Python script(s) to read data from Thornwave BT DCPM BlueTooth battery monitor https://www.thornwave.com/.

• Requires functioning BlueTooth stack & gatttool.
• Tested on Raspberry Pi 3b+ Raspbian 5.4 with default BT stack.
• Functions with firmware <= version 2.03 or >2.03 (-X parameter). Newer firmware uses different UUIDs and data formats.
• PowerMeter and ChargeMeter are not properly interpreted when Thornwave is configured with current sign flipped.

Inspiration and data format credit to Stuart Wilde via this forum post:

https://www.irv2.com/forums/f54/thornwave-battery-monitor-375463.html#post4215155

And @tgalarneau for PowerMeter and ChargeMeter on version > 2.03

Setup:

Use bluetoothctl to find BlueTooth MAC address of Thornwave device(s)

sudo bluetoothctl
[bluetooth]# scan on
[NEW] Device D2:07:06:05:CB:1A

Use bluetoothctl 'info' command to check for correct Thornwave.

Test access to Thornwave using gatttool

sudo gatttool -b D2:07:06:05:CB:1A -I -t random
[D2:07:06:05:CB:1A][LE]> connect
Attempting to connect to D2:07:06:05:CB:1A
Connection successful
[D2:07:06:05:CB:1A][LE]> primary
attr handle: 0x0001, end grp handle: 0x0009 uuid: 00001800-0000-1000-8000-00805f9b34fb
attr handle: 0x000a, end grp handle: 0x000d uuid: 00001801-0000-1000-8000-00805f9b34fb
attr handle: 0x000e, end grp handle: 0x0012 uuid: 0000180a-0000-1000-8000-00805f9b34fb
attr handle: 0x0013, end grp handle: 0xffff uuid: 7a95ce00-0ea8-1bcc-71a2-fc7539b81c9c

Verify UUID and handle

[D2:07:06:05:CB:1A][LE]> char-desc
[...lots of stuff...]
handle: 0x0015, uuid: 7a95ce01-0ea8-1bcc-71a2-fc7539b81c9c
[...lots more stuff...]

[D2:07:06:05:CB:1A][LE]> char-read-hnd 0x15
Characteristic value/descriptor: e0 ff 0f c6 51 a6 5b 41 02 b9 4d 41 5b 20 44 40 19 47 28 42 2d ed d7 41 d2 d2 02 00 00 00 00 00 fa 1f 00 00 00 00 00 00 31 70 23 00 a9 d2 0a 0e 91 dc 68 42

The script will read and parse the data in 0x15.

Data Format (Version <= 2.03)):

Fields

 0 - 2:  Unknown
 3    :  Pct Charged, LSB must be stripped
 7 - 4:  V1 volts, LSB, 32-bit float
11 - 8:  V2 volts, LSB, 32-bit float
15 - 12: Current (amps), LSB, 32-bit float
19 - 16: Power (watts), LSB, 32-bit float
23 - 20: Temperature (C), LSB, 32-bit float
31 - 24: Power Meter (watts * 1000), 64-bit int
39 - 32: Charge Meter (Amp-hours * 1000), 64-bit int
43 - 40: Uptime (seconds), unsigned 32-bit int
47 - 44: Date/Time (unknown format)
51 - 48: Peak Current, 32-bit float
52+    : Unknown

Data Format (Version > 2.03)):

Fields

 0 - 4:  Unknown
 8 - 5:  Date/Time Unix Epoc, LSB, 32-bit Uint 
 9 - 12: Unknown
16 - 13: V1 volts, LSB, 32-bit float
20 - 17: V2 volts, LSB, 32-bit float
24 - 21: Current (amps), LSB, 32-bit float
28 - 25: Power (watts), LSB, 32-bit float
36 - 29: Power Meter (watts * 1000), 64-bit int
44 - 37: Charge Meter (Amp-hours * 1000), 64-bit int
48 - 45: Temperature (C), LSB, 32-bit float
48 +   : Unknown

Help:

sudo ./DCPMRead.py -h

usage: DCPMRead.py [-h] -b BLEADDRESS [-P | -H]
Thornwave BT DCPM slurper. Reads and outputs BT DCPM data
optional arguments:
  -h, --help            show this help message and exit
  -b BLEADDRESS, --BLEaddress BLEADDRESS
                        BT DCPM BLE Address
  -P, --Parsable        Machine parsable output (default)
  -H, --Human           Human readable output
  -J, --JSON            JSON output
  -v, --verbose         debug output
  -X, --PowermonX       PowermonX version >2.03 format

To run:

sudo ./DCPMRead.py -b <bluetooth address>

Notes:

• bluetoothctl and gatttool may require sudo privs. The python script may also need sudo privs.
• To create log, run periodically from cron & pipe output to a file with >>