Single-chip microcomputer | Use buzzer play music

The buzzer in the microcomputer can be controlled by setting its value repeatedly. However if we want to make it beep in a certain frequency, we need to do something more.

Here are some examples:

Für Elise

哈基米音乐

First, the value of frequency is measured by Herz (Hz). We denote the frequency of the buzzer as f. From the definition of frequency we have

$f={{1}\over {T}}$

where λ is the wave length of the sound wave. So we need to know the connection between λ and the change in the buzzer's input current.

We can see that in the picture, there are two change occurring within a period. So within a second, there would have to be ${{2} \over {T}} = 2f$ changes. For example, if we want to use buzzer simulate the note A at 440 Hz, there have to be 880 times of changes. So, it would take ${1} \over {880}$ second for every change.

So the code would be like:

#include <reg52.h>

#define uint unsigned int

#define uchar unsigned char

sbit BEEP = P2^5;

void delay(uint tus) {

while (tus--);

}

int play(int i, int ws){

while (i--) {

BEEP = !BEEP;

delay(ws);

}

i=0;

return 0;

}

void note(float s, float p)

float i = 50000/p;

play((int)s*p*0.22,(int)i);

}

When we want to  make the buzzer beep at a $f$ Hz for t seconds, call the note() function. The bigger the first parameter is, the longer this sound would last. And the higher value of the second parameter, the higher pitch it would be.