Changes to allow scanning and connections to work together. (#41)

Author: AdrianSoundy

README.md

@@ -20,14 +20,15 @@ This library is based on the Windows.Devices.Bluetooth UWP class library but sim
 The original .Net assembly depended on Windows.Storage.Streams for DataReader & DataWriter; this library has simplified inbuilt versions. 
 So references to IBuffer in .Net UWP examples should now use Buffer instead. 
 
-We have also added an extension to this assembly allowing extra services to be added with no restriction on type.
+We have also added an extension to this assembly allowing extra services to be added to ServiceProvider with no restriction on type.
 
 ## Firmware versions
 
 Bluetooth is currently only supported on ESP32 devices with following firmware.
 
 - ESP32_BLE_REV0
 - ESP32_BLE_REV3
+- M5Core2
 
 This restriction is due to IRAM memory space in the firmware image. 
 With revision 1 of ESP32 devices, the PSRAM implementation requires a large number of PSRAM fixes which greatly reduces the 
@@ -51,9 +52,10 @@ A number of Bluetooth LE samples are available in the [nanoFramework samples rep
 
 This implementation supports a cut down version of the Gatt Server and Gatt Client implementation.
 
-The device can either run as a Server, Client or Watcher, but not at the same time.  
+The device can either run as a Server or Client, but not at the same time.  
 For example if you start a Watcher to look for advertisements from Server devices you will not 
-be able to connect to those devices until the Watcher has been stopped.
+be able to connect to those devices until the Watcher has been stopped. But you can recieve data from connected 
+devices while Watcher is scanning.
 
 For more information see relevant sections: -
 
@@ -343,7 +345,7 @@ RSSI filter
 
 ## Creating a device and connecting to device.
 
-To communicate with a device a BluetoothLEDevice class needs to be created using the devices bluetooth address.
+To communicate with a device a BluetoothLEDevice class needs to be created using the devices bluetooth address and type.
 This can be the bluetooth address from the BluetoothLEAdvertisementWatcher event or using a hard coded address.
 
