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1.2.2 Passive Buzzer
=====================

Introduction
------------

In this lesson, we will learn how to make a passive buzzer play music.

Components
----------

.. image:: img/list_1.2.2.png


Schematic Diagram
-----------------

In this experiment, a passive buzzer, a PNP transistor and a 1k resistor
are used between the base of the transistor and GPIO to protect the
transistor.

When GPIO17 is given different frequencies, the passive buzzer will emit
different sounds; in this way, the buzzer plays music.

.. image:: img/image333.png


Experimental Procedures
-----------------------

**Step 1**: Build the circuit.

.. image:: img/image106.png
    :width: 800



For C Language Users
^^^^^^^^^^^^^^^^^^^^

**Step 2**: Change directory.

.. raw:: html

   <run></run>

.. code-block::

    cd ~/davinci-kit-for-raspberry-pi/c/1.2.2/

**Step 3**: Compile.

.. raw:: html

   <run></run>

.. code-block::

    gcc 1.2.2_PassiveBuzzer.c -lwiringPi

**Step 4**: Run.

.. raw:: html

   <run></run>

.. code-block::

    sudo ./a.out

The code run, the buzzer plays a piece of music.

.. note::

    If it does not work after running, or there is an error prompt: \"wiringPi.h: No such file or directory\", please refer to :ref:`install_wiringpi`.

**Code**

.. code-block:: c

    #include <wiringPi.h>
    #include <softTone.h>
    #include <stdio.h>

    #define BuzPin    0

    #define  CL1  131
    #define  CL2  147
    #define  CL3  165
    #define  CL4  175
    #define  CL5  196
    #define  CL6  221
    #define  CL7  248

    #define  CM1  262
    #define  CM2  294
    #define  CM3  330
    #define  CM4  350
    #define  CM5  393
    #define  CM6  441
    #define  CM7  495

    #define  CH1  525
    #define  CH2  589
    #define  CH3  661
    #define  CH4  700
    #define  CH5  786
    #define  CH6  882
    #define  CH7  990

    int song_1[] = {CM3,CM5,CM6,CM3,CM2,CM3,CM5,CM6,CH1,CM6,CM5,CM1,CM3,CM2,
                    CM2,CM3,CM5,CM2,CM3,CM3,CL6,CL6,CL6,CM1,CM2,CM3,CM2,CL7,
                    CL6,CM1,CL5};

    int beat_1[] = {1,1,3,1,1,3,1,1,1,1,1,1,1,1,3,1,1,3,1,1,1,1,1,1,1,2,1,1,
                    1,1,1,1,1,1,3};


    int song_2[] = {CM1,CM1,CM1,CL5,CM3,CM3,CM3,CM1,CM1,CM3,CM5,CM5,CM4,CM3,CM2,
                    CM2,CM3,CM4,CM4,CM3,CM2,CM3,CM1,CM1,CM3,CM2,CL5,CL7,CM2,CM1
                    };

    int beat_2[] = {1,1,1,3,1,1,1,3,1,1,1,1,1,1,3,1,1,1,2,1,1,1,3,1,1,1,3,3,2,3};

    int main(void)
    {
        int i, j;
        if(wiringPiSetup() == -1){ //when initialize wiring failed,print message to screen
            printf("setup wiringPi failed !");
            return 1;
        }

        if(softToneCreate(BuzPin) == -1){
            printf("setup softTone failed !");
            return 1;
        }

        while(1){
            printf("music is being played...\n");
            delay(100);
            for(i=0;i<sizeof(song_1)/4;i++){
                softToneWrite(BuzPin, song_1[i]);   
                delay(beat_1[i] * 500);
            }

            for(i=0;i<sizeof(song_2)/4;i++){
                softToneWrite(BuzPin, song_2[i]);   
                delay(beat_2[i] * 500);
            }   
        }

        return 0;
    }

**Code Explanation**

.. code-block:: c

    #define  CL1  131
    #define  CL2  147
    #define  CL3  165
    #define  CL4  175
    #define  CL5  196
    #define  CL6  221
    #define  CL7  248

    #define  CM1  262
    #define  CM2  294


These frequencies of each note are as shown. CL refers to low note, 
CM middle note, CH high note, 1-7 correspond to the notes C, D, E, F, G, A, B.

