Thames & Kosmos Code Gamer - PROJECT 12: Siren; THE PROGRAM

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Siren
Now it’s time to bring some order to the acoustic chaos.
This project will let you make your KosmoDuino howl like
a siren.
YOU WILL NEED
› KosmoDuino in the interaction board
Here’s where you specify the frequency range within
which the sound pitch is to move.
FREQ_MIN
corresponds
to the deepest sound of the siren, and
FREQ_MAX
the
highest. You can also experiment with these parameters
by changing the values, and find a siren noise to suit your
taste.
DELAY
determines how long any given sound will be held.
The variable
freq
finally, saves the current frequency.
The siren starts at
FREQ_MIN
.
#include <KosmoBits_Pins.h>
const int buzzerPin = KOSMOBITS_BUZZER_PIN;
const int FREQ_MIN = 440;
const int FREQ_MAX = 660;
const int DELAY = 4;
int freq = FREQ_MIN; // Frequency of the sound
// that is output.
void setup() {
// Nothing to do here.
}
void loop() {
tone(buzzerPin, freq); // (1)
del ay(DEL AY);
++freq; // Short for: freq = freq + 1;
if (freq > FREQ_MAX) {
freq = FREQ_MIN;
}
}
This time, you won’t have to do anything in
s e tu p()
.
The main loop starts by outputting a sound with the
frequency
freq
(1). After a pause of length
DELAY
, the
frequency
freq
is raised by 1 with
++freq;
. The
if
instruction then checks whether the maximum frequency
has been exceeded. If so, the frequency
freq
is returned to
the starting value
FREQ_MIN
.
In the next project, you will be producing an entire musical
scale. But first you will have to learn about an important
programming tool: Arrays.
THE PLAN
With every pass through the main loop, a new sound will
be output. Each time, the pitch will be raised a little. Once
a certain frequency, or sound pitch, is attained, the pitch
drops back to its starting value and the whole thing starts
over from the beginning.
THE PROGRAM

PROJECT 12
CodeGamer manual inside english.indd 40 7/19/16 12:32 PM