Wireless PC Controlled Robot Using Bluetooth

In the previous tutorial I have explained how to setup a basic serial connection between an Atmega16 controller Board and a computer/laptop. In this article we’ll learn how to control a robot using the computer/laptop wirelessly through Bluetooth.

Components Required

1. Atmega16 development board with 16MHz crystal

2. Serial Bluetooth Module(AUBTM/HC-05/HC-04/BLUSMIRF)

} 3. PC/Laptop running Windows XP/7/8

} 4. USB Bluetooth(Not required if you laptop/PC has inbuilt hardware)

} 5. Motor Driver L293D

} 6. 2 X 12V 100RPM Geared DC motors

7. 2 X Wheels

8. Chassis

9. Castor wheel

10. Female jumper wires

Software Required

Serial Port Software on your PC (RealTerm/HyperTerminal/TeraTerm/Putty/ Your own Program)

Block-Diagram

Mechanical Construction:

Let us start with the hardware assembly part first. It should be simple since we are using a ready-made chassis. Start by attaching the motors and castor wheel to the chassis.

Next attach the wheels to the motor shafts using the screw provided on the wheel.

Connect the wires emerging from the two motors to the output pins of the L293D motor driver.

After all connections are made, this is how it looks.

Remember: RX (PIN 14) of controller to TX of modem and TX (PIN 15) of controller to RX of modem.

Code and Set up Instruction

Code Explanation:

Let us start from the main function.

·Lower nibble of PORT A connected to motor driver are configured as outputs.

·USART of the microcontroller is initialized using the BlueInit() function which sets the baud rate, configures the character sizes and enables the transmission and reception.

·Enter into an infinite while loop.

· Read a byte from the RX line using the “BlueRdChar()” function(waits for a data to be available at the RX pin of the controller, reads it when available and then returns the data which was read to the main function. Note that it is of “unsigned integer” type so it returns an ASCII code value of the character sent) and store it in a variable named “value” which is of type “unsigned char”.

· Write the same data which was stored in the variable “value” into the UDR and send it to the PC through the TX line of the microcontroller using “BlueWrChar(unsigned char d)” function (which waits until the UDR is ready and when it is, it loads the UDR with the data stored in the variable “d” and then the data is sent to the PC through the TX pin of the controller.)

· Check the character present in the variable “value”

If it contains ‘w’ or ‘W’, set the output port such that both motors move forward.

If it contains ‘s’ or ‘S’ , set the output port such that both motors move backward.

If it contains ‘d’ or ‘D’ , set the output port such that left motor moves forward and right motor remains at rest.

If it contains ‘a’ or ‘A’, set the output port such that right motor moves forward and left motor remains at rest.

If it contains a <space> then set the output port such that both the motors stop.

Setup Instructions:

1. You can either compile the code given using a suitable compiler like WINAVR with ATMEL STUDIO/AVR STUDIO or simply burn the “demo.hex” file give below. Before burning the hex file into you microcontroller, remember to change you Fuse bit Settings in order to make your microcontroller run at 16MHz using external crystal.

High fuse=0xC9

Low fuse=0xFF

(Warning: Be very careful while programming the fuse bits. If you set it with wrong values then the microcontroller may be permanently disabled.)

2. Turn on the Bluetooth on your computer and also the circuit setup. Wait for few seconds to let the computer connect to your Development board’s Bluetooth device (Refer the previous tutorial if you are establishing a connection for the first time.)

3. Open the serial communication software in your PC/Laptop i.e. RealTerm/HyperTerminal.

Note: I’m using my own software.

4. If you are using RealTerm then go to the Port Tab and set it as follows.

Baud: 9600

Port: <The port where the Serial Bluetooth Modem is virtually connected to>

Data bits: 8

Parity: None

Stop bits: 1

Hardware Flow Control: None

5. Now try to send some characters. If you have done everything correctly then you should see the following happening:

Character Sent	Robot’s Motion	Message on the REALTERM Display
‘W’ or ‘w’	Forward	ROBOT MOVING FORWARD
‘D’ or ‘d’	Right turn	ROBOT MOVING RIGHT
‘S’ or ‘s’	Reverse	ROBOT MOVING REVERSE
‘A’ or ‘a’	Left turn	ROBOT MOVING LEFT
<spacebar>	Stop	ROBOT HAS STOPPED
Any other key	No change	COMMAND NOT FOUND

Note: If there is an error in the Robot’s motion, i.e. say the robot moves in reverse direction when we press ‘w’ key instead of moving forward then don’t worry. It’s just because of the wrong connections between the motor driver and Development Board. Just inter change those connections and check again.

Project Source Code

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/*
 * BluePCRobo.c
 *
 * Created: 7/2/2013 6:02:08 AM
 * Author: GANESH SELVARAJ
 */ 
 
 
 
 
#define F_CPU 16000000UL
 
#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)
 
#include<avr/io.h>
#include<util/delay.h>
 
 
void BlueInit()
{
UCSRB |= (1 << RXEN) | (1 << TXEN);   // Enable transmission and reception
 
UCSRC |= (1 << URSEL) | (1<<USBS) | (1 << UCSZ0) | (1 << UCSZ1);
// Use 8-bit character sizes
 
UBRRL = BAUD_PRESCALE;
 
UBRRH = (BAUD_PRESCALE >> 8);
 
}
 
void BlueWrChar(unsigned char d)
{
while ((UCSRA & (1 << UDRE)) == 0); // wait till UDR is ready
 
UDR = d; // send data
}
 
unsigned int BlueRdChar()
{
while ((UCSRA & (1 << RXC)) == 0); // wait until data has been received
 
return(UDR); // return the byte
}
 
void BlueWrString(const char *msg)
{
 
 BlueWrChar('r');
 BlueWrChar('n');
 while(*msg!='')
 {
BlueWrChar(*msg);
msg++;
 }
 BlueWrChar('r');
 BlueWrChar('n');
}
 
 
 
int main()
{
unsigned char value;
 
DDRA=0x0F; 
 
_delay_ms(50); // delay of 50 mili seconds
BlueInit(); // initialization of USART
while(1)
{
value=BlueRdChar(); // get data from serial port
 
BlueWrChar(value); // send the same data back to the PC
if (value=='w' || value=='W')
{
PORTA=0x09;
BlueWrString("ROBOT MOVING FORWARD");
}
else if (value=='s' || value=='S')
{
PORTA=0x06;
BlueWrString("ROBOT MOVING REVERSE");
}
else if (value=='d' || value=='D')
{
PORTA=0x01;
BlueWrString("ROBOT MOVING RIGHT");
}
else if (value=='a' || value=='A')
{
PORTA=0x08;
BlueWrString("ROBOT MOVING LEFT");
}
else if (value==' ')
{
PORTA=0x00;
BlueWrString("ROBOT HAS STOPPED");
}
else
{
BlueWrString("COMMAND NOT FOUND");
}
 
}
return 0;
}
 
 
 
 
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