.. code-block:: c

    int song_1[] = {CM3,CM5,CM6,CM3,CM2,CM3,CM5,CM6,CH1,CM6,CM5,CM1,CM3,CM2,
                    CM2,CM3,CM5,CM2,CM3,CM3,CL6,CL6,CL6,CM1,CM2,CM3,CM2,CL7,
                    CL6,CM1,CL5};
    int beat_1[] = {1,1,3,1,1,3,1,1,1,1,1,1,1,1,3,1,1,3,1,1,1,1,1,1,1,2,1,1,
                    1,1,1,1,1,1,3};

The array, song_1[] stores a musical score of a song in which beat_1[] 
refers to the beat of each note in the song (0.5s for each beat).

.. code-block:: c

    if(softToneCreate(BuzPin) == -1){
            printf("setup softTone failed !");
            return 1;
        
This creates a software controlled tone pin. You can use any GPIO pin 
and the pin numbering will be that of the wiringPiSetup() function 
you used. The return value is 0 for success. Anything else and you 
should check the global errnovariable to see what went wrong.

.. code-block:: c

    for(i=0;i<sizeof(song_1)/4;i++){
        softToneWrite(BuzPin, song_1[i]);   
        delay(beat_1[i] * 500);
    }

Employ a for statement to play song_1.

In the judgment condition, **i<sizeof(song_1)/4**\ ，“devide by 4” is
used because the array song_1[] is an array of the data type of integer,
and each element takes up four bytes.

The number of elements in song_1 (the number of musical notes) is gotten
by deviding sizeof(song_4) by 4.

To enable each note to play for beat \* 500ms, the function
delay(beat_1[i] \* 500) is called.

The prototype of softToneWrite(BuzPin, song_1[i])：

.. code-block:: c

    void softToneWrite (int pin, int freq);

This updates the tone frequency value on the given pin. The tone 
does not stop playing until you set the frequency to 0.

For Python Language Users
^^^^^^^^^^^^^^^^^^^^^^^^^

**Step 2: Change directory.**

.. raw:: html

   <run></run>

.. code-block::

    cd ~/davinci-kit-for-raspberry-pi/python/

**Step 3: Run.**

.. raw:: html

   <run></run>

.. code-block::

    sudo python3 1.2.2_PassiveBuzzer.py

The code run, the buzzer plays a piece of music.

**Code**

.. note::

    You can **Modify/Reset/Copy/Run/Stop** the code below. But before that, you need to go to  source code path like ``davinci-kit-for-raspberry-pi/python``. 
    
.. raw:: html

    <run></run>

.. code-block:: python

    import RPi.GPIO as GPIO
    import time

    Buzzer = 11

    CL = [0, 131, 147, 165, 175, 196, 211, 248]		# Frequency of Bass tone in C major

    CM = [0, 262, 294, 330, 350, 393, 441, 495]		# Frequency of Midrange tone in C major

    CH = [0, 525, 589, 661, 700, 786, 882, 990]		# Frequency of Treble tone in C major

    song_1 = [	CM[3], CM[5], CM[6], CM[3], CM[2], CM[3], CM[5], CM[6], # Notes of song1
                CH[1], CM[6], CM[5], CM[1], CM[3], CM[2], CM[2], CM[3], 
                CM[5], CM[2], CM[3], CM[3], CL[6], CL[6], CL[6], CM[1],
                CM[2], CM[3], CM[2], CL[7], CL[6], CM[1], CL[5]	]

    beat_1 = [	1, 1, 3, 1, 1, 3, 1, 1, 			# Beats of song 1, 1 means 1/8 beat
                1, 1, 1, 1, 1, 1, 3, 1, 
                1, 3, 1, 1, 1, 1, 1, 1, 
                1, 2, 1, 1, 1, 1, 1, 1, 
                1, 1, 3	]

