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Lesson 13 Button Pianoο
Introductionο
In our past lesson, we learned how to use PWM waves to drive a passive buzzer to ring. In this lesson, we make a simple keyboard by applying a passive buzzer. Letβs get started!
Newly Added Componentsο
Schematic Diagramο
Build the Circuitο
For C Language Usersο
Commandο
1. Go to the folder of the code.
cd /home/pi/electronic-kit/for-raspberry-pi/c/Lesson_13_Button_Piano
2. Compile the code.
gcc 13_ButtonPiano.c -lwiringPi
3. Run the executable file.
sudo ./a.out
Now press the seven buttons, and the buzzer will emit the notes: DO, RE, MI, FA, SO, LA, TI. You can play a song with these seven buttons.
Note
If it does not work after running, or there is an error prompt: "wiringPi.h: No such file or directory", please refer to C code is not working?.
Codeο
#include <wiringPi.h>
#include <softTone.h>
#include <stdio.h>
#define BuzPin 0
const int Tone[] = {262,294,330,350,393,441,495};//define DO, RE, MI, FA, SO, LA, TI
int beat[] = {1,1,1,1,1,1,1};
const int Btn[] = {2,3,4,5,6,10,11};//define 7 buttons
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;
}
//set the buttons mode
for(int j=0;j<7;j++)
{
pinMode(Btn[j], INPUT);
}
while(1){
//printf("Please press button to play the piano\n");
// Indicate that button has pressed down
for(i=0;i<7;i++)
{
if(digitalRead(Btn[i])==1)
{
delay(10);//Prevent the button' s vibration
if(digitalRead(Btn[i])==1)
{
softToneWrite(BuzPin, Tone[i]);
delay(beat[i]*250);
printf("1");
}
}
else
softToneWrite(BuzPin, 0);
if(i==7)
i=0;
}
}
return 0;
}
Code Explanationο
7. const int Tone[] = {262,294,330,350,393,441,495};
8. int beat[] = {1,1,1,1,1,1,1};
In the array Tone[], define the frequencies of DO, RE, MI, FA, SO, LA, TI and the number in beat[] refers to the beat of each note in this song(0.5s for each beat).
26. for(int j=0;j<7;j++)
27. {
28. pinMode(Btn[j], INPUT);
29. }
Set the mode of all buttons to input mode in the for loop.
34. for(i=0;i<7;i++)
35. {
36. if(digitalRead(Btn[i])==1)
37. {
38. delay(10);//Prevent the button' s vibration
39. if(digitalRead(Btn[i])==1)
40. {
41. softToneWrite(BuzPin, Tone[i]);
42. delay(beat[i]*250);
43. printf("1");
44. }
45. }
Use a for loop to check all the buttons. When one button in array Btn[i] is detected to be pressed, the buzzer will respond to the corresponding note in array Tone[i].
46. else
47. softToneWrite(BuzPin, 0);
48. if(i==7)
49. i=0;
50. }
If no button is pressed, turn off the buzzer.
For Python Language Usersο
Commandο
1. Go to the folder of the code.
cd /home/pi/electronic-kit/for-raspberry-pi/python
2. Run the code.
sudo python3 13_ButtonPiano.py
Now press the seven buttons, and the buzzer will emit the notes: DO, RE, MI, FA, SO, LA, TI. You can play a song with these seven buttons.
Codeο
Note
You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like electronic-kit/for-raspberry-pi/python. After modifying the code, you can run it directly to see the effect.
import RPi.GPIO as GPIO
import time
Buzzer = 17
BtnPin = [18,27,22,23,24,25,8,7]
CL = [0, 131, 147, 165, 175, 196, 211, 248] # Frequency of Low C notes
CM = [0, 262, 294, 330, 350, 393, 441, 495] # Frequency of Middle C notes
CH = [1, 525, 589, 661, 700, 786, 882, 990] # Frequency of High C notes
song = [ 0,CM[1],CM[2],CM[3],CM[4],CM[5],CM[6],CM[7] ]
beat = [ 1,1, 1, 1, 1, 1, 1, 1]
def setup():
GPIO.setmode(GPIO.BCM)
for i in range(1, len(BtnPin)):
GPIO.setup(BtnPin[i],GPIO.IN)
GPIO.setup(Buzzer, GPIO.OUT)
def loop():
global Buzz
while True:
#print ('\n Please playing piano...')
for i in range(1, len(BtnPin)):
if GPIO.input(BtnPin[i]) == 1:
Buzz = GPIO.PWM(Buzzer, song[i])
Buzz.start(50)
time.sleep(beat[i] * 0.25)
Buzz.stop()
def destory():
Buzz.stop()
GPIO.output(Buzzer, 0)
GPIO.cleanup()
if __name__ == '__main__': # Program start from here
setup()
try:
loop()
except KeyboardInterrupt: # When 'Ctrl+C' is pressed, the child program destroy() will be executed.
destory()
Code Explanationο
7.CL = [0, 131, 147, 165, 175, 196, 211, 248] # Frequency of Low C notes
8.CM = [0, 262, 294, 330, 350, 393, 441, 495] # Frequency of Middle C notes
9.CH = [1, 525, 589, 661, 700, 786, 882, 990] # Frequency of High C notes
These are the frequencies of each note. The first 0 is to skip CL[0] so that the number CL[1]-CL[7] corresponds to the CDEFGAB of the note.
10.song = [ 0,CM[1],CM[2],CM[3],CM[4],CM[5],CM[6],CM[7] ]
11.beat = [ 1,1, 1, 1, 1, 1, 1, 1]
Define a section of music and the corresponding beats. The number in beat[] refers to the beat of each note in the song(0.5s for each beat).
16. for i in range(1, len(BtnPin)):
17. GPIO.setup(BtnPin[i],GPIO.IN)
Set the mode of all buttons to input mode in the for loop.
24. for i in range(1, len(BtnPin)):
25. if GPIO.input(BtnPin[i]) == 1:
26. Buzz = GPIO.PWM(Buzzer, song[i])
27. Buzz.start(50)
28. time.sleep(beat[i] * 0.25)
29. Buzz.stop()
Use a for loop to check all the buttons. When one button in array button[i] is detected to be pressed, the buzzer will respond to the corresponding note in array song[i].
Phenomenon Pictureο
