Keyboard Serial

This example makes use of a Piezo Speaker in order to play tones. We are taking advantage of the processors capability to produde PWM signals in order to play music. There is more information about how PWM works written by David Cuartielles here and even at K3's old course guide

A Piezo is nothing but an electronic device that can both be used to play tones and to detect tones. In our example we are plugging the Piezo on the pin number 9, that supports the functionality of writing a PWM signal to it, and not just a plain HIGH or LOW value.

The tones can be lauched using any program able of sending ascii values over the serial port. Terminal software packages, Processing, Pure Data, Director, or the serial proxy + Flash combination can be used to launch the tones.

Example of connection of a Piezo to pin 9

```
/* Keyboard Serial
* ----------------
*
* Program to play tones depending on the
* data coming from the serial port.
*
* The calculation of the tones is made following the mathematical
* operation:
*
*       timeHigh = 1/(2 * toneFrequency) = period / 2
*
* where the different tones are described as in the table:
*
* note 	frequency 	period 	PW (timeHigh)
* c 	        261 Hz 	        3830 	1915
* d 	        294 Hz 	        3400 	1700
* e 	        329 Hz 	        3038 	1519
* f 	        349 Hz 	        2864 	1432
* g 	        392 Hz 	        2550 	1275
* a 	        440 Hz 	        2272 	1136
* b 	        493 Hz 	        2028	1014
* C	        523 Hz	        1912 	956
*
* (cleft) 2005 D. Cuartielles for K3
*/

int ledPin = 13;
int speakerOut = 9;
byte names[] ={'c', 'd', 'e', 'f', 'g', 'a', 'b', 'C'};
int tones[] = {1915, 1700, 1519, 1432, 1275, 1136, 1014, 956};
byte val = 0;
int serByte = -1;
int statePin = LOW;
int count = 0;

void setup() {
pinMode(ledPin, OUTPUT);
pinMode(speakerOut, OUTPUT);
beginSerial(9600);
}

void loop() {
digitalWrite(speakerOut, LOW);
if (serByte != -1) {
val = serByte;
printByte(val);
statePin = !statePin;
digitalWrite(ledPin, statePin);
}
for (count=0;count<=8;count++) {
if (names[count] == val) {
digitalWrite(speakerOut, HIGH);
delayMicroseconds(tones[count]);
digitalWrite(speakerOut, LOW);
delayMicroseconds(tones[count]);
}
}
}

```