Using the two hacked servos from the other day I decided to make them into a simple mobile platform. In addition I have a Wiimote nunchuck connected via the nunchucky from www.solarbotics.com. I am using the joystick to control the rotation of the two servos. The buttons and accelerometer data however are not used for anything so far with this experiment. I used some code that I found on the web that used the Arduino to decode the data from the nunchuck via the I2C connection and then send it to a terminal program using a serial interface. I then modified it to give abbreviated data data to the serial terminal, and also to drive the motors using PWM output from two of the Arduinos digital I/O pins.

So.... here is the code.... and yes... I know I need better comments....

/*

example code from www.windmeadow.com/node/42 modified to drive two continuous

rotation servos as PWM controlled gear motors.

uses the analog pins for nunchuck connection

analog 4= data

analog 5= clock

nunchuck uses 6 bytes for full set of data

0: x axis of analog stick left(min) 0x1e, center 0x7e, right 0xe1

1: y axis of analog stick down (min) 0x1d, center 0x7b, max 0xdf

2: x acceleration 1g (min) 0x48, medium 0x7d, max 0xb0

3: y acceleration 1g (min) 0x 46, medium 0x7a, max 0xaf

4: z acceleration 1g (min) 0x4a, medium 0x7e, max 0xb1

5: buttons/ alleleration LSB:

bit 0 z button (0= pressed)

bit 1 c button (0= pressed)

bit 2 and 3 x acceleration LSB

bit 4 and 5 y acceleration LSB

bit 6 and 7 z acceleration LSB

Scott Powers

6-10-2009

*/

#include Servo.h //stuff in italics needs to go in angle brackets

#include string.h

#include Wire.h

#undef int

#include stdio.h

Servo leftMotor;

Servo rightMotor;

uint8_t outbuf[6]; // array to store arduino output

int cnt = 0;

int ledPin = 13;

int delayTime = 50000;

void

setup ()

{

Serial.begin (19200);

Serial.print ("Finished setup\n");

Wire.begin (); // join i2c bus with address 0x52

leftMotor.attach(10);

rightMotor.attach(9);

nunchuck_init (); // send the initilization handshake

}

void

nunchuck_init ()

{

Wire.beginTransmission (0x52); // transmit to device 0x52

Wire.send (0x40); // sends memory address

Wire.send (0x00); // sends sent a zero.

Wire.endTransmission (); // stop transmitting

}

void

send_zero ()

{

Wire.beginTransmission (0x52); // transmit to device 0x52

Wire.send (0x00); // sends one byte

Wire.endTransmission (); // stop transmitting

}

void

loop ()

{

Wire.requestFrom (0x52, 6); // request data from nunchuck

while (Wire.available ())

{

outbuf[cnt] = nunchuk_decode_byte (Wire.receive ()); // receive byte as an integer

digitalWrite (ledPin, HIGH); // sets the LED on

cnt++;

}

// If we recieved the 6 bytes, then go print them

if (cnt >= 5)

{

move ();

}

cnt = 0;

send_zero (); // send the request for next bytes

delayMicroseconds(delayTime);

}

// Print the input data we have recieved

// accel data is 10 bits long

// so we read 8 bits, then we have to add

// on the last 2 bits. That is why I

// multiply them by 2 * 2

void

move ()

{

int joy_x_axis = map(outbuf[0],0x1E, 0xE1, 0, 180);

int joy_y_axis = map(outbuf[1],0x1d, 0xdf, 0, 180);

int turn= joy_x_axis-88;

int z_button = 0;

int c_button = 0;

int left=(joy_y_axis+turn);

int right=(180-joy_y_axis+turn);

rightMotor.write(right);

leftMotor.write(left);

// byte outbuf[5] contains bits for z and c buttons

// it also contains the least significant bits for the accelerometer data

// so we have to check each bit of byte outbuf[5]

if ((outbuf[5] >> 0) & 1)

{

z_button = 1;

}

if ((outbuf[5] >> 1) & 1)

{

c_button = 1;

}

Serial.print (joy_x_axis, DEC);

Serial.print ("\t");

Serial.print (joy_y_axis, DEC);

Serial.print ("\t");

digitalWrite(13, z_button);

Serial.print (z_button, DEC);

Serial.print ("\t");

Serial.print (c_button, DEC);

Serial.print ("\t");

Serial.print ("\r\n");

}

// Encode data to format that most wiimote drivers except

// only needed if you use one of the regular wiimote drivers

char

nunchuk_decode_byte (char x)

{

x = (x ^ 0x17) + 0x17;

return x;

}