Arduino Uno Quick Start Manual page 93

• Blinking LEDs are great, but when we think of Morse code, we usually
think of beeping sounds, so replace the LED with a piezo speaker, which
is cheap and easy to use. The following figure shows how you connect it
to an Arduino. Piezo speakers have a ground pin and a signal pin, so
connect the speaker s ground to the Arduino s ground, and connect the
signal pin to Arduino pin 13.
Then replace the output_symbol
void Telegraph::output_symbol(const int
const int frequency = 131;
tone(_output_pin, frequency, length);
This sends a square wave to the speaker, and it plays a tone having a
frequency of 131 Hertz. (Look at the example under File > Examples >
02.Digital > toneMelody that comes with the Arduino IDE to learn more
about playing notes with a piezo speaker.)
• The Arduino IDE offers an alternative way to handle serial communication.
Have a look at Serial Communication Using Various Languages, on page
255, and rewrite the Morse code library so that it uses the new
function. Also, use String
• Improve the library s design to make it easier to support different output
devices. You could pass some kind of
constructor. Then derive a
could look as follows:
class OutputDevice {
public:
virtual void output_symbol(const int
};
class Led : public OutputDevice {
Chapter 4. Building a Morse Code Generator Library
method with the following code:
length) {
objects instead of character arrays.
OutputDevice
LedDevice and a SpeakerDevice
length);
www.it-ebooks.info
74
serialEvent
object to the Telegraph
from OutputDevice . It
report erratum discuss