Advanced Features

High Frequency Streaming

Some developers may want to stream data from multiple motion sensors simultaneously or individually at frequencies higher than 100Hz. To accommodate this use case, acceleration, angular velocity, and magnetic field data have a packed output mode that combines 3 data samples into 1 ble packett increasing the data throughput by 3x.

mbl_mw_acc_set_odr(board, 200.0f);
mbl_mw_acc_set_range(board, 4.0f);

auto packed = mbl_mw_acc_get_packed_acceleration_data_signal(board);
mbl_mw_datasignal_subscribe(packed, nullptr, [](void* context, const MblMwData* data) {
    auto value = (MblMwCartesianFloat*) data->value;
    printf("{x: %.3f, y: %.3f, z: %.3f}\n", value->x, value->y, value->z);


In addition to using packed output, developers will also need to reduce the max connection interval to 7.5ms. Reducing the max connection interval can also be used to speed up log downloads.

mbl_mw_settings_set_connection_parameters(board, 7.5f, 7.5f, 0, 6000);


The internal state of the MblMwMetaWearBoard object can be converted into a byte array, which can then be saved to the disk. You will need to free the allocated memory after you are done using the byte array.

#include <iostream>
#include "metawear/platform/memory.h"

using std::ostream;

void serialize(ostream& os, MblMwMetaWearBoard* board) {
    uint32_t size;
    uint8_t* state = mbl_mw_metawearboard_serialize(board, &size);

    os.write((const char*) state, size);

To restore the board state, pass the byte array into mbl_mw_metawearboard_deserialize. You must still call mbl_mw_metawearboard_initialize after deserializing the state.

#include <vector>

using std::istream;
using std::vector;

void deserialize(istream& is, MblMwMetaWearBoard* board) {
    std::vector<uint8_t> state;
    while (is.good()) {
        char x;, 1);
    mbl_mw_metawearboard_deserialize(board,, state.size());

Anonymous Signals

Anonymous data signals are a variant of the Logger type used to retrieve logged data from a board that was not programmed by the current host device. Use mbl_mw_metawearboard_create_anonymous_datasignals to sync the host device with the board’s current logger state. If the function fails, a null pointer will be returned and the uint32_t parameter instead corresponds to a status code from the SDK.

Because of the anonymous nature of the object, users will need to rely on an identifier string to determine what kind of data is being passed to each route. Generate the identifier string by calling mbl_mw_logger_generate_identifier for each MblMwDataLogger type and match these values with mbl_mw_anonymous_datasignal_get_identifier.

#include "metawear/core/datasignal.h"
#include "metawear/core/logging.h"
#include "metawear/platform/memory.h"
#include "metawear/sensor/gyro_bmi160.h"

void identifier_demo(MblMwMetaWearBoard* board) {
    auto gyro = mbl_mw_gyro_bmi160_get_rotation_data_signal(board);
    auto gyro_y = mbl_mw_datasignal_get_component(gyro, MBL_MW_GYRO_ROTATION_Y_AXIS_INDEX);
    mbl_mw_datasignal_log(gyro_y, nullptr, [](void* context, MblMwDataLogger* logger) -> void {
        auto identifier = mbl_mw_logger_generate_identifier(logger);
        cout << "gyro_y identifier = " << identifier << endl;
#include "metawear/core/anonymous_datasignal.h"

// Use mbl_mw_metawearboard_create_anonymous_datasignals to retrieve log data from
// another device
void anonymous_signal_demo(MblMwMetaWearboard* board) {
    mbl_mw_metawearboard_create_anonymous_datasignals(board, nullptr, [](void* context, MblMwMetaWearBoard* board,
            MblMwAnonymousDataSignal** anonymous_signals, uint32_t size) {
        if (anonymous_signals == nullptr) {
            cerr << "Failed to create anonymous signals, status = " << (int32_t) size << endl;
        for (uint32_t i = 0; i < size; i++) {
            auto identifier = mbl_mw_anonymous_datasignal_get_identifier(anonymous_signals[i]);

            // identifier earlier extracted from calling
            // mbl_mw_logger_generate_identifier, use in if-else statements to identify
            // which anonymous signal represents gyro y-axis data
            if (!strcmp(identifier, "angular-velocity[1]")) {
                mbl_mw_anonymous_datasignal_subscribe(anonymous_signals[i], context, [](void* context, const MblMwData* data) {
                    printf("gyro y-axis: %.3f", *((float*) data->value));

As the C++ SDK does not yet support all available data sources, you will not be able to use this SDK to sync data from the accelerometer’s detection algorithms except the BMI160’s step and orientation detectors.