Merge pull request ARMmbed#64 from pan-/ble_button_instructions

Improve BLE_Button documentation.

Author: pan-

BLE_Button/readme.md

@@ -4,7 +4,7 @@ The template covers:
 
 1. Setting up advertising and connection modes.
 
-1. Creating an input characteristic: read-only, boolean, with notifications. 
+1. Creating an input characteristic: read-only, boolean, with notifications.
 
 1. Constructing a service class and adding it to the BLE stack.
 
@@ -32,7 +32,9 @@ Building instructions for all samples are in the [main readme](https://github.co
 
 1. Build the application and install it on your board as explained in the building instructions.
 1. Open the BLE scanner on your phone.
-1. Find your device.
-1. Press the button on your board. 
-1. The characteristic is automatically updated on every press and release, and the BLE scanner shows its value changes. 
-
+1. Find your device, it should appear with the name `Button` in the scanner.
+1. Establish a connection with the device.
+1. Discover the services and the characteristics on the device. The *Button service* has the UUID `0xA000` and includes the *Button state characteristic* which has the UUID `0xA001`.
+1. Register for the notifications sent by the button state characteristic then the scanner will automatically receive a notification containing the new state of the button every time the state of the button changes.
+1. Pressing Button 1 on your board updates the state of the button and sends a notification to the scanner. The new state of the button characteristic value should be equal to 0x01.
+1. Releasing Button 1 on your board updates the state of the button and sends a notification to the scanner. The new state of the button characteristic value should be equal to 0x00.