Add support for bm5v2

include/rtl_433_devices.h

@@ -282,6 +282,7 @@
     DECL(gridstream192) \
     DECL(gridstream384) \
     DECL(revolt_zx7717) \
+    DECL(bm5) \
 
     /* Add new decoders here. */
 

src/CMakeLists.txt

@@ -65,6 +65,7 @@ add_library(r_433 STATIC
     devices/baldr_rain.c
     devices/blueline.c
     devices/blyss.c
+    devices/bm5.c
     devices/brennenstuhl_rcs_2044.c
     devices/bresser_3ch.c
     devices/bresser_5in1.c

src/devices/bm5.c

@@ -0,0 +1,148 @@
+/** @file
+    bm5-v2 12V Automotive Wireless Battery Monitor.
+
+    Copyright (C) 2025 Cameron Murphy
+
+    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.
+*/
+
+/**
+bm5-v2 12V Automotive Battery Monitor.
+
+Sold as "ANCEL BM200" on Amazon, and "QUICKLYNKS BM5-D" on AliExpress
+
+The sensor transmits a single message, with all relevant data about every 1-2
+seconds at 433.92 MHz,
+
+The transmission is inverted from the normal OOK_PULSE_PWM decoder, with a "0"
+represented as a short pulse of 225us, and a 675us gap, and a "1" represented as
+a long 675us pulse, and a 225us gap.  The implementation below initially
+inverters the buffer to correct for this.
+
+Each message consists of a preamble (long pulse, plus eight 50% symbol length
+pulses) sent at double the normal data rate, then a one byte pause (at regular
+data rate), then ten bytes of payload, plus a one byte Checksum.  The preamble
+is decoded as (0x7F 0x80) by rtl_433 (in the native, non-inverted state) due to
+the initial pulse.
+
+Flex decoder:  `rtl_433 -R 0 -X 'n=bm5-v2,m=OOK_PWM,s=227,l=675,r=6000,invert'`
+
+
+Payload:
+
+- I = 3 byte ID
+- S = 7 bits for battery State of Health (SOH) - 0 to 100 percent
+- C = 1 bit flag for charging system error (!CHARGING on display --probably
+triggered if running voltage below ~13v)
+- s = 7 bits for battery State of Charge (SOC) 0 to 100 percent
+- c = 1 bit flag for cranking system error. (!CRANKING indicator on display -
+triggered if starting voltage drops for too long -- excessive cranking)
+- T = 7 bits for sensor temperature magnitude (degrees C, converted if necessary
+in display)
+- t = 1 bit for temperature sign (0 = positive, 1 = negative)
+- V = 16 bits, little endian for current battery voltage (Voltage is displayed
+as a float with 2 significant digits.  The 16 bit int represents this voltage,
+multiplied by 1600. -- note:  The display truncates the voltages to 2 decimal
+points.  I've chosen to round instead of truncate, as this seems a better
+representation of the true value.)
+- v = 16 bits, little endian for previous low voltage during last start.  (Is
+probably used for the algorithm to determine battery health.  This value will be
+closer to resting voltage for healthy batteries) Same 1600 multiplier as above.
+- R = 1 byte Checksum
+
+    msg:
+IIIIIIIIIIIIIIIIIIIIIIIISSSSSSSCssssssscTTTTTTTtVVVVVVVVVVVVVVVVvvvvvvvvvvvvvvvvRRRRRRRR
+    ID:24h SOH:7d CHARGING:1b SOC:7d CRANKING:1b TEMP:8s V_CUR:16d V_START:16d
+CHECKSUM:8h
+
+*/
+
+#include "decoder.h"
+
+static int bm5_decode(r_device *decoder, bitbuffer_t *bitbuffer)
+{
+    data_t *data;
+    uint8_t b[11];
+
+    bitbuffer_invert(bitbuffer); // This device sends data inverted relative to
+                                 // the OOK_PWM decoder output.
+
+    if (bitbuffer->num_rows != 1) { // Only one message per transmission
+        return DECODE_ABORT_EARLY;
+    }
+
+    // check correct data length
+    if (bitbuffer->bits_per_row[0] != 88) { // 10 bytes data + 1 byte checksum)
+        return DECODE_ABORT_LENGTH;
+    }
+
+    bitbuffer_extract_bytes(bitbuffer, 0, 0, b, sizeof(b) * 8);
+
+    // check for valid checksum
+    if ((unsigned char)add_bytes(&b[0], 10) != b[10]) {
+        return DECODE_FAIL_MIC; // failed checksum - invalid message
+    }
+
+    int id             = (b[0] << 16) | (b[1] << 8) | b[2];
+    int soh            = b[3] >> 1;          // State of Health encoded in 1st 7 bits
+    int charging_error = b[3] & 0x01;        // Charging error flag in bit 8 of byte 4
+    int soc            = b[4] >> 1;          // State pf Charge encoded in 1st 7 bits
+    int cranking_error = b[4] & 0x01;        // Cranking error flag in bit 8 of byte 5
+    int temp           = b[5] >> 1;          // Temperature magnitude in degrees C in first 7 bits of byte 6
+    int temp_sign      = b[5] & 0x01;        // Temperature sign in bit 8 of byte 6
+    int volt1          = (b[7] << 8) | b[6]; // Current voltage
+    int volt2          = (b[9] << 8) | b[8]; // Previous starting voltage
+                                             //
+    if (temp_sign == 1) {
+        temp = -temp; // Invert temp value
+    }
+
+    float battery_volt = volt1 * 0.000625f; // Convert transmitted values to floats.  Rounded to 2
+                                            // decimal places in "data_make" below.
+    float starting_volt = volt2 * 0.000625f;
+
+    /* clang-format off */
+    data = data_make(
+            "model",            "",                       DATA_STRING,   "BM5-v2",
+            "id",               "Device_ID",              DATA_FORMAT,   "%X",            DATA_INT,          id,
+            "health_pct",       "State of Health",        DATA_FORMAT,   "%d %%",         DATA_INT,          soh,
+            "cranking_error",   "Cranking System Error",  DATA_INT,       cranking_error,
+            "charge_pct",       "State of Charge",        DATA_FORMAT,   "%d %%",         DATA_INT,          soc,
+            "charging_error",   "Charging System Error",  DATA_INT,       charging_error,
+            "temperature_C",    "Temperature",            DATA_FORMAT,   "%.1f C",        DATA_DOUBLE,       (float) temp,
+            "battery_V",        "Current Battery Voltage",DATA_FORMAT,   "%.2f V",        DATA_DOUBLE,       battery_volt,
+            "starting_V",       "Starting Voltage",       DATA_FORMAT,   "%.2f V",        DATA_DOUBLE,       starting_volt,
+            "mic",              "Integrity",              DATA_STRING,   "CHECKSUM",
+            NULL);
+    /* clang-format on */
+
+    decoder_output_data(decoder, data);
+    return 1;
+}
+
+static char const *const output_fields[] = {
+        "model",
+        "id",
+        "health_pct",
+        "cranking_error",
+        "charge_pct",
+        "charging_error",
+        "temperature_C",
+        "battery_V",
+        "starting_V",
+        "mic",
+        NULL,
+};
+
+r_device const bm5 = {
+        .name        = "bm5-v2 12V Battery Monitor",
+        .modulation  = OOK_PULSE_PWM,
+        .short_width = 225,
+        .long_width  = 675,
+        .reset_limit = 6000,
+        .decode_fn   = &bm5_decode,
+        .fields      = output_fields,
+};