MblMwMetaWearBoard

Like the MetaWearBoard (Android) and IMetaWearBoard (C#) classes, the MblMwMetaWearBoard struct is the C++ API’s representation of a MetaWear board and is the central type for using the API. The metawearboard.h header file provides functions for instantiating and retrieving information about a board.

Instantiation

Before you can instantiate a MblMwMetaWearBoard struct, you must first create a MblMwBtleConnection as outlined in the Bluetooth LE Communication section. Once you have your struct properly setup, call mbl_mw_metawearboard_create to instantiate a MblMwMetaWearBoard struct.

#include "metawear/core/connection.h"
#include "metawear/core/metawearboard.h"

int main(int argc, char **argv) {
    MblMwBtleConnection btle_conn = { nullptr, write_gatt_char, read_gatt_char, enable_char_notify };
    MblMwMetaWearBoard* board = mbl_mw_metawearboard_create(&btle_conn);
}

Initialize

After you have instantiated a MblMwMetaWearBoard, you then need to initialize its internal state by calling mbl_mw_metawearboard_initialize. Initializing can take a few seconds and will asynchronously alert the caller when it is finished. If initialization succeeded, MBL_MW_STATUS_OK will be passed to the callback function, otherwise a non-zero value will be returned instead signalling the task failed.

You can check if a ``MblMwMetaWearBoard``has been initialized by calling mbl_mw_metawearboard_is_initialized.

mbl_mw_metawearboard_initialize(board, nullptr, [](void* context, MblMwMetaWearBoard* board, int32_t status) -> void {
    if (!status) {
        printf("Error initializing board: %d\n", status);
    } else {
        printf("Board initialized\n");
    }
);

Initialization must be done everytime you connect to a board.

Device Information

Available device information characteristics are wrapped by the MblMwDeviceInformation struct and is accessed by calling mbl_mw_metawearboard_get_device_information. The function does allocate memory for the struct so you must free the memory when you are done with the struct.

auto dev_info = mbl_mw_metawearboard_get_device_information(board);
cout << "firmware = " << dev_info->firmware_revision << endl;
mbl_mw_memory_free((void*) dev_info);

Model

Despite the name, the MetaWearBoard interface communicates with all MetaSensor boards, not just MetaWear boards. Because of this, the header file provides the mbl_mw_metawearboard_get_model method that determines exactly which board the MblMwMetaWearBoard is currently communicating with.

cout << "model = " << mbl_mw_metawearboard_get_model(board) << endl;

Tear Down

Calling mbl_mw_metawearboard_tear_down will remove all data processors, loggers, timers, and recorded events from both the board and the struct’s internal state. It does not reset the board so any configuration changes will be preserved.

Modules

Modules are sensors or features supported by the MetaWear firmware. While the C++ API does not partition the module functions in the same way the Android and iOS APIs do, it does provide the mbl_mw_metawearboard_lookup_module function. The output is used to determine what kind of module is present, i.e. which accelerometer is on the board, or if the module is even supported on the board e.g. barometers are not available on all boards.

Constants identifying the modules are defined in the module.h header file.

Freeing Memory

When you are done using the struct, call mbl_mw_metawearboard_free. This function does not affect the state of the MetaWear board, it only frees the memory allocated by the mbl_mw_metawearboard_create function.