    song_2 = [	CM[1], CM[1], CM[1], CL[5], CM[3], CM[3], CM[3], CM[1], # Notes of song2
                CM[1], CM[3], CM[5], CM[5], CM[4], CM[3], CM[2], CM[2], 
                CM[3], CM[4], CM[4], CM[3], CM[2], CM[3], CM[1], CM[1], 
                CM[3], CM[2], CL[5], CL[7], CM[2], CM[1]	]

    beat_2 = [	1, 1, 2, 2, 1, 1, 2, 2, 			# Beats of song 2, 1 means 1/8 beat
                1, 1, 2, 2, 1, 1, 3, 1, 
                1, 2, 2, 1, 1, 2, 2, 1, 
                1, 2, 2, 1, 1, 3 ]

    def setup():

        GPIO.setmode(GPIO.BOARD)		# Numbers GPIOs by physical location
        GPIO.setup(Buzzer, GPIO.OUT)	# Set pins' mode is output
        global Buzz						# Assign a global variable to replace GPIO.PWM 
        Buzz = GPIO.PWM(Buzzer, 440)	# 440 is initial frequency.
        Buzz.start(50)					# Start Buzzer pin with 50% duty cycle

    def loop():
        while True:
            print ('\n    Playing song 1...')
            for i in range(1, len(song_1)):		# Play song 1
                Buzz.ChangeFrequency(song_1[i])	# Change the frequency along the song note
                time.sleep(beat_1[i] * 0.5)		# delay a note for beat * 0.5s
            time.sleep(1)						# Wait a second for next song.

            print ('\n\n    Playing song 2...')
            for i in range(1, len(song_2)):     # Play song 1
                Buzz.ChangeFrequency(song_2[i]) # Change the frequency along the song note
                time.sleep(beat_2[i] * 0.5)     # delay a note for beat * 0.5s

    def destory():
        Buzz.stop()                 # Stop the buzzer
        GPIO.output(Buzzer, 1)      # Set Buzzer pin to High
        GPIO.cleanup()				# Release resource

    if __name__ == '__main__':		# Program start from here
        setup()
        try:
            loop()
        except KeyboardInterrupt:  	# When 'Ctrl+C' is pressed, the program destroy() will be executed.
            destory()

**Code Explanation**

.. code-block:: python

    CL = [0, 131, 147, 165, 175, 196, 211, 248]     # Frequency of Bass tone in C major
    CM = [0, 262, 294, 330, 350, 393, 441, 495]     # Frequency of Midrange tone in C major
    CH = [0, 525, 589, 661, 700, 786, 882, 990]     # Frequency of Treble tone in C major     

These are the frequencies of each note. The first 0 is to 
skip CL[0] so that the number 1-7 corresponds to the CDEFGAB of the tone.

.. code-block:: python

    song_1 = [  CM[3], CM[5], CM[6], CM[3], CM[2], CM[3], CM[5], CM[6], 
                CH[1], CM[6], CM[5], CM[1], CM[3], CM[2], CM[2], CM[3],
                CM[5], CM[2], CM[3], CM[3], CL[6], CL[6], CL[6], CM[1],
                CM[2], CM[3], CM[2], CL[7], CL[6], CM[1], CL[5] ]

These arrays are the notes of a song.

.. code-block:: python

    beat_1 = [  1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1,
                1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1,
                1, 1, 3 ]

Every sound beat (each number) represents the ⅛ beat, or 0.5s

.. code-block:: python

    Buzz = GPIO.PWM(Buzzer, 440)
    Buzz.start(50)  

Define pin Buzzer as PWM pin, then set its frequency to 440 and 
Buzz.start(50) is used to run PWM. What’s more, set the duty cycle to 50%.

.. code-block:: python

    for i in range(1, len(song_1)): 
                Buzz.ChangeFrequency(song_1[i]) 
                time.sleep(beat_1[i] * 0.5)  

Run a for loop, then the buzzer will play the notes in the array song_1[] 
with the beats in the beat_1[] array, .

Now you can hear the passive buzzer playing music.

Phenomenon Picture
------------------

.. image:: img/image107.jpeg