OWON Bluetooth Meters on Linux

Linux CLI Support for B35T+, B41T+, OW18E, CM2100B

Captures, converts, displays and stores Bluetooth (BLE) output from these meters.

Requirements

gatttool needs to be installed and operational in linux for this application to work.

Setup

1) Build owon_multi_cli

$ make


2) Find the multimeter (string should be BDM):

$ sudo hcitool lescan
62:9C:C3:39:99:2F (unknown)
56:E2:58:23:66:3F (unknown)
34:49:51:A5:9C:C7 (unknown)
A6:C0:80:94:54:D9 BDM
40:CB:C0:E3:15:7B (unknown)
5C:02:EA:FB:05:68 (unknown)
76:EA:A1:21:72:2A (unknown)
6B:CE:24:60:40:31 (unknown)

or try using this discovery tool:

$ python3 -u ./py-ble-scan2.py
A6:C0:80:94:54:D9 BDM

If your hci0 (or ble stack) is stuck, try resetting via:

$ sudo python3 -u ./hci-resetter.py --now
Resetting HCI hci0
HCI hci0 has been reset


3) Run the app with the multimeter address as the first parameter, 
   and the meter type as the second:

$ sudo ./owon_multi_cli -a A6:C0:80:94:54:D9 -t cm2100b

(by default, you'll likely have to run this under sudo because the gatttool
won't seem to talk to BLE devices initially without being superuser/root)


4) If you want to see the raw hex bytes (from linux cli):

$ gatttool -b A6:C0:80:E5:84:0C -I
[A6:C0:80:E5:84:0C][LE]> connect
Attempting to connect to A6:C0:80:E5:84:0C
Connection successful
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
Notification handle = 0x001b value: 24 f0 04 00 00 00 
[A6:C0:80:E5:84:0C][LE]> quit

* Use your device's BLE MAC address.  
* The 0x001b value may be the same or it may be different for you.  
* If your (new) meter shows a different handle id, 
  you can try to edit the source code and see if the application decodes your stream.  
* Run the application with "-d" switch for debugging output.

Usage

$ sudo ./owon_multi_cli

Usage: ./owon_multi_cli  -a <address> -t b35t|b41t|cm2100b|ow18e [-l <filename>] [-d] [-q]
-h: This help
-a <address>: Set the address of the cm2100b meter, eg, -a 98:84:E3:CD:C0:E5
-t b35t|b41t|cm2100b|ow18e: Which model of meter
-l <filename>: Log text output to a file
-d: debug enabled
-j: json output
-q: quiet output
-1: run once (one data point) and then exit

Example

Run the application, sending output to stdout, and also log to a file.

Timestamps are unix epoch with 2-digit fractional seconds. Numeric field
follows, then meter mode token strings.

$ sudo ./owon_multi_cli -a A6:C0:80:94:54:D9 -t cm2100b -l foo.out
1699308108.32 00.00 DC mV
1699308108.58 -0.01 DC mV
1699308109.11 -0.01 DC mV
1699308109.66 -0.01 DC mV
1699308110.18 -0.01 DC mV
1699308110.39 00.00 DC mV
1699308110.89 00.00 DC mV
1699308111.39 00.00 DC mV
1699308111.92 00.00 DC mV
1699308112.21 -0.01 DC mV
1699308112.42 00.00 DC mV

Here is a run with json style output:

$ sudo ./owon_multi_cli -a A6:C0:80:E5:84:0C -t ow18e -j
{ "Timestamp": "1706211070.13", "Display_Value": "2.390 K Ohms" }
{ "Timestamp": "1706211070.63", "Display_Value": "2.390 K Ohms" }
{ "Timestamp": "1706211071.13", "Display_Value": "2.390 K Ohms" }
{ "Timestamp": "1706211071.65", "Display_Value": "2.390 K Ohms" }
{ "Timestamp": "1706211072.18", "Display_Value": "2.390 K Ohms" }


Run the application just once and exit.  Show examples with both json and text:

$ sudo ./owon_multi_cli -a A6:C0:80:94:54:D9 -t cm2100b -1
1706753314.87 04.95 Ohms

$ sudo ./owon_multi_cli -a A6:C0:80:94:54:D9 -t cm2100b -1 -j
{ "Timestamp": "1706753412.52", "Display_Value": "1.0059 K Ohms" }

Unit Testing

Run the application in debug and json mode and save its output to a file.

$ sudo ./owon_multi_cli -a A6:C0:80:E5:84:0C -t ow18e -j -d > ow18e-ref-data-ohms.txt
{ "BLE_bytes" : "[2b, f1, 04, 00, 56, 09]", "Function": "00000100", "Scale": "05", "Decimal": "03", "Measurement": "2390", "Timestamp": "1706210330.73", "Display_Value": "2.390 K Ohms" }
{ "BLE_bytes" : "[2b, f1, 04, 00, 56, 09]", "Function": "00000100", "Scale": "05", "Decimal": "03", "Measurement": "2390", "Timestamp": "1706210331.23", "Display_Value": "2.390 K Ohms" }
{ "BLE_bytes" : "[2b, f1, 04, 00, 56, 09]", "Function": "00000100", "Scale": "05", "Decimal": "03", "Measurement": "2390", "Timestamp": "1706210331.73", "Display_Value": "2.390 K Ohms" }


There is a helper python script "wrap_json_lines.py" that can take the raw json lines from the 
cli output and wrap them into a fully parsable json block:

$ ./wrap_json_lines.py -f ow18e-ref-data-ohms.txt  | python -mjson.tool

[
     {
     "BLE_bytes": "[2a, f1, 04, 00, af, 08]",
     "Function": "00000100",
     "Scale": "05",
     "Decimal": "02",
     "Measurement": "2223",
     "Timestamp": "1706209552.45",
     "Display_Value": "22.23 K Ohms"
     },
     {
     "BLE_bytes": "[2a, f1, 04, 00, af, 08]",
     "Function": "00000100",
     "Scale": "05",
     "Decimal": "02",
     "Measurement": "2223",
     "Timestamp": "1706209552.97",
     "Display_Value": "22.23 K Ohms"
     },
     {
     "BLE_bytes": "[2a, f1, 04, 00, af, 08]",
     "Function": "00000100",
     "Scale": "05",
     "Decimal": "02",
     "Measurement": "2223",
     "Timestamp": "1706209553.50",
     "Display_Value": "22.23 K Ohms"
     }
]

Hint on Linux Line Buffering

Do you know about the 'stdbuf' command?  Try something like this, if your output is 'laggy':

$ stdbuf -o0 ./owon_multi_cli -a A6:C0:80:94:54:D9 -t cm2100b -j -d | tee cm2100b-ref-data-ohms.txt

stdbuf with '-o0' is about output buffering.  This method, when run before your main cli command,
will disable the internal buffering of the operating system.

Also, note that for python apps, there is a different method that must be used.  Use the '-u' switch
and run python3 (the interpreter) directly as:

$ python3 -u some_python_app.py

and that will enable more real-time stdout buffering with python.

a-v-s/Owon-Multimeters

OWON Bluetooth Meters on Linux

Linux CLI Support for B35T+, B41T+, OW18E, CM2100B

Requirements

Setup

Usage

Example

Unit Testing

Hint on Linux Line Buffering

Resources