deancording / owonb35

Bluetooth Client for Owon B35 Multimeter

owonb35

Bluetooth Client for Owon B35 Multimeter for newer (post mid 2017) multimeters with the Semic CS7729CN-001 chip.

Older multimeters that use the Fortune Semiconductor FS9922 chip should use inflex/owon-b35.

The Owon B35 series of multimeters use Bluetooth Low Energy (BLE) to transmit readings to remote monitors such as smartphone apps. This Linux client allows to to caputure measurement data to you computer to record in a file or display on charting software such as gnuplot or KST.

Requirements

This client requires the Gattlib BLE library to be installed. Compiled packages are available to install without needing to compile.

Installation

Either download the compiled binary or the source code to compile your own.

Compiling is a simple make.

Usage

The client is designed to be a simple receiver of measurement data that outputs in formats that can be piped into other tools for processing or display.

owonb35 [-s|-S|-t|-T|-d] [-c|-j] [-n|-u|-m|-b|-k|-M] [-x] [-r] [-q] [-h|-V] [<device_address>]
        Measurement collection
        
owonb35 -R <seconds per measurement> <number of measurements> [<device_address>]
        Start offline measurement recording

        Client for Owon B35/B35+/B35T+ digital multimeters using bluetooth.

        -i               Interactive remote control
        -s               Timestamp measurements in elapsed seconds from first reading
        -S               Timestamp measurements in Unix epoch seconds
        -t               Timestamp measurements in elapsed milliseconds from first reading
        -T               Timestamp measurements in Javascript epoch milliseconds
        -d               Timestamp measurements with ISO date/time
        -c               Comma separated values (CSV) output
        -j               JSON output
        -n               Scale measurements to nano units
        -u               Scale measurements to micro units
        -m               Scale measurements to milli units
        -b               Scale measurements to base units
        -k               Scale measurements to kilo units
        -M               Scale measurements to mega units
        -x               Output measurement value without units or type for use with feedgnuplot
        -R               Start offline measurement recording
        -r               Download offline measurement recording
        -q               Quiet - no status output
        -h               Display this help and exit
        -V               Display version and exit
        <device_address> Address of Owon multimeter to connect
                          otherwise will connect to first meter found if not specified

        Interactive controls:
                s - Select
                a - Auto
                r - Range
                l - Backlight
                h - Hold
                b - Turn off Bluetooth
                d - Delta (Relative)
                f - Fequency Hz/Duty
                m - Min/Max
                n - Normal display

You can provide an optional Bluetooth address for the specific multimeter to connect to or the client will otherwise scan for devices and connect to the first multimeter it finds. Scanning and connection can be a bit flaky at times. Note that only one client can connect to the multimeter at a time.

Measurments can be optionally timestamped in actual time or elapsed time since the first measurement was received. Timestamps can be in seconds, milliseconds, or date-time. Note that the multimeter transmits measurements approximately every 600ms.

Output format defaults to space seperated values but can also be output in Comma Seperated Values (CSV) or JSON formats. By default, the measurement unit is output but this can be disabled for feeding applications that can only handle numeric data.

By default, measurements are output in the same scale and resolution as displayed by the multimeter. When using autoranging, this can result in the measurement scale and resolution changing when the multimeter changes ranges. To avoid this, you can optionally lock the measurement scale. However, as the multimeter autoranges, it will change the resolution of the measurement value.

Interactive Mode

Specifying the -i option allows you to interactively control the multimeter remotely from the client. Using these controls, you can change the measurement range, switch between some functions, display min/max/relative/hold values, and turn the backligh on. The interactive controls correspond to the multimeter front panel buttons.

Offline Recording

The client can be used to initiate offline recording using the -R option. With this command, specify the measurement interval in seconds per measurement, and the number of measurements to record. The multimeter has the capacity to store up to 10,000 measurements.

Offline recorded measurements are downloaded using the -r option. Recorded measurements are replayed and output in the same way as realtime measurements. Timestamp, format and scale options can be used to control the measurement output.

Interfacing

The client is designed to inteface into other tools using the normal Unix pipe and redirection mechanisms.

