Add bm5v2 12V Battery Monitor

tests/bm5v2/readme.md

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+# BM5 v2.0 12V Automotive Battery Monitor
+
+<img src="ancel_bm200.jpg" alt="Ancel BM200" height="240">
+
+Manufactured by Shenzhen Leagend Optoelectronics Co. Ltd.  Sold as "ANCEL BM200" on Amazon, and "QUICKLYNKS BM5-D" on AliExpress
+(I can't find any 3rd party testing reports on this 433mhz model, but this company also produces a popular Bluetooth version called the 
+BM6 among other names, with an FCC-ID of 2AU4A-191114)
+
+The monitor consists of a sensor/transmitter that attaches to the 12v battery, and a solar powered display/receiver that sits on the dash.  The transmitter sends all relevant data, once every 1-2 seconds at 433.92 MHz.
+
+## Signal and Message Format
+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.
+
+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.
+
+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:7d TEMP_SIGN:b V_CUR:16d V_START:16d CHECKSUM:8h
+
+
+
+## Decoding using the `rtl_433` flex spec
+
+`rtl_433 -R 0 -X 'n=bm5v2,m=OOK_PWM,s=227,l=675,r=6000,invert'`
+
+
+
+## Sample Library
+
+| cu8 Sample                                                         | Data Message                       | Decoded Data  |
+|--------------------------------------------------------------------|------------------------------------|--------------------------------------------|
+| [01/bm5v2_d1s1_433.92M_1024k.cu8](01/bm5v2_d1s1_433.92M_1024k.cu8) | {9}800, {88}f154b596c82ca2507b3728 | (Preamble), Device_ID : F154B5 State of Health: 75 %  Cranking System Error: 0  State of Charge: 100 %  Charging System Error: 0  Temperature: 44 C  Current Battery Voltage: 12.90 Starting Voltage: 8.88 |
+| [01/bm5v2_d2s1_433.92M_1024k.cu8](01/bm5v2_d2s1_433.92M_1024k.cu8) | {9}800, {88}f1ac3a91be0a604e734495 | (Preamble), Device_ID : F1AC3A State of Health: 72 % Cranking System Error: 1  State of Charge: 95 %  Charging System Error: 0  Temperature: 10 C  Current Battery Voltage: 12.54  Starting Voltage: 10.95 |
+| [01/bm5v2_d1s2_433.92M_1024k.cu8](01/bm5v2_d1s2_433.92M_1024k.cu8) | {9}800, {88}f154b586c614304ec345e0 | (Preamble), Device_ID : F154B5 State of Health: 67 % Cranking System Error: 0  State of Charge: 99 %  Charging System Error: 0  Temperature: 20 C  Current Battery Voltage: 12.51   Starting Voltage: 11.16 |
+| [01/bm5v2_d1s3_433.92M_250k.cu8](01/bm5v2_d1s3_433.92M_250k.cu8) | {9}800, {88}0eab4a69aefc57b40cbff5 | (Preamble), Device_ID : F154B5 State of Health: 75 % Cranking System Error: 1  State of Charge: 40 %  Charging System Error: 0  Temperature: -1 C  Current Battery Voltage: 12.10 V Starting Voltage: 10.39 V |
+