Arduino uno User Manual

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void loop() {
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}
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void output_result(const long result) {
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digitalWrite(LED_BIT0, result & B001);
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digitalWrite(LED_BIT1, result & B010);
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digitalWrite(LED_BIT2, result & B100);
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}
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This is all the code we need to implement the first version of a binary die. As
usual, we define some constants for the output pins the LEDs are connected
to. In the setup function, we set all the pins into OUTPUT mode. For the die, we
need random numbers in the range from one to six. The random function
returns random numbers in a specified range using a pseudorandom number
generator. In line 10, we initialize the generator with some noise we read from
analog input pin A0. (See Generating Random Numbers, on page 48, to learn
why we have to do that.) You might wonder where the constant A0 is from.
The Arduino IDE defines constants for all analog pins named A0 , A1 , and so
on. Then we actually generate a new random number between one and six
and output it using the output_result function. (The seven in the call to random
is correct, because it expects the upper limit plus one.)
The function output_result takes a number and outputs its lower three bits by
switching on or off our three LEDs accordingly. Here we use the & operator
and binary literals. The & operator takes two numbers and combines them
bitwise. When two corresponding bits are 1, the result of the & operator is 1,
too. Otherwise, it is 0. The B prefix allows you to put binary numbers directly
into your source code. For example, B11 is the same as 3 .
You might have noticed that the loop function was left empty, and you might
wonder how such a die works. It’s pretty simple: whenever you restart the
Arduino, it outputs a new number, and to roll the die again, you have to press
the reset button.
Compile the code, upload it to the Arduino, and play with your binary die.
You have mastered your first advanced electronics project! Enjoy it for a
moment!
Whenever you want to see a new result, you have to reset the Arduino. That’s
probably the most pragmatic user interface you can build, and for a first
prototype, this is okay. But it’s more elegant to control the dice with your
own button. That’s what we’ll do in the next section.
report erratum • discuss
First Version of a Binary Die • 47
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Arduino uno Specifications

General

Form factor	Arduino
Certification	RoHS, FC, CE
Processor model	-
Processor frequency	- MHz
Microcontroller model	ATmega328
Microcontroller frequency	16 MHz
DC input voltage	7-12 V
Operating voltage	5 V
DC current per I/O pin	40 mA
Flash memory	0.032 MB
Maximum internal memory	- GB
SRAM (Static Random Access Memory)	2 KB
EEPROM (Electrically Erasable Programmable Read-Only Memory)	1 KB
Wi-Fi	No
Number of analog I/O pins	6
Number of digital I/O pins	14

Weight and Dimensions

Board dimensions	53.4 x 68.6 mm