Sliding-Window-Average

MetaBase configures MetaSensor boards to stream data to your MetaHub. It saves all data to CSV files and can also sync the data to the MetaCloud service.

Config File

The primary way to configure the application is with a JSON config file which is passed to the app via the --config options. Your config file must have at minimum the devices and sensors defined.

sudo npm start -- --config metabase-config.json

Commands

The first config option to set is the command key which controls what the app will do. You can choose from the following actions:

Action	Description
stream	Stream data realtime to the host device, also graphs the data live
log	Records data to the on-board flash memory, can download later with any MetaBase app
download	Retrieves the data from any board setup to record data with a MetaBase app

{
  "command": "stream"
}

Devices

The devices key is an array that holds the mac addresses of the devices to use. The array elements can either be a MAC address string or an object containing both the MAC address string and a user defined name identifying the device.

{
  "devices": [        
    "D4:5E:82:E1:15:01",
    {"mac": "D5:7B:B9:7D:CE:0E", "name": "Demo Unit"}
  ]
}

In the above example, the D4:5E:82:E1:15:01 mac address will have a default name assigned to it whereas the D5:7B:B9:7D:CE:0E will be referred to as "Demo Unit" in both
the UI window and MetaCloud

Sensors

The sensors key is an object that the app uses the configure and enable the various on-board sensors. Its keys are the names of the enabled sensors and the values contain the sensor configuration.

Each sensors have their own configurable parameters, detailed in the below table:

Name	Parameters	Example
Accelerometer	odr, range	{ "odr" : 100.0, "range": 2.0 }
Gyroscope	odr, range	{ "odr" : 25.0, "range": 250.0 }
Magnetometer	odr	{ "odr" : 25.0 }
Quaternion	accRange, gyroRange	{ "accRange": 2.0, "gyroRange": 250.0 }
Euler Angles	accRange, gyroRange	{ "accRange": 4.0, "gyroRange": 500.0 }
Linear Acceleration	accRange, gyroRange	{ "accRange": 8.0, "gyroRange": 1000.0 }
Gravity	accRange, gyroRange	{ "accRange": 16.0, "gyroRange": 2000.0 }
Ambient Light	odr, gain	{ "odr": 10.0, gain: 4 }
Pressure	odr	{ "odr": 1.96 }
Temperature	period	{ "period": 1800 }
Humidity	period	{ "period": 3600 }

For example, to sample accelerometer (+/-4g @ 100Hz), gyro (+/-1000 deg/s @ 100Hz), and mag data (25Hz):

{
    "sensors": {
        "Accelerometer": {"odr" : 100.0, "range": 4.0},
        "Gyroscope": {"odr" : 100.0, "range": 1000.0},
        "Magnetometer": {"odr" : 25.0}
    }
}

For all sensors, the odr or period parameter must be set if applicable. The app will select default values for the other parameters if not set by the user, and in the case where invalid values are selected, the closest valid value will be used instead.

Units

Sampling frequency values are expressed in Hz except for temperature and humidity which express them in seconds. For example, the previous JSON snippet will set the sensors to sample at 100.0Hz, 100.0Hz, and 25.0Hz respectively. However, the below JSON snippet will sample temperature and humidity at 30min and 1hr respectively (1800s / 3600s):

{
    "sensors": {
        "Temperature": {"period" : 1800.0 },
        "Humidity": {"period" : 3600.0 }
    }
}

Note that the period key is used in lieu of odr.

MetaCloud Syncing

As mentioned in the opening paragraph, this app can also sync to the MetaCloud service. To enable cloud sync, add the cloudLogin key along with your MetaCloud login credentials. The credentials are expressed as a JSON object with username and password keys.

{
    "cloudLogin": {
        "username": "foo",
        "password": "bar"
    }
}

Resolution

The resolution key is optional and sets the windows' width and height for the real time graphs. If not set, the application will automatically create windows 1/4th the screen resolution.

{
    "resolution": {
        "width": 960,
        "height": 540
    }
}

Command Line Options

All settings in the config file have equivalent command line options. The --devices and --sensors flags are require and can be repeated for multiple devices and sensors respectively.
All other flags are optional.

The table below maps JSON keys to their matching option:

JSON Key	Command Line	Required
command	--command	N
devices	--device	Y
sensors	--sensor	Y
resolution	--width, --height	N
cloudLogin	--cloud-user, --cloud-passwd	N

The JSON configuration from the previous section can equivalently expressed in the command line as follows:

sudo npm start -- --device D4:5E:82:E1:15:01 --device "D5:7B:B9:7D:CE:0E=Demo Unit" \
    --sensor Accelerometer='{"odr" : 100.0, "range": 4.0}' \
    --sensor Gyroscope='{"odr" : 100.0, "range": 1000.0}' \
    --sensor Magnetometer='{"odr" : 25.0}' \
    --width 960 --height 540 \
    --cloud-user foo --cloud-passwd bar \
    --command stream

Disable RealTime Graph

By default, the app will create a window for each connected board and graph the data in real time, one graph per stream. The realtime graphs can consume a lot of resources so users can disable it by passing in the --no-graph option in the command line.

sudo npm start -- --config metabase-config.json --no--graph

This graph is only available when streaming the data.