interrupts (1)

7/24/2019 Interrupts (1)

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INTERRUPTSDEFINITION

USAGE

SYNTAX

SIDE EFFECTS


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DEFINITION An interrupt (in our context) is a perturbat

caused to a running program, and handled

automatically.

This perturbation causes the program to st

handle the interrupt, and then resume.

Handling the interrupt is done through a fu

called Interrupt Service Routine (ISR).


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USAGE To avoid always checking the input of

sensors at every iteration, you can use

interrupt triggered whenever the sensor

active.

The interrupt can start on:

rising edge, falling edge, change, low

high (not available in UNO).


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USAGE You SHOULD write a specific function

be called when the interrupt is triggere

This function SHOULD be VOID with

NO ARGUMENTS. For our programs, we will trigger the

interrupt on the rising edge.


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USAGE The interrupt input should be defined i

program.

By default, pins 2 & 3 are interrupt pin

Arduino UNO, but use the functiondigitalPinToInterrupt(pin) with pin = 2


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SYNTAX When c

goBackprogram

anywhe

main.

We may

declare

input.


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SIDE EFFECTS The function delay wont work in ISR

The function millis wont work in ISR

The function micros works correctly fo

1-2ms and then misbehaves. The function delayMicroseconds work

fin in ISR.


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SIDE EFFECTS Only one ISR runs at a time

If many interrupts happen, ISRs will exec

depending on hardware priority.

If too many interrupts happen at once, som

may be lost.

Interrupts dont interrupt ISRs.

ISRs should be short.


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SIDE EFFECTS If you change a variable inside an ISR,

and you want to keep it changed, you

should declare it as volatile.

If you need to execute some statements

without interruption, use noInterrupts

function, and remember to re-enable th

using interrupts() function.


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SIDE EFFECTS If a

volati

chang

will d

after t

ends.


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interrupts (1)

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