Digital & Analog Inputs

Review

• Fundamental parts of an Arduino program are …

• Setting output types using pinMode.• Declaring variables• Can write a digital signal (0/1) to a pin

using digitalWrite.• Can read a digital signal (0/1) from a pin

using digitalRead.– Must have a variable to store the value

IF, IF-ELSE, and IF-ELSE-IFif (someCondition) {

// do stuff if the condition is true }

if (someCondition) {

// do stuff if the condition is true } else {

// do stuff if the condition is false }

if (someCondition) {

// do stuff if the condition is true } else if (anotherCondition) {

// do stuff only if the first condition is false // and the second condition is true

}

Your turn

• Challenges: Complete in order1. Push the button and have it display an LED pattern

• Fireworks!

2. Push the button and have it turn on alternate LEDs• Button HIGH – Yellow• Button LOW – Red

3. Push the button twice to turn on LED• Need a COUNTER -- if you get to this stage, ask one of us for

help

ANALOG INPUTS

Analog Signals

• What is an analog signal and how does it differ from a digital signal?

1 1 1 1 1 000

Analog Signals & Arduinos

• The Arduino can read an analog signal on one of the analog input pins.– analogRead

• The signal that can be read must be between 0 and 5 V.

• The Arduino converts the signal to a number between 0 and 1023.

• How many values are there for a digital signal? How many values are there for an analog signal on the Arduino?

Analog Input

Program Time!

• We’re going to write a program that will turn on the Arduino’s LED when “threshold” value is reached.

How:

Potentiometer

•Use a Voltage Divider to change the voltage on the analog input pin. •Use the Arduino to detect when the voltage has reached a certain level.•Turn on the LED!

Analog Signal Detector• Step 1 – Declare Variables:

int inputPin = 0; // select the input pin for the potentiometer // ( can be 0 through 5).

int ledPin = 13; // select the pin for the Arduino’s LED int inputValue = 0; // variable to store the value coming from

// the voltage divider.• Step 2 – Setup:

void setup(){

pinMode(ledPin, OUTPUT); //Declare the LED pin as an //output.}

• We do NOT have to declare the analog pin as an input. Why?

Analog Signal Detector• Step 3 – The Loop:

void loop() {

inputValue = analogRead(inputPin); // Read the analog //input, what are// the possible values.

if(inputValue > 511) // Check our threshold.{

digitalWrite(ledPin, HIGH); // Turn on the LED.}else{

digitalWrite(ledPin, LOW); // Turn off the LED.}

}

Your turn

• Challenges: Complete in order1. Design a program to make the LED flash at a

speed dependent on the value on the analog input pin.

2. Turn on a number of LEDs that is proportional to the analog input value.