Use your Raspberry Pi (or a Linux PC) to talk to a Lego NXT rover and then use a Wii remote to drive the rover.

Python Libraries

There are 2 sets of libraries that we used:

• nxt-python : to talk to the Lego Mindstorm NXT
• cwiid : to talk to Wii remotes

To install these libraries:

wget https://nxt-python.googlecode.com/files/nxt-python-2.2.2.tar.gz
tar -zxvf nxt-python-2.2.2.tar.gz
cd nxt*
sudo python setup.py install
sudo apt-get install python-cwiid

The Lego NXT brick needs to have Bluetooth turned on. Check the top left corner of the Brick’s screen to see if the Bluetooth symbol is showing. If it is not showing go into the Bluetooth options and turn it on.

The next step is to ensure that the Raspberry Pi can see the Lego NXT. The Pi can scan Bluetooth devices with the command:

hcitool scan

If the Bluetooth is working then you will see the Bluetooth address of the NXT., (for example: 00:16:53:04:23:3D). Using the NXT’s Bluetooth address you can pair the Pi and the Lego NXT by:

sudo bluez-simple-agent hci0 00:16:53:04:23:3D

For the pin code use the default of: 1234
The NXT will beep and prompt you for the pairing passkey.

After the Raspberry Pi is paired with the Lego NXT brick you are able to use Python to read the NXT sensors and control the motors. No NXT coding is required. In the Python NXT directory there are some examples, mary.py  is a good test example because it does not require any sensors or motors.

Our full Python code to control the NXT Rover with a Wii remote is below:

import cwiid
import time
import nxt.locator
from nxt.motor import *

print 'Looking for a Lego NXT ... may take up to 15 seconds...'
b = nxt.locator.find_one_brick()
print 'Lego NXT Connected'

left = Motor(b, PORT_B)
right = Motor(b, PORT_C)

print 'Press 1+2 on your Wiimote now...'
wii = cwiid.Wiimote()
time.sleep(1)
wii.rpt_mode = cwiid.RPT_BTN 
print 'WII Remote Connected'

while True:
 buttons = wii.state['buttons']
 if (buttons & cwiid.BTN_LEFT):
 right.brake()
 left.run(power = 100,regulated=False)
 time.sleep(0.1)

if (buttons & cwiid.BTN_RIGHT):
 left.brake()
 right.run(power = 100,regulated=False)
 time.sleep(0.1)

if (buttons & cwiid.BTN_UP):
 right.run(power = 100,regulated=False)
 left.run(power = 100,regulated=False)
 time.sleep(0.1)

if (buttons & cwiid.BTN_DOWN):
 left.brake()
 right.brake()
 time.sleep(0.1)