Merge branch 'callback_interrupt_handlers'

1 files changed, 87 insertions, 0 deletions

diff --git a/examples/exti-interrupt-callback.cpp b/examples/exti-interrupt-callback.cpp
new file mode 100644
index 0000000..c87c064
--- /dev/null
+++ b/examples/exti-interrupt-callback.cpp
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+// Toggles the built-in LED when the built in button
+// on the Maple is pushed in. This uses the attachInterrupt function to
+// setup the interrupt handler for the button being pressed.
+//
+// This is similar to the exti-interrupt example, but shows the use of a class
+// method to handle interrupts.
+//
+// More about attachInterrupt:
+// http://leaflabs.com/docs/lang/api/attachinterrupt.html
+//
+
+
+#include <wirish/wirish.h>
+
+class MyAwesomeClass {
+public:
+    // Setup the interrupt handler
+    void initialize() {
+        // LED is off by default
+        this->isLEDOn = false;
+
+        // Attach interrupt to class method handler
+        attachInterrupt(BOARD_BUTTON_PIN, buttonInterruptHandler, this, RISING);
+    }
+
+private:
+
+    bool isLEDOn;
+
+    // Static event handler takes a void * argument that was originally
+    // passed to the attachInterrupt call. If the argument in question is an
+    // instance of the class (MyAwesomeClass in this case), the static function
+    // get access to that instance's data (even private data).
+    //
+    // In other words, this setup allows the Maple to have class method
+    // interrupt handlers (albeit with a work around).
+    //
+    // However, as you might imagine, this argument can be anything (if you
+    // don't need instance data access).
+    //
+    static void buttonInterruptHandler(void *arg) {
+        // Cast the "generic" void argument to the class instance.
+        MyAwesomeClass *instance = (MyAwesomeClass *)arg;
+
+        // Accessing private instance data
+        instance->isLEDOn = !(instance->isLEDOn);
+
+        // Set LED
+        digitalWrite(BOARD_LED_PIN, instance->isLEDOn);
+
+        // Delay slightly for switch de-bouncing
+        delay(20);
+    }
+};
+
+MyAwesomeClass myClass;
+
+// Setup pin modes and the interrupt handler class
+void setup() {
+    pinMode(BOARD_BUTTON_PIN, INPUT);
+    pinMode(BOARD_LED_PIN, OUTPUT);
+
+    // The initialize method sets up the event handler to the private method
+    // in MyAwesomeClass. There is however, nothing stopping you from setting
+    // up event handlers which are public methods in classes.
+    myClass.initialize();
+}
+
+// Loop. Does nothing in this example.
+void loop() {
+
+}
+
+// Force init to be called *first*, i.e. before static object allocation.
+// Otherwise, statically allocated objects that need libmaple may fail.
+__attribute__((constructor)) void premain() {
+    init();
+}
+
+int main(void) {
+    setup();
+
+    while (true) {
+        loop();
+    }
+    return 0;
+}