Didier Stevens

Here’s a small post with extra details on building an Ardubot; details I didn’t find online.

The missing info is which Arduino output lines control the 2 motors. Measuring with a multimeter reveals digital outputs 3, 5, 6 and 9.

I place and solder the motors like this:

The +-sign closest to the PCB:

Red wire soldered to + connector, black wire soldered to – connector:

I defined left motor and right motor like this:

And here’s the schema:

To power the left motor in a forward drive, set digital output 9 high and digital output 6 low.

To power the left motor in a reverse drive, do the oposite of a forward drive (9 low and 6 high).

To power down a motor, set both digital outputs low.

To power the right motor in a forward drive, set digital output 5 low and digital output 3 high.

To power the right motor in a reverse drive, do the oposite of a forward drive (5 high and 3 low).

Arduino code:

/*
	Ardubot motor-driving example program
	Version 0.0.1
	Source code put in public domain by Didier Stevens, no Copyright
	https://DidierStevens.com
	Use at your own risk

	History:
	2009/08/21: Start development
	2009/08/23: refactoring
*/

unsigned char PIN_HBRIDGE_1A = 9;
unsigned char PIN_HBRIDGE_2A = 6;
unsigned char PIN_HBRIDGE_3A = 5;
unsigned char PIN_HBRIDGE_4A = 3;

void MotorLeftStop()
{
  digitalWrite(PIN_HBRIDGE_1A, LOW);
  digitalWrite(PIN_HBRIDGE_2A, LOW);
}

void MotorLeftForward()
{
  digitalWrite(PIN_HBRIDGE_1A, HIGH);
  digitalWrite(PIN_HBRIDGE_2A, LOW);
}

void MotorLeftReverse()
{
  digitalWrite(PIN_HBRIDGE_1A, LOW);
  digitalWrite(PIN_HBRIDGE_2A, HIGH);
}

void MotorRightStop()
{
  digitalWrite(PIN_HBRIDGE_3A, LOW);
  digitalWrite(PIN_HBRIDGE_4A, LOW);
}

void MotorRightForward()
{
  digitalWrite(PIN_HBRIDGE_3A, LOW);
  digitalWrite(PIN_HBRIDGE_4A, HIGH);
}

void MotorRightReverse()
{
  digitalWrite(PIN_HBRIDGE_3A, HIGH);
  digitalWrite(PIN_HBRIDGE_4A, LOW);
}

void setup() {
  pinMode(PIN_HBRIDGE_1A, OUTPUT);
  pinMode(PIN_HBRIDGE_2A, OUTPUT);
  pinMode(PIN_HBRIDGE_3A, OUTPUT);
  pinMode(PIN_HBRIDGE_4A, OUTPUT);
}

void loop(){
  MotorLeftStop();
  MotorRightStop();
  delay(2000);

  MotorLeftForward();
  delay(2000);

  MotorLeftStop();
  delay(2000);

  MotorLeftReverse();
  delay(2000);

  MotorLeftStop();
  delay(2000);

  MotorRightForward();
  delay(2000);

  MotorRightStop();
  delay(2000);

  MotorRightReverse();
  delay(2000);

  MotorRightStop();
  delay(2000);

  delay(5000);
}

One tip: if you use the large wheels, get a header kit to raise the Arduino Duemilanove, otherwise the wheel will block access to the power and USB connectors:

Quickpost info

I couldn’t get my 2 Arduinos with an XBee shield to talk to each other, despite the instructions on the Arduino site.

The XBee shields I obtained use a XBee series 2 module, while the instructions on the Arduino site are for the older XBee module.

After configuring one of my XBee modules as coordinator, the XBee modules were able to communicate with each other.

You need the X-CTU configuration program to configure an XBee series 2 module as coordinator. To connect the XBee module to your PC, you’ve to:

1) remove the ATmega µp from the Arduino board (remember the orientation of the ATmega chip to put it back afterwards):

2: set the jumpers on the XBee shield to USB:

3) Connect the XBee shield to the Arduino, and then connect the Arduino via USB to your computer, run the X-CTU configuration program and read the configuration:

4) Select the coordinator function set and write it to the XBee module:

When the XBee module has restarted and if your other XBee module is powered on, you’ll see the LEDs of both modules starting to flash, indicating they formed a WPAN network.

After configuring the XBee module, revert to the original hardware configuration: disconnect the Arduino board from your PC, set the jumpers on the XBee shield back to XBee and reinsert your ATmega µp in the Arduino board (watch out for the polarity of the chip).

Now I’m able to run the simple example successfully.

Quickpost info