programming your ibot
TRANSCRIPT
TAG ROBOTICS
www.tagonnet.com
Programming your iBot
1. Program to blink an LED Since this is our first program, we will try to keep things simple. The following program will
blink an
LED on the board at a particular rate.
A generic algorithm for such a program will be something like this:
Step 1: Turn ON the LED
Step 2: Wait for sometime
Step 3: Turn OFF the LED
Step 4: Wait for sometime
Step 5: Goto Step1
To turn ON an LED on the iBOT board, we need to send logic 0 to that particular pin (since
LEDs are
connected in the active low configuration).
In order to introduce a delay, we need to eat up some processor time. The simplest way to achieve
this
is to perform a NOP (No Operation) multiple times. And continuous looping can be achieved by
either using the statement “goto” or more appropriately by using the while() loop.
Now let’s see how we can put all of these things together in a C program. // Program to blink an LED // #include<REG52MOD.h> //we include the necessary header file here void delay(unsigned int delay) //This a simple delay function using the //nested ‘for loop’ { unsigned int i,j; for(i=0;i<=1000;i++) for(j=0;j<=delay;j++); } void main(void) //main program begins here { while (1) //since there is no where to return //we put it in an infinite loop { RXD=0; //LED 1 is on pin RXD at PORT 3_1, we //turn it ON delay (20); //wait for a short time RXD=1; //turn the LED 1 OFF delay(20); //wait for a short time } }
We begin with including the header file for the microcontroller. Next we write the delay()
function
using the nested for loop. Don’t worry about the exact time of delay over here, you can
experiment
with different values and see what difference it makes. For example, replacing delay(20) with
delay(60) will reduce the frequency while delay(10) would increase the frequency. You could
also try
and use all the LEDs and generate different patterns.
Note: The LEDs are connected in an active-low configuration. Therefore, to turn ON an LED, we
TAG ROBOTICS
www.tagonnet.com
need to send logic 0 and not logic 1.
2. Program using Switches and LEDs Now that we know how to turn on/off a particular pin of the microcontroller, as seen in the
previous
example, let’s see how we can take inputs from a particular pin and execute actions based on its
state.
In this example, we will be using switches as our inputs and LEDs as the outputs. The simplest
way to
know the state (is it high or low?) of a particular pin is to poll it continuously.
The algorithm would go something like this:
Step 1: Check if Switch 1 is pressed; if pressed, turn ON LED 1, else, turn it OFF.
Step 2: Check if Switch 2 is pressed; if pressed, turn ON LED 2, else, turn it OFF.
.
.
.
Step n: goto step 1.
Lets see how a C program based on this algorithm would look like: // Program using Switches and LEDs // #include<REG52MOD.h> //we include the necessary header file here void main(void) //main program begins here { P3=0x3C; //initialize PORT 3 to 00111100 = 0x3C while (1) //since there is no where to return, //we put it in an infinite loop { if (P3_2==0) //check if Switch 1 is pressed { P3_0=0; //if pressed, turn ON LED 1 } else P3_0=1; //else turn it OFF if (P3_3==0) //check if Switch 2 is pressed { P3_1=0; //if pressed, turn ON LED 2 } else P3_1=1; //else turn it OFF if (P3_4==0) //check if Switch 3 is pressed { P3_6=0; //if pressed, turn ON LED 3 } else P3_6=1; //else turn it OFF if (P3_5==0) //check if Switch 4 is pressed { P3_7=0; //if pressed, turn ON LED 4 } else P3_7=1; //else turn it OFF } }
You will notice that we have written P3=0x3C at the very beginning of our program. This is done
to
set PORT 3’s pin 2, 3, 4 and 5 as inputs since we have connected our switches to them while pin
0, 1,
6 and 7 are the outputs where LEDs are connected. (1 � Input, 0 � Output)
TAG ROBOTICS
www.tagonnet.com
Note: The switches are connected in an active-low configuration. Therefore, whenever a switch is
pressed, we will receive logic 0 on that particular pin and not logic 1.
