I2C

The I2C module allows you to directly communicate with a sensor via the I2C bus. I2C functions are defined in the i2c.h header file.

Data Signal

I2C data signals are retrieved by calling mbl_mw_i2c_get_data_signal. You will need to pass two parameters:

• Length variable that sets how many bytes the signal is expected to receive
• An unique ID identifying the signal

If the id value has already been used, the length parameter will be ignored and the previously created signal will be returned.

#include "metawear/sensor/i2c.h"

// create and get a datasignal for 1 byte of i2c data
auto i2c_signal= mbl_mw_i2c_get_data_signal(board, 1, 0xa);

Read

To read I2C data, use the mbl_mw_datasignal_read_with_parameters function with the parameters set by the MblMwI2cReadParameters struct.

#include "metawear/core/datasignal.h"
#include "metawear/sensor/i2c.h"

mbl_mw_datasignal_subscribe(i2c_signal, [](const MblMwData* data) -> void {
    printf("WHO_AM_I= %x", ((uint8_t*) data->value)[0]);
});

MblMwI2cReadParameters read_params= {0x1c, 0xd};
mbl_mw_datasignal_read_with_parameters(i2c_signal, &read_params);

Write

Writing data through the I2C bus is handled with the mbl_mw_i2c_write function.

#include "metawear/sensor/i2c.h"

void i2c_write(MblMwMetaWearBoard* board) {
    // Write to the ctrl_meas register on the RPro/CPro barometer
    uint8_t ctrl_meas= 0x37;
    mbl_mw_i2c_write(board, 0x77, 0xf4, &ctrl_meas, 1);
}