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-rw-r--r--source/lang/api/attachinterrupt.rst36
1 files changed, 28 insertions, 8 deletions
diff --git a/source/lang/api/attachinterrupt.rst b/source/lang/api/attachinterrupt.rst
index 39902ac..58e4764 100644
--- a/source/lang/api/attachinterrupt.rst
+++ b/source/lang/api/attachinterrupt.rst
@@ -41,6 +41,12 @@ Library Documentation
.. doxygentypedef:: voidFuncPtr
+.. note::
+
+ You should set the :ref:`pin mode <lang-pinmode>` of your desired
+ pin to an input mode (e.g. ``INPUT``, ``INPUT_PULLUP``,
+ ``INPUT_PULLDOWN``).
+
Discussion
----------
@@ -50,31 +56,45 @@ Because the function will run in interrupt context, inside of it,
the function may be lost. You should declare as ``volatile`` any
global variables that you modify within the attached function.
-There are a few limits you should be aware of if you're using more
-than one interrupt at a time; the :ref:`External Interrupts
-<external-interrupts-exti-line>` page has more information.
+There are some limits you should be aware of if you're using
+``attachInterrupt()`` with more than one pin; the :ref:`External
+Interrupts <external-interrupts-exti-line>` page has more information.
Example
-------
- ::
+The following example blinks the LED any time pin 0 changes from
+``HIGH`` to ``LOW`` or vice versa. ::
volatile int state = LOW; // must declare volatile, since it's
// modified within the blink() handler
void setup() {
- pinMode(BOARD_LED_PIN, OUTPUT);
- attachInterrupt(0, blink, CHANGE);
+ pinMode(BOARD_LED_PIN, OUTPUT);
+ pinMode(0, INPUT);
+ attachInterrupt(0, blink, CHANGE);
}
void loop() {
- digitalWrite(BOARD_LED_PIN, state);
+ digitalWrite(BOARD_LED_PIN, state);
}
void blink() {
- state = !state;
+ if (state == HIGH) {
+ state = LOW;
+ } else { // state must be LOW
+ state = HIGH;
+ }
}
+In this example, the function ``blink()`` is the interrupt handler.
+Whenever the state on pin 0 changes, ``blink()`` gets called. It
+reacts to the change by changing the ``state`` variable to ``LOW`` if
+it is ``HIGH``, and to ``HIGH`` if it is ``LOW``. It then exits,
+letting the board get back to calling ``loop()``. Since ``loop()``
+sets the LED pin to whatever ``state`` is, changing the voltage on pin
+0 will toggle the LED.
+
Arduino Compatibility
---------------------