Data Processor

Data processors are functions in the firmware that filter or transform sensor data and are represented by the MblMwDataProcessor struct.

In the C++ API, data processors can be thought of as a data signal whose data is produced by the on-board data processor. As such, a MblMwDataProcessor can be safely typecasted to a MblMwDataSignal.

Processor Id	Name	Functionality
0x01	Passthrough	Allow a specific # of data (samples) through
0x02	Accumulator	Running sum of data
0x02	Counter	Keeps a tally of how many times it is called
0x03	Averager / Low Pass Filter	Computes a running average of the data
0x03	High Pass Filter	Compute the difference of the current value from a running average of the previous N samples
0x06	Comparator	Removes data that do not satisfy the comparison operation
0x07	RMS	Computes the root mean square over multi component data
0x07	RSS	Computes the root sum square, or vector magnitude, over multi component data
0x08	Time	Only allows data to pass at fixed intervals
0x09	Math	Performs arithmetic or logical operations on the data
0x0a	Sample	Only allowing data through once it has collected a set number of samples
0x0b	Pulse	Detects and quantifies a pulse over a set of data
0x0c	Delta	Computes the dif between 2 successive data values and only allows data through that creates a diff > threshold
0x0d	Threshold	Only allows data through that crosses a boundary
0x0f	Buffer	Captures input data which can be read at a later time
0x10	Packer	Combines multiple data samples into 1 BLE packet
0x11	Accounter	Adds additional information to the BTLE packet
0x1b	Fuser	Combine data from multiple sources into 1

This section will focus on the MblMwDataProcessor struct. Details on supported processors and how to create them are covered in the Data Processor Types section.

ID

Data processors are identified by a unique numerical ID; as identified in the table above.

You can retrieve this id by calling mbl_mw_dataprocessor_get_id.

The data processor ID is used to lookup a previously created MblMwDataProcessor object with the mbl_mw_dataprocessor_lookup_id function.

The object is needed to remove/delete processors (see section below).

The object is useful as it can be used as the input to another processor. As such, it is possible to combine processors together for all sorts of functionality.

A high pass filter on the accelerometer data can remove noise which can then be set as the input to an RMM to combine the x,y,z axis data into a signal signal. This can further be set as the input to a comparator or threshold detector to determine if the accelerometer experienced a shock higher than 4Gs.

processor= self.libmetawear.mbl_mw_dataprocessor_lookup_id(self.board, 1)
self.libmetawear.mbl_mw_dataprocessor_remove(processor)

State

Some processors have an internal state that can be read and modified; the internal state is treated as a readable MblMwDataSignal.

In this example, a buffer process is used. The state of the buffer processor is the data in the buffer:

processor = libmetawear.mbl_mw_dataprocessor_lookup_id(board, id)
state_signal = libmetawear.mbl_mw_dataprocessor_get_state_data_signal(processor)
libmetawear.mbl_mw_datasignal_read(state_signal)

The state of the counter processor is the count itself.

# Previously setup the counter in function
processor = mbl_mw_dataprocessor_lookup_id(board, 2)
processor_state = mbl_mw_dataprocessor_get_state_data_signal(processor)
mbl_mw_datasignal_subscribe(processor_state, sensor_data_handler)

Removal

Removing a processor is handled by calling mbl_mw_dataprocessor_remove.

When a processor is removed, all processors that consume its output will also be removed.

processor= self.libmetawear.mbl_mw_dataprocessor_lookup_id(self.board, 1)
libmetawear.mbl_mw_dataprocessor_remove(processor)