Files

Measurement values can be written directly to file using redirects:

Write timestamped measurements in CSV format - owonb35 -c -d > measurements.txt

The tee command can be used to write measurement values to a file and also pipe them to another application.

owonb35 | tee measurements.txt | next_tool

gnuplot

gnuplot is a very flexible plotting program. The client can feed measurements to gnuplot in realtime using feedgnuplot.

owonb35 -s -x -b | feedgnuplot --domain --lines --stream --ymin 0 --ylabel 'Volts' --xlabel 'Seconds' --exit

It is best to lock the measurement unit and scale to prevent them jumping around if the multimeter autoranges during measurement. feedgnuplot doesn't handle non-numeric data in its input, so the output of measurement units need to be disabled. It also cannot handle measurements with less than one second resolution, which means that it can only display elapsed timestamps. Data written to file and loaded into gnuplot can display actual timestamps.

MQTT

MQTT is a publish/subscribe messaging system frequently used in Internet of Things networks. It allows clients to publish data onto a network for other clients to subscribe to. Data is usually published as single values or in JSON format.

Single value - omonb35 -x -b | mosquitto_pub -t voltage -l

JSON format - omonb35 -T -b -j | mosquitto_pub -t measurement -l

Protocol

The multimeter uses the Bluetooth Low Energy Generic Attributes (BLE GATT) to transmit measurements.

Realtime Measurements

Measurement data is output as a BLE notification with a 0xfff4 UUID. The packet consists of three uint16_t numbers.

The first number encodes the function, scale, and decimal places.

Overload                                1 1 1
Decimal--------------------------------------
                                          | |
DCmV         1 1 1 1 0 0 0 0  0 0 0 1 1 x x x  f0 18
DCV          1 1 1 1 0 0 0 0  0 0 1 0 0 x x x  f0 20
ACmV         1 1 1 1 0 0 0 0  0 1 0 1 1 x x x  f0 58
ACV          1 1 1 1 0 0 0 0  0 1 1 0 0 x x x  f0 60
                                             
DCuA         1 1 1 1 0 0 0 0  1 0 0 1 0 x x x  f0 90
DCmA         1 1 1 1 0 0 0 0  1 0 0 1 1 x x x  f0 98
DCA          1 1 1 1 0 0 0 0  1 0 1 0 0 x x x  f0 a0
                                            
ACuA         1 1 1 1 0 0 0 0  1 1 0 1 0 x x x  f0 d0
ACmA         1 1 1 1 0 0 0 0  1 1 0 1 1 x x x  f0 d8
ACA          1 1 1 1 0 0 0 0  1 1 1 0 0 x x x  f0 e0
                                            
Ohm          1 1 1 1 0 0 0 1  0 0 1 0 0 x x x  f1 20
kOhm         1 1 1 1 0 0 0 1  0 0 1 0 1 x x x  f1 28
MOhm         1 1 1 1 0 0 0 1  0 0 1 1 0 x x x  f1 30
                                            
nF           1 1 1 1 0 0 0 1  0 1 0 0 1 x x x  f1 48 
uF           1 1 1 1 0 0 0 1  0 1 0 1 0 x x x  f1 50
                                            
Hz           1 1 1 1 0 0 0 1  1 0 1 0 0 x x x  f1 a0
Duty         1 1 1 1 0 0 0 1  1 1 1 0 0 x x x  f1 e0
                                            
TempC        1 1 1 1 0 0 1 0  0 0 1 0 0 x x x  f2 20
TempF        1 1 1 1 0 0 1 0  0 1 1 0 0 x x x  f2 60
                                            
Diode        1 1 1 1 0 0 1 0  1 0 1 0 0 x x x  f2 a0
                                            
Continuity   1 1 1 1 0 0 1 0  1 1 1 0 0 x x x  f2 e0
                                            
hFE          1 1 1 1 0 0 1 1  0 0 1 0 0 x x x  f3 20
                                            
             +------+---+--------+-----+-----+
                F     0  Function Scale Decimal
                
                
Function
    0 0 0 0 - DCV
    0 0 0 1 - ACV
    0 0 1 0 - DCA
    0 0 1 1 - ACA
    0 1 0 0 - Ohm
    0 1 0 1 - Cap
    0 1 1 0 - Hz
    0 1 1 1 - Duty
    1 0 0 0 - TempC
    1 0 0 1 - TempF
    1 0 1 0 - Diode
    1 0 1 1 - Continuity
    1 1 0 0 - hFE

Scale
    0 0 1 - nano (n)
    0 1 0 - micro (u)
    0 1 1 - milli (m)
    1 0 0 - Unit
    1 0 1 - kilo (k)
    1 1 0 - mega (M)
    
Decimal Places
    0 0 0 - 0
    0 0 1 - 1
    0 1 0 - 2
    0 1 1 - 3
    1 0 0 - 4
    1 0 1 - 5
    1 1 1 - Overload

The second number bit encodes the reading type.