3. Program using a Sensor and a DC Motor Let’s try and make our next program more animated. In this example, we will control the
direction of
the motor based on the state of a sensor.
Here’s the algorithm:
Step 1: Initialize the ports
Step 2: Check the state of the sensor; if active, turn motor in one direction, else, turn it in other
direction.
Step 3: goto step 2
One IR proximity sensor is connected to PORT 1’s pin 0 and one motor is connected to M1 (pin 0
and
1 of PORT 2) // Program using Sensor and DC Motor // #include<REG52MOD.h> //we include the necessary header file here void main(void) //main program begins here { P1=0xff; //initialize PORT 1 as input P2=0x00; //initialize PORT 2 as output while (1) //since there is no where to return, //we put it in an infinite loop { if (P1_0==0) //check if sensor at PORT1.0 is active { //0 active, 1 inactive P2=0x01; //if active, turn motor in one //direction (0000 0001) } else P2=0x02; //else turn it in other direction (0000 0010) } } Similarly, you can write a code to turn both the motors and use both sensors together.
4. Program using the LCD module LCD is one of the most multipurpose module a robot can have. It can be used to display
information,
check various states of the robot, see the parameters as you feed them and also as a handy
debugging
tool. And the ‘cool’ factor cannot be understated aswell. iBOT uses a 2x16 backlight display that
is
compatible with the universally accepted Hitachi format. LCDs are not as easy to use as the LEDs
but
they are not very difficult either.
To make things simpler for you, we have written a small library for all the LCD functions. All
you
need to do is to add the LCD.h and delay.h header files in the C:\Keil\C51\INC folder before you
use
it.
TAG ROBOTICS
www.tagonnet.com
Let’s look at the LCD functions that we have at our disposal:
• LCD_INIT()
Initializes the LCD in 2 line 4 bit mode with blinking cursor.
• LCD_WRITE(‘T’)
Used to write any character T to the LCD.
• LCD_STRING(“Xplore Robotics”)
Used to write a string on the LCD (max 16 characters in length)
• LCD_CMD(X)
To give commands to the LCD. X can be as follows
PUTLINE1 – Places cursor on line1
PUTLINE2 - Places cursor on line2
To place the cursor on a particular character box it is addressed as follows:
Command = LCD_CMD(0b1XXX XXXX);
where xxx xxxx is the address of character in binary.
Note: LCD row 1 address starts at 0x00 and row 2 starts at 0x40 but with the MSB set, the
addresses
are 0x80 and 0xC0 respectively.
Eg: To put cursor on 3 character line 1
LCD_CMD(0x83);
To put cursor on 5 character line 2
LCD_CMD(0xC5);
• LCD_CLEAR()
Clears LCD screen.
Here’s a sample program for using the LCD module with the help of the above functions: // Program using the LCD module// #include<REG52MOD.h> //Include the necessary header files #include<delay.h> #include<LCD.h> void main (void) { LCD_INIT(); //Initialize the LCD module LCD_STRING("TRI"); //Send a string to display LCD_CMD(PUTLINE2); //Move the cursor to second line LCD_STRING("HELLO WORLD !!"); //Send a string to display while(1){} //Loop Infinitely }
5. Program to communicate with the PC via
UART In this section we will learn how to make your iBOT communicate with the PC through the
UART
channel. In order to do this, first refer to the datasheet of 89V51RD2 microcontroller and have a
look
at the UART section and the SCON (serial port control) register configurations.
