How to generate sound using 8051 microcontroller (AT89C51)- (Part 18/45)

This article explains the concept behind generating sound from the 8051 microcontroller (AT89C51). This concept can be used to generate sound with any MCU. It can be used to generate specific sounds or alarms. This circuit has wide applications like in cars to produce sound while reversing, in electronic piano to generate different tones, or in electronic toys to generate tones.

Sound is a function of frequency. This concept has been used to generate sound from the microcontroller. Different types of sounds can be produced by varying the frequency.

Frequencies are generated by using Timer1 of microcontroller. Timer is used to produce exact delays and by toggling the output pin we can generate the desired frequencies. These frequencies are then fed to a particular pin (here Pin 0 of port1) which is connected to speaker. The output can be heard on the speaker. By combining the different frequencies we can generate different tones and alarms.

Project Source Code

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// Program to generate different sounds using micro controller

#include<reg51.h>
sbit out=P1^0;  //output pin 1

void delay(unsigned char p,unsigned char q)
{
TMOD=0x01;  //timer0 mode1(16 bit)
TL0=q;      //load TL0
TH0=p;      //load TH0
TR0=1;   //turn on T0
while(TF0==0); // wait for flag generation
TR0=0;   // turn off T0
TF0=0;    // clear TF0
}

void play(unsigned char j,unsigned char k)
{
int i;
for(i=0;i<1000;i++)  //to play sound
{
  out=1;
  delay(j,k);
  out=0;
  delay(j,k);
}
}

void main()
{
int l;
while(1)
{
  play(0xfc,0x66);  //playing sound of frequency of about 500 hertz with a delay between two frequencies
  for(l=0;l<5;l++)   
  {
   delay(0x00,0x00);  //delay of 71 miliseconds
  }
  play(0xfe,0x33);  //playing sound of frequency of about 1000 hertz with a delay between two frequencies
  for(l=0;l<5;l++)
  {
   delay(0x00,0x00);  
  }
  play(0xff,0xa3);  //playing sound of frequency of about 5000 hertz with a delay between two frequencies
  for(l=0;l<5;l++)
  {
   delay(0x00,0x00);  
  }
  play(0xff,0xd1);  //playing sound of frequency of about 10000 hertz with a delay between two frequencies
  for(l=0;l<5;l++)
  {
   delay(0x00,0x00);  
  }
  play(0xff,0xdc);  //playing sound of frequency of about 13000 hertz with a delay between two frequencies
  for(l=0;l<5;l++)
  {
   delay(0x00,0x00);  
  }
  play(0xff,0xcc);  //playing sound of frequency of about 9300 hertz with a delay between two frequencies
  for(l=0;l<5;l++)
  {
   delay(0x00,0x00);  
  }
  play(0xff,0xe8);  //playing sound of frequency of about 20000 hertz with a delay between two frequencies
  for(l=0;l<5;l++)
  {
   delay(0x00,0x00);  
  }
} 
}

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