dsquires

Are you using one of the example sketches for Rowberg's libraries?

You should connect the pressure sensor in parallel with the MPU6050 on the I2C bus. When the Arduino (or host) wants to talk to the MPU6050, it first sends the address (ID) of the MPU6050, 0x68 or 0x69. Then, the MPU6050 responds to any subsequent commands, and the MPL3115A2 knows that it needs to leave the bus idle. To talk to the MPL3115A2, the host sends the address(ID) of the MPL3115A2 (look at its datasheet) and the MPU6050 will not respond to any subsequent commands. Arduino MPU6050 |------| |------| | SCL|----x--------|SCL | | SDA|--x-|--------|SDA | |------| | | |------| | | | | MPL3115A2 | | |------| | |--------|SCL | |----------|SDA | |------| The external interface on the MPU6050 is so that the MPU can use the data from the external device (magnetometer) in the DMP calculations. If you want to get sensor data independently of the MPU, you should connect them as you would on any standard I2C bus.