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Diffstat (limited to 'source/arduino/attachinterrupt.rst')
| -rw-r--r-- | source/arduino/attachinterrupt.rst | 66 |
1 files changed, 36 insertions, 30 deletions
diff --git a/source/arduino/attachinterrupt.rst b/source/arduino/attachinterrupt.rst index 189141b..cb11327 100644 --- a/source/arduino/attachinterrupt.rst +++ b/source/arduino/attachinterrupt.rst @@ -2,8 +2,18 @@ .. _arduino-attachinterrupt: -attachInterrupt(interrupt, function, mode) -========================================== +attachInterrupt() +================= + +Used to specify a function to call when an external interrupt (like an +GPIO changing from LOW to HIGH, a button getting pressed, etc.) +occurs. + +.. contents:: Contents + :local: + +Library Documentation +--------------------- .. doxygenfunction:: attachInterrupt @@ -14,17 +24,15 @@ attachInterrupt(interrupt, function, mode) Discussion ---------- -Specifies a function to call when an external interrupt occurs. -Replaces any previous function that was attached to the interrupt. -For more information on external interrupts on the Maple +Because the function will run in interrupt context, inside of it, +:ref:`arduino-delay` won't work, and the value returned by +:ref:`arduino-millis` will not increment. Serial data received while +in the function may be lost. You should declare as ``volatile`` any +global variables that you modify within the attached function. -Note ----- - -Inside the attached function, delay() won't work, and the value -returned by millis() will not increment. Serial data received while in -the function may be lost. You should declare as volatile any variables -that you modify within the attached function. +There are a few constraints you should be aware of if you're using +more than one interrupt at a time; the :ref:`external-interrupts` page +has the details. Using Interrupts @@ -33,8 +41,7 @@ Using Interrupts Interrupts are useful for making things happen automatically in microcontroller programs, and can help solve timing problems. A good task for using an interrupt might be reading a rotary encoder, -monitoring user input. - +or monitoring user input. If you wanted to insure that a program always caught the pulses @@ -49,45 +56,44 @@ situations, using an interrupt can free the microcontroller to get some other work done while not missing the doorbell. - Example ------- :: int maple_led_pin = 13; - volatile int state = LOW; - - void setup() - { + volatile int state = LOW; // must declare volatile, since it's + // modified within the blink handler + + void setup() { pinMode(maple_led_pin, OUTPUT); attachInterrupt(0, blink, CHANGE); } - - void loop() - { + + void loop() { digitalWrite(maple_led_pin, state); } - - void blink() - { + + void blink() { state = !state; } -Arduino Compatibility Note --------------------------- +Arduino Compatibility +--------------------- Most Arduino boards have two external interrupts: numbers 0 (on digital pin 2) and 1 (on digital pin 3). The Arduino Mega has an additional four: numbers 2 (pin 21), 3 (pin 20), 4 (pin 19), and 5 -(pin 18). +(pin 18). On the Maple, you don't have to remember which interrupt +number goes with which pin -- just tell ``attachInterrupt()`` the pin +you want. See also -------- -- `detachInterrupt <http://arduino.cc/en/Reference/DetachInterrupt>`_ - +- :ref:`detachInterrupt <arduino-detachinterrupt>` +- :ref:`external-interrupts` |