Hold-----------------------\   01/05 Autorange
Delta--------------------\ |   02/06 Autorange
Autorange--------------\ | |   04
Low Battery----------\ | | |
Min----------------\ | | | |   10
Max--------------\ | | | | |   20
                 | | | | | |
   00000000  X X X X X X X X
             8 4 2 1 8 4 2 1

The third number is the measurement digits as a signed magnitude binary number (msb is sign bit). It is converted to the floating point measurement value by using the number of decimal places as specified in the first number.

Interactive Commands

Interactive commands are sent by writing a uint16_t number to UUID 0xfff3.

0x0101 Select
0x0002 Auto
0x0102 Range
0x0003 Backlight
0x0103 Hold
0x0004 Bluetooth Off
0x0104 Relative
0x0105 Hz/Duty
0x0006 Normal
0x0106 Min/Max

Offline Recording

Starting

Offline recording is initiated by writing the current date and time, and then the measurement interval and count to UUID 0xfff1. Year of date is split into uint8_t numbers for century and decade/year.

Measurement interval and count are uint32_t numbers. The maximum number of measurements that can be recorded in 10,000.

2a:44:41:54:65:14:12:04:0e:11:07:1b:00:00:00:00
*  D  A  T  e [C][Y] [M][D][H][M][S]

2a:52:45:43:4f:72:64:2c:40:16:40:00:10:27:00:00
*  R  E  C  O  r  d  ,  [Sec/Rding] [Count    ]

Once recording has started, the multimeter will disconnect.

Downloading

The number of bytes of offline measurement record data available is obtained by the writing the following command and then reading the result from UUID 0xfff1.

2a:52:45:41:44:6c:65:6e:3f:00:00:00:00:00:00:00
*  R  E  A  D  l  e  n  ?

The result will be a buffer contain a uint32_t number of bytes available. This number represents the length of data plus a length counter. The number of measurements available is the (number of bytes/2) - 1.

The downloading of offline measurement data is trigger by writing the following command to UUID 0xfff1.

2a:52:45:41:44:31:3f:00:00:00:00:00:00:00:00:00
*  R  E  A  D  1  ?

The multimeter sends offline measurement record data using notifications with UUID 0xfff4. Data is sent in 20 byte packets. Int1 and Int3 correspond to the first and third numbers sent in the realtime measurement data above.

Start marker 
ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff

Header packet
14:12: 04:0e: 0e:17: 18:00: 02:00 :00:00 :2a:00: 00:00: 19:f0: 09:0e
[C][Y] [M][D] [H][M] [S]    [Interval  ]  [Byte count ] [Int1] [Int3]

Data packets
09:0e: 0a:0e: 0a:0e: 0a:0e: 0a:0e: 0b:0e: 0b:0e: 0b:0e: 0b:0e: 0b:0e
[Int3] [Int3] [Int3] [Int3] [Int3] [Int3] [Int3] [Int3] [Int3] [Int3] 

More data packets as required......

Finish Marker
ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff: ff:ff

Once the data is downloaded, the mutimeter returns to sending realtime measurement data.

owonb35's Issues

Compatibility with other chips?

many Aneng , UniT devices seems to use BT4LE device BK3432
Described here: https://mysku.me/blog/aliexpress/82493.html

Do you know/have a clue whatever this application may be able to pull data from those? (protocol may be different, but if it could just read the data stream... the rest could be done.)

Compilation error

Hello DeanCording,
I don't have that much experience compiling programs. When I call "make" I get this error message.

