Extreme NXT: Extending the LEGO MINDSTORMS NXT to the Next Level
Extreme NXT: Extending the LEGO MIDSTORMS NXT to the Next Level is for intermediate-level users of NXT who would like to advance their capabilities by learning some of the basics of electronics. Plenty of examples are provided, and easy-to-follow instructions are included for building over 15 different sensors.
This makes a great reference for the NXT hardware interfaces. Examples even come complete with multiple, alternative NXT languages. The book is also abundant with illustrations.
NXT Motor Interfaces
Beyond NXT Motors
I2C Bus Communication
References Links and Sources
43V Powered Sensors
TwoWire Powered Sensors