11: Music Experiment

#Basic knowledge
Speaker, commonly known as horn, is a generator that can emit a variety of audio frequencies and is widely used in real life.

Sound-generating principle:

The production of sound is an effect of audio vibration. A high frequency of vibration is a high pitch, and a low frequency is a low pitch.
The range of audio is 20Hz-200kHz. The sound that human ears can easily identify is about 200Hz-20kHz.
In general, the audio circuit drives the speaker with a sine wave signal to produce pleasant music; in digital circuits, the speaker is generally driven by a pulse signal to produce sound, and the effect is relatively worse.


1) Tone
Do, Re, Mi, Fa, So, La, St represent a certain frequency of sound, which is called "tone".
2) Beat
The beat can make music melody (fixed rhythm), and can also adjust the speed of each sound. "Beat" is Beat.
C3/4 represents C key, 4 bars, and three beats per bar; one bar is between two straight lines.
If the speed of each bar is 1.5s, it means 0.5s per beat, 0.375s for 3/4 beats, 0.25s for 1/2 beats, 0.125s for 1/4 beats... and so on.

3) The contrast between the C scale and frequency.

#experiment

1) Definition of frequency table
Frequency table data

2) Audio playback table

3) Program flow

C Code

**********************************************************************/

* 【Course 12】 ****Music Experiment***********

* 【illustrate】 ****

* 【Description】 ****Experiment on the Happy Birthday song.

**********************************************************************/

/*---------------------------------------------

51 single chip microcomputer music playing experiment

-----------------------------------------------*/

#include //51 header file,

//---------Two commonly used macro definitions-------------- 

#define uint8 unsigned char

#define uint16 unsigned int

sbit Music=P2^0;

uint16 code FreTab_Low[7]={262,294,330,349,392,440,494}; //Bass frequency table

uint16 code FreTab_Mid[7]={523,578,659,698,784,880,988}; //Mid-range frequency table

uint16 code FreTab_Hight[7]={1046,1175,1318,1397,1568,1760,1976}; //treble frequency table

/*-----------------------------------------------------

Music score storage format uchar code MusicName{pitch, note length, ...., 0,0};

End: 0,0 means the end.

The pitch is determined by the frequency, and the length of the note, that is, the beat, can be set by yourself. In this program,

Timer T1 is used for beat timing, and the timing time is 50ms. So in this score, 1 beat

Indicates 50ms.

-------------------------------------------------------*/

uint8 code Happy_Birthday[]={0x11,0x05,0x11,0x05,0x12,0x0a,0x11,0x0a,

0x14,0x0a,0x13,0x14,

0x11,0x05,0x11,0x05,0x12,0x0a,0x11,0x0a,

0x15,0x0a,0x14,0x14,

0x11,0x05,0x11,0x05,0x21,0x0a,0x16,0x0a,

0x14,0x0a,0x13,0x0a,0x22,0x0a,

0x17,0x05,0x17,0x05,0x16,0x0a,0x14,0x0a,

0x15,0x0a,0x14,0x14,0x00,0x00

};

uint16 Fre; //Variable to store the obtained frequency value

/*-----------------------------------------------

Function name: Timer_Init()

Function: Initialize two timers

Entry parameters: None

------------------------------------------------*/

void Timer_Init()

{

TMOD=0x11;

EA=1;

ET0=1;

ET1=0;

TR0=0;

TR1=0;

}

/*-----------------------------------------------

Function name: Timer0_Ser()

Function: The interrupt service routine of timer 0 is mainly used to generate the required frequency

          This drives the speaker to emit the corresponding note.

Entry parameters: None

------------------------------------------------*/

void Timer0_i() interrupt 1

{

TH0=Fre/256;

TL0=Fre%256;

if(Music==0)

Music=1;

else Music=0;

}

/*-----------------------------------------------

Function name: Music_Play(uchar *MusicTab)

Function: music playback function,

Entry parameter: *MusicTab The first address of the music to be played

------------------------------------------------*/

void Music_Play(uint8 *MusicTab)

{

uint8 *pMusic;

uint8 temp,i;

pMusic=MusicTab; //Give the first address of the song to the pointer variable

while(*pMusic!=0)

{

if((*pMusic&0xf0)==0x00)

Fre=65536-1000000/FreTab_Low[*pMusic&0x0f];

else if((*pMusic&0xf0)==0x10)

Fre=65536-1000000/FreTab_Mid[*pMusic&0x0f];

else if((*pMusic&0xf0)==0x20)

Fre=65536-1000000/FreTab_Hight[*pMusic&0x0f];

TH0=Fre/256; //Calculate the initial value of frequency and assign the high eight bits

TL0=Fre%256; //Calculate the initial value of frequency and assign the lower eight bits

TH1=0x3c; //Assign initial value to timer 1, set timer to 50ms

TL1=0xb0;

pMusic++; //Get the beat value

temp=*pMusic;

TR0=1; //Start timer T0

TR1=1; //Start timer T1

for(i=0;i {

while(TF1==0); //Judge whether timer 1 overflows

TH1=0x3c;

TL1=0xb0;

TF1=0;

}

pMusic++;

}

}

/*-----------------------------------------------

Function name: main()

Function: Main function

Entry parameters: None

------------------------------------------------*/

void main()

{

Timer_Init();

while(1)

{

Music_Play(Happy_Birthday);

}

}