Improved button support

Modify the main.cpp to understand the new "abstract" buttons in mbed OS.
Prevoius buttons were applicable only to K64F, but since mbed OS has
BUTTON1 and BUTTON2, you can check for those in a board independent manner.

Add instructions how to figure out which button is which one.

Author: Janne Kiiskilä

README.md

@@ -367,28 +367,40 @@ Registered object succesfully!
 
 <span class="notes">**Note:** Device name is the endpoint name you will need later on when [testing the application](https://github.com/ARMmbed/mbed-os-example-client#testing-the-application).</span>
 
-When you press the **SW2** button on your board you should see messages about the value changes:
+When you press the **BUTTON1** button on your board you should see messages about the value changes:
 
 ```
 handle_button_click, new value of counter is 1
 ```
+## Which button is BUTTON1 or BUTTON2?
 
+The abstract button definitions are not printed on the boards. The easiest way to find out which button is which is to grep the code. Example below finds the `BUTTON1` for K64F.
+
+```bash
+<shell: mbed-os-example-client/> cd mbed-os
+<shell: mbed-os-example-client/mbed-os>$ git grep BUTTON1 |grep -i K64F
+targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/TARGET_FRDM/PinNames.h:    BUTTON1 = SW2,
+```
+
+I.e. we can deduce that BUTTON1 is the button labeled SW2 in the actual physical board.
+
+ 
 ## Testing the application
 
 1. Flash the application.
 2. Verify that the registration succeeded. You should see `Registered object successfully!` printed to the serial port.
 3. On mbed Device Connector, go to [My devices > Connected devices](https://connector.mbed.com/#endpoints). Your device should be listed here.
-4. Press the **SW2** button on the device a number of times (make a note of how many times you did that).
+4. Press the **BUTTON1** button on the device a number of times (make a note of how many times you did that).
 5. Go to [Device Connector > API Console](https://connector.mbed.com/#console).
 6. Click the **Endpoint directory lookups** drop down menu.
     ![](/docs/img/ep_lookup.PNG) 
 7. In the menu, click **GET** next to **Endpoint's resource representation**. Select your _endpoint_ and _resource-path_. For example, the _endpoint_ is the identifier of your endpoint that can be found in the `security.h` file as `MBED_ENDPOINT_NAME`. Select `3200/0/5501`as a resource path and click **TEST API**. 
-8. The number of times you pressed **SW2** is shown.
-9. Press the **SW3** button to unregister from mbed Device Connector. You should see `Unregistered Object Successfully` printed to the serial port and the LED starts blinking. This will also stop your application. Press the **Reset** button to run the program again.
+8. The number of times you pressed **BUTTON1** is shown.
+9. Press the **BUTTON2** button to unregister from mbed Device Connector. You should see `Unregistered Object Successfully` printed to the serial port and the LED starts blinking. This will also stop your application. Press the **Reset** button to run the program again.
 
-<span class="notes">**Note:** On non-K64F boards, there is no unregistration functionality and button presses are simulated through timer ticks incrementing every 15 seconds.</span>
+<span class="notes">**Note:** On boards without BUTTON2 there is no unregistration functionality. Boards without buttons the button presses are simulated through timer ticks incrementing every 15 seconds. Please note the actual printout on the board for the BUTTON1 and BUTTON2 changes a lot - you need map that out from the mbed OS board files.</span>
 
-![SW2 pressed five times, as shown by the API Console](clicks.png)
+![BUTTON1 pressed five times, as shown by the API Console](clicks.png)
 
 <span class="tips">**Tip:** If you get an error, for example `Server Response: 410 (Gone)`, clear your browser's cache, log out, and log back in.</span>
 
@@ -398,14 +410,18 @@ handle_button_click, new value of counter is 1
 
 The application exposes three [resources](https://docs.mbed.com/docs/mbed-device-connector-web-interfaces/en/latest/#the-mbed-device-connector-data-model):
 
-1. `3200/0/5501`. Number of presses of **SW2** (GET).
+1. `3200/0/5501`. Number of presses of **BUTTON1** (GET).
 2. `3201/0/5850`. Blink function, blinks **LED1** when executed (POST).
 3. `3201/0/5853`. Blink pattern, used by the blink function to determine how to blink. In the format of `1000:500:1000:500:1000:500` (PUT).
 
 To learn how to get notifications when resource 1 changes, or how to use resources 2 and 3, read the [mbed Device Connector Quick Start](https://github.com/ARMmbed/mbed-connector-api-node-quickstart).
 
 ## Known issues
 
+### mbed OS 5.5
+
+* [UBLOX_EVK_ODIN_W2]: BUTTON1 and BUTTON2 definitions are missing from board file.
+
 ### mbed OS 5.4
 
 * [UBLOX_EVK_ODIN_W2]: This example is not compiling with IAR. See [#194](https://github.com/ARMmbed/mbed-os-example-client/issues/194)

main.cpp

@@ -66,18 +66,22 @@ struct MbedClientDevice device = {
 MbedClient mbed_client(device);
 
 
-// In case of K64F board , there is button resource available
-// to change resource value and unregister
-#ifdef TARGET_K64F
+// If board has a button_1, use it to update the counter.
+#ifdef BUTTON1
 // Set up Hardware interrupt button.
-InterruptIn obs_button(SW2);
-InterruptIn unreg_button(SW3);
-#else
+InterruptIn obs_button(BUTTON1);
+#else // BUTTON1
 //In non K64F boards , set up a timer to simulate updating resource,
 // there is no functionality to unregister.
 Ticker timer;
 #endif
 
+// If the board has a 2nd button - hook the unregistration to that.
+#ifdef BUTTON2
+InterruptIn unreg_button(BUTTON2);
+#endif // BUTTON2
+
+
 /*
  * Arguments for running "blink" in it's own thread.
  */
@@ -242,11 +246,11 @@ class ButtonResource {
 
             // up counter
             counter++;
-    #ifdef TARGET_K64F
+    #ifdef BUTTON1
             printf("handle_button_click, new value of counter is %d\n", counter);
     #else
             printf("simulate button_click, new value of counter is %d\n", counter);
-    #endif
+    #endif // BUTTON1
             // serialize the value of counter as a string, and tell connector
             char buffer[20];
             int size = sprintf(buffer,"%d",counter);
@@ -373,18 +377,20 @@ Add MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES and MBEDTLS_TEST_NULL_ENTROPY in mbed_app
     LedResource led_resource;
     BigPayloadResource big_payload_resource;
 
-#ifdef TARGET_K64F
-    // On press of SW3 button on K64F board, example application
+#ifdef BUTTON2
+    // On press 2nd button (boards that have it), example application
     // will call unregister API towards mbed Device Connector
     //unreg_button.fall(&mbed_client,&MbedClient::test_unregister);
     unreg_button.fall(&unregister);
+#endif // BUTTON2
 
-    // Observation Button (SW2) press will send update of endpoint resource values to connector
+#ifdef BUTTON1
+    // 1st button - observation button press will send update of endpoint resource values to connector
     obs_button.fall(&button_clicked);
 #else
     // Send update of endpoint resource values to connector every 15 seconds periodically
     timer.attach(&button_clicked, 15.0);
-#endif
+#endif // BUTTON1
 
     // Create endpoint interface to manage register and unregister
     mbed_client.create_interface(MBED_SERVER_ADDRESS, network);