External
Interface
for the NXT
Robotic Brick
A stock NXT can get pretty
boring pretty quickly. Want to
soup up this Honda Civic and
turn it into a Lotus Esprit?
Well then keep reading!
by DENNIS BOGDEN
Additional sensors can be purchased for your NXT
including a compass, GPS, and temperature sensor.
However, if the application being designed is to use
a different type or brand of sensor or actuator, the NXT
interface is not readily apparent.
This article describes an interface using RobotC
software and integrated circuits with the Inter-IC Bus
(I2C) that enable you to interface your own sensors and
actuators to the NXT brick. Examples of device interfaces
are R/C servos, shape memory alloy wire, relays, stepper
motors, compasses and so on.
HARDWARE INTERFACE AND
SOFTWARE PROGRAM
I purchased some additional NXT interface cables from
LEGO and built breadboarded some circuits to make a
cable-breadboard adapter (Photo 1.) The pin numbers and
wire colors correspond to the following signals:
PHOTO 1
• Pin 1 (White) = Switch input
• Pin 2 (Black) = Switch ground [VSS]
• Pin 3 (Red) = Digital ground [VSS]
• Pin 4 (Green) = + 4 to 5 volts [VCC]
• Pin 5 (Yellow) = I2C SCL
• Pin 6 (Blue) = I2C SDA
60 SERVO 10.2008
