Sound Library

The mikroPascal PRO for 8051 provides a Sound Library to supply users with routines necessary for sound signalization in their applications. Sound generation needs additional hardware, such as piezo-speaker (example of piezo-speaker interface is given on the schematic at the bottom of this page).

External dependencies of Sound Library

The following variables must be defined in all projects using Sound Library:	Description:	Example :
`var Sound_Play_Pin: sbit; bdata; sfr; external;`	Sound output pin.	`var Sound_Play_Pin: sbit at P0_3_bit;`

Sound_Init

Prototype	procedure Sound_Init();
Returns	Nothing.
Description	Configures the appropriate MCU pin for sound generation.
Requires	`Sound_Play_Pin` variable must be defined before using this function.
Example	// Initialize the pin P0.3 for playing sound var Sound_Play_Pin : sbit at P0_3bit; ... Sound_Init();

Sound_Play

Prototype	procedure Sound_Play(var freq_in_Hz: word; var duration_ms: word);
Returns	Nothing.
Description	Generates the square wave signal on the appropriate pin. Parameters : `freq_in_Hz:` signal frequency in Hertz (Hz) `duration_ms:` signal duration in miliseconds (ms) Note: frequency range is limited by Delay_Cyc parameter. Maximum frequency that can be produced by this function is `Freq_max = Fosc/(803)`. Minimum frequency is `Freq_min = Fosc/(80255)`. Generated frequency may differ from the `freq_in_hz` parameter due to integer arithmetics.
Requires	In order to hear the sound, you need a piezo speaker (or other hardware) on designated port. Also, you must call Sound_Init to prepare hardware for output before using this function.
Example	// Play sound of 1kHz in duration of 100ms Sound_Play(1000, 100);

Library Example

The example is a simple demonstration of how to use the Sound Library for playing tones on a piezo speaker.

program Sound;

// Sound connections
var Sound_Play_Pin : sbit at P0_3_bit;
// End Sound connections


procedure Tone1();
  begin
    Sound_Play(659, 250);                      // Frequency = 659Hz, duration = 250ms
  end;

procedure Tone2() ;
  begin
    Sound_Play(698, 250);                      // Frequency = 698Hz, duration = 250ms
  end;

procedure Tone3() ;
  begin
    Sound_Play(784, 250);                      // Frequency = 784Hz, duration = 250ms
  end;

procedure Melody() ;                              // Plays the melody "Yellow house"
  begin
    Tone1(); Tone2(); Tone3(); Tone3();
    Tone1(); Tone2(); Tone3(); Tone3();
    Tone1(); Tone2(); Tone3();
    Tone1(); Tone2(); Tone3(); Tone3();
    Tone1(); Tone2(); Tone3();
    Tone3(); Tone3(); Tone2(); Tone2(); Tone1();
  end;

procedure ToneA() ;                  // Tones used in Melody2 function
  begin
    Sound_Play(880, 50);
  end;

procedure ToneC() ;
  begin
    Sound_Play(1046, 50);
  end;
procedure ToneE() ;
  begin
    Sound_Play(1318, 50);
  end;

procedure Melody2() ;                // Plays Melody2
var i : byte;
begin
i := 1;
while (i < 9) do
   begin
     ToneA();
     ToneC();
     ToneE();
     Inc(i);
   end;
end;

  begin
    P1 := 255;                     // Configure PORT1 as input
    Sound_Init();                  // Initialize sound pin

    Sound_Play(2000, 1000);        // Play starting sound, 2kHz, 1 second

    while TRUE do                    // endless loop
      begin
        if (P1_7 = 0) then                // If P1.7 is pressed play Tone1
            begin
              Tone1();
              while ( P1_7 = 0) do nop ;           // Wait for button to be released
          end;

        if ( P1_6 = 0) then                // If P1.6 is pressed play Tone2
          begin
            Tone2();                  //
            while ( P1_6 = 0) do nop;           // Wait for button to be released
          end;

        if ( P1_5 = 0) then                // If P1.5 is pressed play Tone3
          begin
            Tone3();                  //
            while ( P1_5 = 0) do nop ;           // Wait for button to be released
          end;

        if ( P1_4 = 0 ) then                // If P1.4 is pressed play Melody2
          begin
            Melody2();                //
            while ( P1_4 = 0 ) do nop;           // Wait for button to be released
          end;

        if ( P1_3 = 0) then                // If P1.3 is pressed play Melody
          begin
            Melody();                 //
            while ( P1_3 = 0 ) do nop;           // Wait for button to be released
          end;
      end;
  end.

HW Connection

Example of Sound Library connection

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