In the following program, the microcontroller will send a “start” string to the PC at the beginning
of
the execution and simultaneously accept data coming from the PC (anything that you type on the
keyboard) and display in on to the onboard LCD module. //Program using to communicate with the PC via UART// #include<REG52MOD.h> #include<delay.h>
TAG ROBOTICS
www.tagonnet.com
#include<LCD.h> unsigned char RXED,TXED; void UART_INIT(void) //UART Initialization { SBUF=0x00; //Empty Serial Buffer SM0=0; //Set UART SM1=1; //in mode 1 SM2=0; REN=1; //Receive Enable TMOD=0x2F; //Set baud TH1=253; //rate as 9600bps TR1=1; ES=1; //Enable serial interrupts EA=1; //Global interrupt enable } void TX(unsigned char dat) //Transmit Data { SBUF=dat; delay(10); } void RXTX_int(void) interrupt 4 //Serial interrupt ISR { if(RI==1) { RI=0; //Reset receive data bit RXED=SBUF; LCD_WRITE(RXED); //Display received character on LCD } if(TI==1) { TI=0; //Reset transmit data bit } } void main(void) //Main program begins here { LCD_INIT(); //Initialize LCD UART_INIT(); //Initialize UART delay(1); //wait for a while
TX('S'); //Transmit S TX('t'); //Transmit t TX('a'); //Transmit a TX('r'); //Transmit r TX('t'); //Transmit t while(1){} }
After loading the program on to your iBOT controller, open the Hyper Terminal on your PC.
You can find it in Start > Programs > Accessories > Communications > Hyper Terminal Step 1: Enter a name for the connection
Step 2: Select the COM port and configure its properties
6. Line Following Robot Time to actually build a robot! Let’s put everything that we learned till now in our next program.
Line
following is one of the simplest task a robot can perform. There are many algorithms and sensor
TAG ROBOTICS
www.tagonnet.com
configurations designed to do this.
Here’s one of the simplest and fail safe line follower’s algorithm:
In this configuration we use two line sensors.
YES
YES
YES
NO
YES
NO
NO
NO
START
Initialize
Ports
Is left line
sensor
active?
Is right line
sensor
active?
Turn right
Turn Left
Is left line
sensor
active?
Go straight
Is right line
sensor
active?
Basically, the robot will always try to get the sensors on the line alternately, thus moving in a
‘zigzag’
path and eventually follow the line. The following code is written to follow a ‘black’ line on a
‘white’ surface but it can be easily modified to follow a ‘white’ line on a black surface. // LINE FOLLOWING ROBOT // //Right line sensor connected to PORT1.0 //Left line sensor connected to PORT1.1 //Right motor connected at M2 //Left motor connected at M1 #include<REG52MOD.h> //we include the necessary header file here #define forward 0x05; // 0000 01 01 #define right 0x01; // 0000 00 01 #define left 0x04; // 0000 01 00 #define linesensor_right P1_0 #define linesensor_left P1_1 void main(void) //main program begins here { P1=0xff; //initialize PORT 1 as input (sensors) P2=0x00; //initialize PORT 2 as output (motors) while (1) //since there is no where to return,
TAG ROBOTICS
www.tagonnet.com
//we put it in an infinite loop { if (linesensor_right==0) //check if right sensor has detected // a line (black surface) { while(linesensor_left==1) //if detected, then turn right till { //the left sensor comes on the line P2=right; } } if (linesensor_left==0) // check if left sensor has detected // a line { while(linesensor_right==1) //if detected, then turn left till
11 { //the right sensor comes on the line P2=left; } } else { P2=forward; //else go forward } } }
7. Obstacle Avoiding robot Obstacle avoiding behavior is a prerequisite in any mobile robotic application. In this project we
will
learn to add such a behavior in our iBOT.
Here’s a simple algorithm:
Step 1: check if right ir proximity sensor is active; if active, turn left for a while
Step 2: check if left ir proximity sensor is active; if active, turn right for a while
Step 3: else move forward
Step 4: goto step 1 // OBSTACLE AVOIDING ROBOT // //Right proximity sensor connected to PORT1.2 //Left proximity sensor connected to PORT1.3 //Right motor connected at M2 //Left motor connected at M1 #include<REG52MOD.h> //we include the necessary header file here #include<delay.h> #define forward 0x05; // 0000 01 01 #define turnleft 0x06; // 0000 01 10 left motor = backwards, // right motor = forward #define turnright 0x09; // 0000 10 01 left motor = forward, // right motor = backwards #define obst_right P1_2 #define obst_left P1_3 void main(void) //main program begins here { P1=0xff; //initialize PORT 1 as input (sensors) P2=0x00; //initialize PORT 2 as output (motors)
TAG ROBOTICS
www.tagonnet.com
while (1) //since there is no where to return, //we put it in an infinite loop { if (obst_right==0) //check if right sensor has detected an obstacle { P2=turnleft; //if detected, turn left for some time delay(30); } if (obst_left==0) //check if left sensor has detected an obstacle { P2=turnright; //if detected, turn right for some time delay(30); } else { P2=forward; //else go forward } } }
By changing the delay variable we can make the robot turn for some specific degrees after it
detects
an obstacle. But the turns will not be precise since they will change as the battery drains.
