Add README to bluetooth-services; Move display scroll so services are created first

source/examples/bluetooth-services/README.md

@@ -0,0 +1,41 @@
+# Bluetooth Services
+
+The Bluetooth services project aims to provide a sample program that creates all of the services in micro:bit profile.
+
+However, with the current Bluetooth stack the micro:bit will throw an `020` [out of memory error](https://microbit.org/guide/hardware/error-codes/) if all services are created simultaneously.
+
+To avoid this both the DFU and Event Service are disabled in the project's `config.json`. If you wish to test these out, the easiest way to free enough memory is to disable the Magnetometer Service.
+
+---
+
+Enable DFU and Event Service in `config.json`
+```
+{
+    "microbit-dal": {
+        "bluetooth": {
+            "enabled": 1,
+            "pairing_mode": 1,
+            "private_addressing": 0,
+            "open": 0,
+            "whitelist": 1,
+            "advertising_timeout": 0,
+            "tx_power": 0,
+            "dfu_service": 1,
+            "event_service": 1,
+            "device_info_service": 1,
+            "security_level": "SECURITY_MODE_ENCRYPTION_NO_MITM"
+        },
+        "gatt_table_size": "0x700"
+    }
+}
+```
+
+Disable the Magnetometer Service by commenting it out:
+```
+    new MicroBitAccelerometerService(*uBit.ble, uBit.accelerometer);
+    new MicroBitButtonService(*uBit.ble);
+    new MicroBitIOPinService(*uBit.ble, uBit.io);
+    new MicroBitLEDService(*uBit.ble, uBit.display);
+    // new MicroBitMagnetometerService(*uBit.ble, uBit.compass);
+    new MicroBitTemperatureService(*uBit.ble, uBit.thermometer);
+```

source/examples/bluetooth-services/main.cpp

@@ -27,15 +27,27 @@ DEALINGS IN THE SOFTWARE.
 
 MicroBit uBit;
 
-// we use events abd the 'connected' variable to keep track of the status of the Bluetooth connection
-void onConnected(MicroBitEvent)
-{
-    uBit.display.print("C");
-}
+#define NONE 0
+#define CONNECTED 'C'
+#define DISCONNECTED 'D'
+
+uint8_t lastEvent = NONE;
 
-void onDisconnected(MicroBitEvent)
+// An event handler for BLE connection events
+// We keep track of the last event to show the correct character after the initial info has been displayed
+void onBLEEvent(MicroBitEvent evt)
 {
-    uBit.display.print("D");
+    // Determine if the event originates from a connect or disconnect
+    switch(evt.value) {
+        case MICROBIT_BLE_EVT_CONNECTED:
+            lastEvent = CONNECTED;
+            break;
+        case MICROBIT_BLE_EVT_DISCONNECTED:
+            lastEvent = DISCONNECTED;
+            break;
+    }
+
+    uBit.display.printChar(lastEvent);
 }
 
 int main()
@@ -84,12 +96,7 @@ int main()
     // TX Power Level
     // 0-7 taken from tx_power in config.json
 
-
-    // Services/Pairing Config/Power Level
-    uBit.display.scroll("BLE ABDILMT/P/0");
-
-    uBit.messageBus.listen(MICROBIT_ID_BLE, MICROBIT_BLE_EVT_CONNECTED, onConnected);
-    uBit.messageBus.listen(MICROBIT_ID_BLE, MICROBIT_BLE_EVT_DISCONNECTED, onDisconnected);
+    uBit.messageBus.listen(MICROBIT_ID_BLE, MICROBIT_EVT_ANY, onBLEEvent);
 
     new MicroBitAccelerometerService(*uBit.ble, uBit.accelerometer);
     new MicroBitButtonService(*uBit.ble);
@@ -98,6 +105,12 @@ int main()
     new MicroBitMagnetometerService(*uBit.ble, uBit.compass);
     new MicroBitTemperatureService(*uBit.ble, uBit.thermometer);
 
+    // Services/Pairing Config/Power Level
+    uBit.display.scroll("BLE ABDILMT/P/0");
+
+    if(lastEvent)
+        uBit.display.printChar(lastEvent);
+
     // If main exits, there may still be other fibers running or registered event handlers etc.
     // Simply release this fiber, which will mean we enter the scheduler. Worse case, we then
     // sit in the idle task forever, in a power efficient sleep.