cc -Wall -O2 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include  owonb35.c  -o owonb35 -lgattlib -lglib-2.0 -lm
owonb35.c: In function ‘connect_device’:
owonb35.c:575:71: error: ‘BT_SEC_LOW’ undeclared (first use in this function); did you mean ‘BT_SECURITY’?
         connection = gattlib_connect(NULL, address, BDADDR_LE_PUBLIC, BT_SEC_LOW, 0, 0);
                                                                       ^~~~~~~~~~
                                                                       BT_SECURITY
owonb35.c:575:71: note: each undeclared identifier is reported only once for each function it appears in
owonb35.c:575:22: error: too many arguments to function ‘gattlib_connect’
         connection = gattlib_connect(NULL, address, BDADDR_LE_PUBLIC, BT_SEC_LOW, 0, 0);
                      ^~~~~~~~~~~~~~~
In file included from owonb35.c:38:0:
/usr/include/gattlib.h:276:20: note: declared here
 gatt_connection_t *gattlib_connect(const char *src, const char *dst, unsigned long options);
                    ^~~~~~~~~~~~~~~
owonb35.c: In function ‘main’:
owonb35.c:764:56: warning: passing argument 2 of ‘gattlib_adapter_scan_enable’ from incompatible pointer type [-Wincompatible-pointer-types]
             ret = gattlib_adapter_scan_enable(adapter, ble_discovered_device, BLE_SCAN_TIMEOUT);
                                                        ^~~~~~~~~~~~~~~~~~~~~
In file included from owonb35.c:38:0:
/usr/include/gattlib.h:214:5: note: expected ‘gattlib_discovered_device_t {aka void (*)(void *, const char *, const char *, void *)}’ but argument is of type ‘void (*)(const char *, const char *)’
 int gattlib_adapter_scan_enable(void* adapter, gattlib_discovered_device_t discovered_device_cb, int timeout, void *user_data);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
owonb35.c:764:19: error: too few arguments to function ‘gattlib_adapter_scan_enable’
             ret = gattlib_adapter_scan_enable(adapter, ble_discovered_device, BLE_SCAN_TIMEOUT);
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from owonb35.c:38:0:
/usr/include/gattlib.h:214:5: note: declared here
 int gattlib_adapter_scan_enable(void* adapter, gattlib_discovered_device_t discovered_device_cb, int timeout, void *user_data);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
owonb35.c:859:74: warning: passing argument 3 of ‘gattlib_read_char_by_uuid’ from incompatible pointer type [-Wincompatible-pointer-types]
             ret = gattlib_read_char_by_uuid(connection, &g_command_uuid, buffer, &len);
                                                                          ^~~~~~
In file included from owonb35.c:38:0:
/usr/include/gattlib.h:418:5: note: expected ‘void **’ but argument is of type ‘uint8_t * {aka unsigned char *}’
 int gattlib_read_char_by_uuid(gatt_connection_t* connection, uuid_t* uuid, void** buffer, size_t* buffer_len);
     ^~~~~~~~~~~~~~~~~~~~~~~~~
Makefile:16: recipe for target 'owonb35' failed
make: *** [owonb35] Error 1

Even if I use the pre-compiled version I get an error message.

error while loading shared libraries: libpython3.5m.so.1.0: cannot open shared object file: No such file or directory

I use Linux Mint 19 Tara and my last Python Version is 3.6.8 .
I hope you can help me.

With best regards
Sebastian

Is OWON USB Bluetooth adapter required?

Dear Dean,

Does this program require the (alledegly) custom USB Bluetooth 4.0 adapter ( https://eleshop.eu/owon-usb-bluetooth-dongle.html ) ?
If not, could you provide in the readme the USB chip you used on the computer?

I'd like to port this to BT41+ but I cannot get bluetooth connection working.

Thanks in advance.

Version of gattlib

Dear Mr. DeanCording,
I am sorry, I couldn't find your email using git.
So I am writing this issue with a hope for your help with compiling of owonb32 client under Xubuntu 18.04.03. It's not possible to compile the client. As I could see from the gcc log, the problem is in wrong version of gattlib I have in the system. There is no specific information about the version you used.
Would you be so kind to specify it?
I have compiled the library to work with Bluez 5.49.

The client compilation errors are likes this:
owonb35.c:575:71: note: each undeclared identifier is reported only once for each function it appears in owonb35.c:575:22: error: too many arguments to function ‘gattlib_connect’
connection = gattlib_connect(NULL, address, BDADDR_LE_PUBLIC, BT_SEC_LOW, 0, 0);
^~~~~~~~~~~~~~~
In file included from owonb35.c:38:0:
/usr/local/include/gattlib.h:276:20: note: declared here
gatt_connection_t *gattlib_connect(const char *src, const char *dst, unsigned long options);

Trouble connecting

I've been having a lot of trouble connecting to my meter, the automatic scan function doesn't work, and connecting through a MAC address works rarely, and even if I manage to connect, it spits out around 15 readings and then times out, after it times out I kill the meter, restart my bluetoothd service and try again, since the reconnection doesn't seem to work that well either, it's very finnicky in general.

I don't know if you have any interest in improving this program, but whether I fork your project or work on my own implementation, I am very thankful for the documentation that you've provided here.

If it's relevant:

• Owon B35T+ meter
• Ubuntu 20.04
• Bluez version 5.53