I have been using a simple Arduino sketch and a simple I2c.h TWI library to read to and write from both the MPU6050 and AK8975A devices with success. I also have successfully used Jeff Rowberg's I2cdev.h library to do the same with his MPU-9150 library hack. When I switched my own sketch to using Wire.h instead of I2c.h, I can still access the MPU6050 gyro and accelerometer data but can no longer read from or write data to the AK8975A, except I get a successful return of the initial read of the AK8975A's WHO_AM_I register. Any idea why Wire.h wouldn't work for the AK8975A while it works fine for the MPU6050 (gyro and accelerometer)? Thank you for your help.