An Embedded system blog

Triangular wave generator in c

2013-01-11T10:16:00.001-08:00

Here is the code to generate a triangular wave of 8 bit resolution

1:  void main()  
2:  {  
3:  unsigned char i;  
4:  while(1)  
5:  {       
6:       for(i=0;i<0xff;i++)  
7:            { /* Generate rising edge */  
8:            delay_ us(1);  
9:            PORTB= i; //data output to port B  
10:            }  
11:       for(i=0xfe;i>0x00;i--)   
12:            {/* Generate falling edge */  
13:            delay_ us(1);  
14:            PORTB = i; //data output to port B  
15:            }  
16:  }  
17:  }

You can directly give the output to any port in which DAC is connected or you can use it for internal reference also.
This can be used to generate triangular wave in any microcontroller like AVR, 8051, PIC, ARM.
And triangular waves are also essential in doing modulation.

Ramp wave generator in c

2013-01-11T09:37:00.000-08:00

Here is a simple ramp wave generator you can directly give data to DAC or use it for your internal reference...

1:  //Ramp wave generating in c   
2:  Void main()  
3:  {  
4:       Int I;  
5:       I=0;  
6:       While(1)  
7:       {  
8:            I++;  
9:            delay_ms(1)//this count decides the frequency   
10:            if(I>=256) // this count decides the amplitude  
11:            {  
12:                 I=0;  
13:            }  
14:       }  
15:  }

Password protect your microcontroller

2011-10-23T07:59:00.001-07:00

Untitled Document

Hello friends, a good idea of privileging the execution of main program of microcontroller came in my mind after watching a Si-Fi movie……and I did it………

Password protecting your microcontroller is one of the coolest things you can do with it……

I created a routine that reads 5 keystrokes and then checks weather the inserted password is right or not.

the micro controller here used is Atmega 8535

Not discussing much more about logic, here is the program

----------------------------------------------------------------------------------------------

void main()

{

unsigned char a,b,c,d,e;

DDRA=0x00;

PORTA=0xff;

//ask for password

while(1)

{

lcd_init();

lcd_string("Enter a 5 digit");

lcd_gotoxy(1,0);

lcd_string("Password:");

//read password

while(PINA==0xff); //if all keys open stay here

a=PINA;

delayms(200);

lcd_gotoxy(1,0);

lcd_string("Password:*");

while((PINA&0xf0)!=0xf0); //wait to release the key

while(PINA==0xff);

b=PINA;

delayms(200);

lcd_gotoxy(1,0);

lcd_string("Password:**");

while((PINA&0xf0)!=0xf0); //wait to release the key

while(PINA==0xff);

c=PINA;

delayms(200);

lcd_gotoxy(1,0);

lcd_string("Password:***");

while((PINA&0xf0)!=0xf0); //wait to release the key

while(PINA==0xff);

d=PINA;

delayms(200);

lcd_gotoxy(1,0);

lcd_string("Password:****");

while((PINA&0xf0)!=0xf0); //wait to release the key

while(PINA==0xff);

e=PINA;

delayms(200);

lcd_gotoxy(1,0);

lcd_string("Password:*****"); //wait to release the key

//checking the password

if(a==0xef)

{

if(b==0xdf)

{

if(c==0xbf)

{if(d==0x7f)

{

if(e==0xef)

{

lcd_init();

lcd_string("Welcome");

goto wait;

}

else

{

lcd_init();