Презентация на тему Simple Digital and Analog Inputs

sense digital and analog inputs allows it to respond

to you and to the world around you

Digital input pins sense the presence and absence of voltage on a pin
Analog input pins measure a range of voltages on a pin

sketch if a voltage on a pin is HIGH

(5 volts) or LOW (0 volts)
pinMode(pin, INPUT) – configure pin as an INPUT
14 digital pins (numbered 0 to 13)
Pins 0 and 1 (marked RX and TX) are used for the USB serial connection
Need more?
Analog pins 0 through 5 can be used as digital pins 14 through 19

0 through 15 are digital pin numbers 54 through

69

make or break a connection
Single pole = only one

circuit is being controlled
Double pole = two circuits are being controlled at once
Single throw = only one path for circuit
Double throw = two potential paths for circuit

ball inside
Magnetic switches are delicate
The hex switch is actually

many switches in one, and outputs 4 signals

wants to see a voltage
Specifically, a “HIGH” (5 volts)

or a “LOW” (0 volts)
How do you go from make/break to HIGH/LOW?

digital inputs “float” between 0 & 5 volts (LOW

& HIGH)
Resistor “pulls” input to ground (0 volts)
Pressing switch “pushes” input to 5 volts
Press is HIGH
Not pressed is LOW

Pull-down resistor

up to the 5V line that the resistor is

connected to
pull-down resistors – pull the voltage down to 0 volts
Although 10K ohms is a commonly used value, anything between 4.7K and 20K or more will work

with a pull-down resistor
Turn on LED if button pressed

and OFF if released

to pin 2 lights the LED on pin 13

const

int ledPin = 13; // choose the pin for the LED
const int inputPin = 2; // choose the input pin (for a pushbutton)
void setup() {
pinMode(ledPin, OUTPUT); // declare LED as output
pinMode(inputPin, INPUT); // declare pushbutton as input
}
void loop(){
int val = digitalRead(inputPin); // read input value
If (val == HIGH) { // check if the input is HIGH
digitalWrite(ledPin, HIGH); // turn LED on if switch is pressed
} else {
digitalWrite(ledPin, LOW); // turn LED off
}
}

circuit.

push wires & components into holes

choose between actions, based on a data obtained from

switch-like sensor
E.g. “If motion is detected, turn on the lights”
E.g. “If flower pot soil is dry, turn on sprinklers”
Define actions, choose them from sensor inputs
Let’s try that with the actions we currently know
E.g.: If button is pressed send “Hello!” to serial port, and if released send “Goodbye!”

that can be enabled by writing a HIGH value

to a pin that is in INPUT mode

const int ledPin = 13;
const int inputPin = 2;
void setup() {
pinMode(ledPin, OUTPUT);
pinMode(inputPin, INPUT);
digitalWrite(inputPin,HIGH);
// turn on internal pull-up
}
void loop(){
int val = digitalRead(inputPin);
if (val == HIGH) {
digitalWrite(ledPin, HIGH);
} else {
digitalWrite(ledPin, LOW);
}
}

signals at the moment the switch contacts close or

open
avoid false readings due to contact bounce - debouncing

boolean debounce(int pin) {
boolean state;
boolean previousState;
previousState = digitalRead(pin); // store switch state
for(int cnt=0; cnt < debounceDelay; cnt++) {
delay(1); // wait for 1 millisecond
state = digitalRead(pin); // read the pin
if( state != previousState) {
cnt = 0; // reset the counter if the state changes
previousState = state; // and save the current state
}
}
return state;
}

states (or values, or “bins”) is resolution
Common computer resolutions:
8-bit

= 256 values
16-bit = 65,536 values
32-bit = 4,294,967,296 values

Analog to Digital Converter)
Reads voltage between 0 to 5

volts
Resolution is 10-bit (1024 values)
In other words, 5/1024 = 4.8 mV smallest voltage change you can measure

varying voltage?
With a potentiometer. (pot)

arrow taps the voltage on the resistor
When a resistor

goes across a voltage difference, like +5V to Gnd, the voltage measured at any point along a resistor’s length is proportional to the distance from one side.

ranged input
Measure rotational position
steering wheel, robotic joint, etc.
But more

importantly for us, potentiometers are a good example of a resistive sensor

plug into +5V & Gnd (red + & blue

-) buses
Middle “post” plugs into a row (row 7 here)
Run a wire from that row to Analog In 2