 In this case from the Watcher advertisement received event.
@@ -352,11 +354,12 @@ BluetoothLEDevice device = BluetoothLEDevice.FromBluetoothAddress(args.Bluetooth
 ```
 There are no specific connection methods but a connection will be made automatically when you query the device 
 for its services. The ConnectionStatusChanged event can used to detect a change in connection status and an attempt to 
-reconnect can be done by query the devices services again. Avoid doing this in the event it self as it can block other 
+reconnect can be done by a query to the devices services again. Avoid doing this in the event, as it can block other 
 events being fired during the connection.
 
-To go back to Watching for advertisements all connected devices need to be closed or disposed. This
-will put the stack in to an idle state so the Watching can be started.
+You can go back to Watching for advertisements with the restriction that you can't connect to newly found devcies until the Watching is stopped.
+You can still communication with connected devices while the Watcher is running. Best way is to collect all found devices in a table until Watcher is
+stopped then connect to all found devices. See [Central 2 sample](https://github.com/nanoframework/Samples/tree/main/samples/Bluetooth/Central2)
 
 The Close() method is not exposed in the desktop version but it has been implemented in this version 
 to give better control over the connection.

nanoFramework.Device.Bluetooth/BluetoothLEAdvertisementWatcher.cs

@@ -68,13 +68,8 @@ public BluetoothLEAdvertisementWatcher(BluetoothLEAdvertisementFilter advertisem
         /// </summary>
         public void Start()
         {
-            if (BluetoothNanoDevice.RunMode != BluetoothNanoDevice.Mode.NotRunning)
-            {
-                throw new InvalidOperationException("Wrong state");
-            }
-
-            // Set new run mode. 
-            BluetoothNanoDevice.RunMode = BluetoothNanoDevice.Mode.Scanning;
+            // Check and set mode
+            BluetoothNanoDevice.CheckMode(BluetoothNanoDevice.Mode.Client);
 
             _status = BluetoothLEAdvertisementWatcherStatus.Started;
             _scanResults = new Hashtable();
@@ -97,7 +92,7 @@ public void Stop()
 
             _status = BluetoothLEAdvertisementWatcherStatus.Stopped;
 
-            BluetoothNanoDevice.RunMode = BluetoothNanoDevice.Mode.NotRunning;
+            BluetoothLEDevice.IdleOnLastConnection();
         }
 
         /// <summary>

nanoFramework.Device.Bluetooth/BluetoothLEDevice.cs

@@ -72,6 +72,9 @@ private ushort GetConnectingHandle
 
         private GattCommunicationStatus ConnectDeviceIfNotConnected()
         {
+            // Check and set mode, throw exception if wrong state
+            BluetoothNanoDevice.CheckMode(BluetoothNanoDevice.Mode.Client);
+
             GattCommunicationStatus status = GattCommunicationStatus.Unreachable;
 
             if (_connectionStatus == BluetoothConnectionStatus.Disconnected)
@@ -399,6 +402,15 @@ internal GattWriteResult WriteAttributeValueWithResult(ushort attributeHandle, B
             return new GattWriteResult(status, (byte)result);
         }
 
+        internal static void IdleOnLastConnection()
+        {
+            if (GattServiceProvider._bluetoothEventManager.LeDeviceCount == 0)
+            {
+                // Reset run mode
+                BluetoothNanoDevice.RunMode = BluetoothNanoDevice.Mode.NotRunning;
+            }
+        }
+
         /// <summary>
         /// Central event handler from native code.
         /// </summary>
@@ -435,12 +447,9 @@ internal void OnEvent(BluetoothEventCentral btEvent)
                     // Remove  device from event handler
                     GattServiceProvider._bluetoothEventManager.RemoveLeDevice(this);
 
-                    if (GattServiceProvider._bluetoothEventManager.LeDeviceCount == 0)
-                    {
-                        // Last active device, close down stack
-                        //Debug.WriteLine("# Last active LE device");
-                        NativeDispose(_connectionHandle);
-                    }
+                    NativeDispose(_connectionHandle);
+
+                    IdleOnLastConnection();
 
                     break;
 
@@ -596,6 +605,7 @@ protected virtual void Dispose(bool disposing)
                 // Make sure we are removed from event listener
                 GattServiceProvider._bluetoothEventManager.RemoveLeDevice(this);
 
+                IdleOnLastConnection();
             }
         }
 

nanoFramework.Device.Bluetooth/BluetoothNanoDevice.cs

@@ -9,13 +9,14 @@
 //  As we can't run both Server or Central/Client at same time
 //
 
+using System;
 using System.Runtime.CompilerServices;
 
 namespace nanoFramework.Device.Bluetooth
 {
     internal static class BluetoothNanoDevice
     {
-        internal enum Mode { NotRunning, Server, Scanning, Central };
+        internal enum Mode { NotRunning, Server, Client };
 
         [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
         private static string _deviceName = "";
@@ -30,6 +31,18 @@ static BluetoothNanoDevice()
 
         internal static string DeviceName { get => _deviceName; set => _deviceName = value; }
 
+        internal static void CheckMode(Mode expectedMode)
+        {
+            if (BluetoothNanoDevice.RunMode != expectedMode &&
+                BluetoothNanoDevice.RunMode != Mode.NotRunning)
+            {
+                throw new InvalidOperationException("Wrong state");
+            }
+
+            // Set new run mode. 
+            BluetoothNanoDevice.RunMode = expectedMode;
+        }
+
         /// <summary>
         /// Get/Set the current mode of the device.
         /// </summary>

nanoFramework.Device.Bluetooth/GenericAttributeProfile/GattServiceProvider.cs

@@ -95,16 +95,11 @@ public void StartAdvertising()
         /// <param name="parameters">The advertising parameters.</param>
         public void StartAdvertising(GattServiceProviderAdvertisingParameters parameters)
         {
-            if (BluetoothNanoDevice.RunMode != BluetoothNanoDevice.Mode.NotRunning)
-            {
-                throw new InvalidOperationException("Wrong state");
-            }
+            // Check and switch to server mode
+            BluetoothNanoDevice.CheckMode(BluetoothNanoDevice.Mode.Server);
 
             BluetoothNanoDevice.DeviceName = parameters.DeviceName;
 
-            // Switch to client/server mode
-            BluetoothNanoDevice.RunMode = BluetoothNanoDevice.Mode.Server;
-
             // Save parameters
             _isConnectable = parameters.IsConnectable;
             _isDiscoverable = parameters.IsDiscoverable;

nanoFramework.Device.Bluetooth/Properties/AssemblyInfo.cs

@@ -17,7 +17,7 @@
 
 ////////////////////////////////////////////////////////////////
 // update this whenever the native assembly signature changes //
-[assembly: AssemblyNativeVersion("100.0.1.0")]
+[assembly: AssemblyNativeVersion("100.0.2.0")]
 ////////////////////////////////////////////////////////////////