Note: In this particular case, the turning would be ‘in place’ i.e., while turning, both the motors
will
run in opposite direction unlike the line follower, where the turns were turning by ‘stopping’
either of
the motor.
8. Sumo Robot In the previous two examples we learned how to
use the line sensing modules as well as the IR
proximity modules. Now let’s see how we can
have a behavior that uses both of these sensors
together. A sumo robot fits this bill perfectly.
Inspired from the tradition ‘human’ sumo
competitions held in Japan, robotics enthusiasts
soon started having robotics sumo. Sumo
robotics competitions are now held around the
world under various weight and size ‘classes’
just like the real ones.
In a typical sumo robotics competition, two
robots compete against each other inside a sumo
ring. The ring is a made up of a black surface
with a white line around its circumference as
shown. The idea is to push the opponent out of
the ring in the stipulated time frame.
A typical sumo robot flowchart: NO
Start
Initialize ports
Is the opponent
TAG ROBOTICS
www.tagonnet.com
on the left and
me not on the
edge?
Is the right
line sensor
active?
Is the opponent
on the right and
me on the edge?
Is the opponent
in front and me
not on the edge?
Is the right
line sensor
active?
Turn left
Turn right
Go forward
Turn backwards
then turn left
Turn backwards
then turn right
Go forward
NO
NO
NO
NO
YES
YES
YES
YES
16 // SUMO ROBOT // //Right line sensor connected to PORT1.0 //Left line sensor connected to PORT1.1 //Right proximity sensor connected to PORT1.2 //Left proximity sensor connected to PORT1.3 //Right motor connected at M2 //Left motor connected at M1 #include<REG52MOD.h> //we include the necessary header file here #include<delay.h> #define forward 0x05 // 0000 01 01 #define reverse 0x0A // 0000 10 10 #define turnleft 0x06 // 0000 01 10 left motor = backwards, // right motor = forward #define turnright 0x09 // 0000 10 01 left motor = forward, // right motor = backwards #define linesensor_right P1_0 #define linesensor_left P1_1 #define obst_right P1_2 #define obst_left P1_3 void main(void) //main program begins here { P1=0xff; //initialize PORT 1 as input (sensors) P2=0x00; //initialize PORT 2 as output (motors) while (1) //since there is no where to return,
TAG ROBOTICS
www.tagonnet.com
//we put it in an infinite loop { while ( obst_right==0 //check if right sensor has && obst_left==1 //detected the opponent && linesensor_right==1 //and make sure that the robot is && linesensor_left==1) //not on the edge { P2=turnright; //if detected, turn right } //(i.e., towards the opponent) while ( obst_left==0 //check if left sensor has && obst_right==1 //detected the opponent && linesensor_right==1 //and make sure that the robot is && linesensor_left==1) //not on the edge { P2=turnleft; //if detected, turn left } //(i.e., towards the opponent) while ( obst_left==0 //check if both sensors && obst_right==0 //have detected the opponent && linesensor_right==1 && linesensor_left==1) { P2=forward; //if detected, go forward } //chase him and push him
17 if (linesensor_right==0 ) //check if right line sensor has // detected the ring { P2=reverse; //if detected, go reverse for a while delay(40); P2=turnleft; //then turn left for a while delay(30); P2=forward; //and go forward } if (linesensor_left==0 ) //check if left line sensor has //detected the ring { P2=reverse; //if detected, go reverse for a while delay(40); P2=turnright; //then turn right for a while delay(30); P2=forward; //and go forward } else { P2=forward; //else go forward } } }