XOR parity(b1_lo) XOR parity(b2)
+        //         lower 3 bits = (2 + (hi_sum & 1)) XOR overflow
+        int chk_hi_msb = parity8(b[0] & 0x0f) ^ parity8(b[1] & 0x0f) ^ parity8(b[2]);
+        int chk_hi_low = (2 + (hi_sum & 1)) ^ overflow;
+        if (chk_hi != ((chk_hi_msb << 3) | chk_hi_low)) {
+            return DECODE_FAIL_MIC;
+        }
+    }
+
+    int channel = (b[0] >> 2) & 0x03;
+    int temp_raw = (b[1] << 8) | b[2];
+    float temperature_c = temp_raw * 0.1f;
+
+    /* clang-format off */
+    data_t *data = data_make(
+            "model",          "",            DATA_STRING, "Thermor-A6N-132TX",
+            "id",             "ID",          DATA_INT,    id,
+            "channel",        "Channel",     DATA_INT,    channel,
+            "temperature_C",  "Temperature", DATA_FORMAT, "%.1f C", DATA_DOUBLE, temperature_c,
+            "mic",            "Integrity",   DATA_STRING, "CHECKSUM",
+            NULL);
+    /* clang-format on */
+
+    decoder_output_data(decoder, data);
+    return 1;
+}
+
+static char const *const output_fields[] = {
+        "model",
+        "id",
+        "channel",
+        "temperature_C",
+        "mic",
+        NULL,
+};
+
+r_device const thermor_a6n_132tx = {
+        .name        = "Thermor A6N 132TX temperature sensor",
+        .modulation  = OOK_PULSE_PPM,
+        .short_width = 1000,
+        .long_width  = 2000,
+        .gap_limit   = 2000,
+        .reset_limit = 4000,
+        .decode_fn   = &thermor_a6n_132tx_decode,
+        .fields      = output_fields,
+};