arduino:arduino_crash_course:basic_interaction
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arduino:arduino_crash_course:basic_interaction [2012/11/03 21:12] – [Polling versus interrupts] mithat | arduino:arduino_crash_course:basic_interaction [2017/12/06 01:05] (current) – mithat | ||
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In an interrupt scheme, the microcontroller does essentially nothing in its main loop, but it is directed to do something specific when an input source jostles it into action. | In an interrupt scheme, the microcontroller does essentially nothing in its main loop, but it is directed to do something specific when an input source jostles it into action. | ||
- | Of the two, polling is probably easier to get started with. You can use both techniques | + | Of the two, polling is probably easier to get started with. We won't learn how to work with interrupts in this section, but it's good to know that you can use both techniques |
- | Following is a simple | + | ===== Polling |
- | ===== Switch-controlled | + | The following examples use polling to determine the state of a switch. If the switch is pressed, the Arduino will turn an LED on. If it is not pressed, it will turn the LED off. |
- | The following examples use polling to determine the state of a switch. If the switch is pressed, Arduino will turn an LED on. If it is not pressed, it will turn the LED off. | + | ==== With external pulldown resistors ==== |
- | + | ||
- | ==== Using external pulldown resistors ==== | + | |
The following example requires **pulldown resistors** on the input switch. | The following example requires **pulldown resistors** on the input switch. | ||
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int pushButtonPin = 2; // connect the push button to digital pin 2 | int pushButtonPin = 2; // connect the push button to digital pin 2 | ||
int ledPin = 13; // connect the LED to pin 13 | int ledPin = 13; // connect the LED to pin 13 | ||
+ | int buttonState; | ||
void setup() { | void setup() { | ||
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void loop() { | void loop() { | ||
- | | + | buttonState = digitalRead(pushButtonPin); |
- | | + | |
if (buttonState == HIGH) // if the button is pushed | if (buttonState == HIGH) // if the button is pushed | ||
digitalWrite(ledPin, | digitalWrite(ledPin, | ||
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digitalWrite(ledPin, | digitalWrite(ledPin, | ||
- | // | + | // |
} | } | ||
</ | </ | ||
- | Notice the use of an '' | + | Notice the use of an '' |
A more compact version of the above that eliminates the if-else statement: | A more compact version of the above that eliminates the if-else statement: | ||
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int pushButtonPin = 2; // connect the push button to digital pin 2 | int pushButtonPin = 2; // connect the push button to digital pin 2 | ||
int ledPin = 13; // connect the LED to pin 13 | int ledPin = 13; // connect the LED to pin 13 | ||
+ | int buttonState; | ||
void setup() { | void setup() { | ||
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void loop() { | void loop() { | ||
- | | + | buttonState = digitalRead(pushButtonPin); |
digitalWrite(ledPin, | digitalWrite(ledPin, | ||
- | // | + | // |
} | } | ||
</ | </ | ||
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int pushButtonPin = 2; // connect the push button to digital pin 2 | int pushButtonPin = 2; // connect the push button to digital pin 2 | ||
int ledPin = 13; // connect the LED to pin 13 | int ledPin = 13; // connect the LED to pin 13 | ||
+ | int buttonState; | ||
void setup() { | void setup() { | ||
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void loop() { | void loop() { | ||
digitalWrite(ledPin, | digitalWrite(ledPin, | ||
- | // | + | // |
} | } | ||
</ | </ | ||
- | ==== Using internal | + | ==== With internal |
Using extenal resistors as part of switch state detection is so common that the microchip that is at the heart of the Arduino has built-in pullup resistors that can be turned on manually. Internal pullup resistors can be enabled with: | Using extenal resistors as part of switch state detection is so common that the microchip that is at the heart of the Arduino has built-in pullup resistors that can be turned on manually. Internal pullup resistors can be enabled with: | ||
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int pushButtonPin = 2; // connect the push button to digital pin 2 | int pushButtonPin = 2; // connect the push button to digital pin 2 | ||
int ledPin = 13; // connect the LED to pin 13 | int ledPin = 13; // connect the LED to pin 13 | ||
+ | int buttonState; | ||
void setup() { | void setup() { | ||
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void loop() { | void loop() { | ||
- | | + | buttonState = digitalRead(pushButtonPin); |
// set LED state accordingly | // set LED state accordingly | ||
- | // note the inverted | + | // becasue we are using pullup resistors, |
+ | // in other words, pressed produces LOW, un-pressed produces HIGH. | ||
if (buttonState == LOW) // if the button is pushed | if (buttonState == LOW) // if the button is pushed | ||
digitalWrite(ledPin, | digitalWrite(ledPin, | ||
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int pushButtonPin = 2; // connect the push button to digital pin 2 | int pushButtonPin = 2; // connect the push button to digital pin 2 | ||
int ledPin = 13; // connect the LED to pin 13 | int ledPin = 13; // connect the LED to pin 13 | ||
+ | int buttonState; | ||
void setup() { | void setup() { | ||
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void loop() { | void loop() { | ||
- | | + | buttonState = digitalRead(pushButtonPin); |
- | digitalWrite(ledPin, | + | |
+ | // set LED state accordingly | ||
+ | // becasue we are using pullup resistors, the logic is inverted; | ||
+ | // in other words, pressed produces LOW, un-pressed produces HIGH. | ||
+ | digitalWrite(ledPin, | ||
} | } | ||
</ | </ |
arduino/arduino_crash_course/basic_interaction.1351977174.txt.gz · Last modified: 2012/11/03 21:12 by mithat