Arduino uno User Manual

For uploading software, the Arduino has a serial port, and you can use it to
connect the Arduino to other devices, too. (In Compiling and Uploading Pro-
grams, on page 19, you learned how to look up the serial port your Arduino
is connected to.) In this section, you’ll use the serial port to control Arduino’s
status LED using your computer’s keyboard. The LED should be turned on
when you press 1, and it should be turned off when you press 2. Here’s all
the code you need:
Welcome/LedSwitch/LedSwitch.ino
const unsigned int LED_PIN = 13;
Line 1
const unsigned int BAUD_RATE = 9600;
-
-
void setup() {
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pinMode(LED_PIN, OUTPUT);
5
Serial.begin(BAUD_RATE);
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}
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void loop() {
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if (Serial.available() > 0) {
10
int command = Serial.read();
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if (command == '1') {
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digitalWrite(LED_PIN, HIGH);
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Serial.println("LED on");
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} else if (command == '2') {
15
digitalWrite(LED_PIN, LOW);
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Serial.println("LED off");
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} else {
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Serial.print("Unknown command: ");
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Serial.println(command);
20
}
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}
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}
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As in our previous examples, we define a constant for the pin the LED is
connected to and set it to OUTPUT mode in the setup function. In line 6, we ini-
tialize the serial port using the begin function of the Serial class, passing a baud
rate of 9600. (You can learn what a baud rate is in Learning More About
Serial Communication, on page 253.) That’s all we need to send and receive
data via the serial port in our program.
So, let’s read and interpret the data. The loop function starts by calling Serial ’s
available method in line 10. available returns the number of bytes waiting on the
serial port. If any data is available, we read it using Serial.read . read returns the
first byte of incoming data if data is available and -1 otherwise.
If the byte we have read represents the character 1, we switch on the LED
and send back the message “LED on” over the serial port. We use Serial.println ,
report erratum • discuss
Using Serial Ports • 29
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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