add Events examples

Author: maciejbocianski

APIs_RTOS/EventQueue_ex_2/README.md

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+# EventQueue example
+
+This example shows how to queue functions.
+

APIs_RTOS/EventQueue_ex_2/main.cpp

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+#include "mbed_events.h"
+#include <stdio.h>
+
+int main()
+{
+    // creates a queue with the default size
+    EventQueue queue;
+
+    // events are simple callbacks
+    queue.call(printf, "called immediately\n");
+    queue.call_in(2000, printf, "called in 2 seconds\n");
+    queue.call_every(1000, printf, "called every 1 seconds\n");
+
+    // events are executed by the dispatch method
+    queue.dispatch();
+}

APIs_RTOS/EventQueue_ex_3/README.md

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+# EventQueue example
+
+This example shows how to chain events from more than one EventQueue.
+

APIs_RTOS/EventQueue_ex_3/main.cpp

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+#include "mbed_events.h"
+#include <stdio.h>
+
+/**
+Event queues easily align with module boundaries, where internal state can be
+implicitly synchronized through event dispatch. Multiple modules can use
+independent event queues, but still be composed through the EventQueue::chain function.
+**/
+
+int main()
+{
+    // Create some event queues with pending events
+    EventQueue a;
+    a.call(printf, "hello from a!\n");
+
+    EventQueue b;
+    b.call(printf, "hello from b!\n");
+
+    EventQueue c;
+    c.call(printf, "hello from c!\n");
+
+    // Chain c and b onto a's event queue. Both c and b will be dispatched
+    // in the context of a's dispatch function.
+    c.chain(&a);
+    b.chain(&a);
+
+    // Dispatching a will in turn dispatch b and c, printing hello from
+    // all three queues
+    a.dispatch();
+}

APIs_RTOS/Shared_Events_1/README.md

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+# Shared event example
+
+Instead of creating special thread user can use shared event queue and dispatch the global event queue from main thread.
+

APIs_RTOS/Shared_Events_1/main.cpp

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+#include "mbed.h"
+#include "mbed_events.h"
+
+DigitalOut led1(LED1);
+InterruptIn sw(SW2);
+
+void rise_handler(void)
+{
+    // Toggle LED
+    led1 = !led1;
+}
+
+void fall_handler(void)
+{
+    printf("fall_handler in context %p\r\n", ThisThread::get_id());
+    // Toggle LED
+    led1 = !led1;
+}
+
+int main()
+{
+    // Request the shared queue
+    EventQueue *queue = mbed_event_queue();
+    printf("Starting in context %p\r\n", ThisThread::get_id());
+    // The 'rise' handler will execute in IRQ context
+    sw.rise(rise_handler);
+    // The 'fall' handler will execute in the context of the shared queue thread
+    sw.fall(queue->event(fall_handler));
+}

APIs_RTOS/Shared_Events_2/README.md

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+# Shared event example
+
+Instead of creating special thread user can use shared event queue i.e. sharing it with other system components and saving RAM. As the event queue is shared, you should limit the execution time of your event functions to avoid delaying other users’ events excessively. 
+

APIs_RTOS/Shared_Events_2/main.cpp

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+#include "mbed.h"
+#include "mbed_events.h"
+
+DigitalOut led1(LED1);
+InterruptIn sw(SW2);
+
+void rise_handler(void)
+{
+    // Toggle LED
+    led1 = !led1;
+}
+
+void fall_handler(void)
+{
+    printf("fall_handler in context %p\r\n", ThisThread::get_id());
+    // Toggle LED
+    led1 = !led1;
+}
+
+int main()
+{
+    // Request the shared queue
+    EventQueue *queue = mbed_event_queue();
+    printf("Starting in context %p\r\n", ThisThread::get_id());
+    // The 'rise' handler will execute in IRQ context
+    sw.rise(rise_handler);
+    // The 'fall' handler will execute in the context of the shared queue (actually the main thread)
+    sw.fall(queue->event(fall_handler));
+    // Setup complete, so we now dispatch the shared queue from main
+    queue->dispatch_forever();
+}

APIs_RTOS/Shared_Events_2/mbed_app.json

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+{
+    "target_overrides": {
+        "*": {
+            "events.shared-dispatch-from-application": true
+        }
+     }
+}

APIs_RTOS/mbed-os-example-events/README.md

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+# EventQueue example
+
+This example shows how to instantiate, configure and post events.
+

APIs_RTOS/mbed-os-example-events/main.cpp

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+#include "mbed.h"
+
+// Creates an event bound to the specified event queue
+EventQueue queue;
+void handler(int count);
+Event<void(int)> event(&queue, handler);
+
+void handler(int count)
+{
+    printf("Event = %d \n", count);
+    return;
+}
+
+void post_events(void)
+{
+
+    // Events can be posted multiple times and enqueue gracefully until
+    // the dispatch function is called.
+    event.post(1);
+    event.post(2);
+    event.post(3);
+}
+
+int main()
+{
+
+    Thread event_thread;
+
+    // The event can be manually configured for special timing requirements
+    // specified in milliseconds
+    event.delay(100);       // Starting delay - 100 msec
+    event.period(200);      // Delay between each evet - 200msec
+
+    event_thread.start(callback(post_events));
+
+    // Posted events are dispatched in the context of the queue's
+    // dispatch function
+    queue.dispatch(400);        // Dispatch time - 400msec
+    // 400 msec - Only 2 set of events will be dispatched as period is 200 msec
+
+    event_thread.join();
+}