Document Pi Pico W BLE support

doxygen/Doxyfile

@@ -1012,6 +1012,7 @@ RECURSIVE              = YES
 
 EXCLUDE                = ../src/AH/STL \
                          ../src/MIDI_Interfaces/BLEMIDI/ESP32/README.md \
+                         ../src/MIDI_Interfaces/BLEMIDI/ESP32-NimBLE/README.md \
                          ../src/Submodules/Encoder/README.md
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or

doxygen/pages/MIDI-over-BLE.md

@@ -24,7 +24,7 @@ backend for the particular board.
 | Arduino MKR 1010 WiFi               | @ref ArduinoBLEBackend     |                          |
 | Arduino UNO R4 WiFi                 | @ref ArduinoBLEBackend     |                          |
 | Arduino GIGA R1 WiFi                | @ref ArduinoBLEBackend     |                          |
-| Raspberry Pi Pico W (RP2040)        | Not yet supported          |                          |
+| Raspberry Pi Pico W (RP2040)        | @ref BTstackBackgroundBackend |                       |
 | ESP32                               | @ref ESP32BluedroidBackend | @ref ESP32NimBLEBackend  |
 | ESP32-S3                            | @ref ESP32BluedroidBackend | @ref ESP32NimBLEBackend  |
 | ESP32-C3, ESP32-C6, ESP32-H2        | @ref ESP32BluedroidBackend | @ref ESP32NimBLEBackend  |
@@ -67,3 +67,16 @@ library in order to use this backend.
 
 Defining @ref CS_USE_NIMBLE before including Control Surface changes the default
 backend for ESP32 to the @ref ESP32NimBLEBackend.
+
+### BTstackBackgroundBackend
+
+This backend uses the [BTstack](https://github.com/bluekitchen/btstack) stack
+that ships with the [pico-sdk](https://github.com/raspberrypi/pico-sdk).
+
+All Bluetooth events are handled asynchronously (using the background
+[`async_context`](https://www.raspberrypi.com/documentation/pico-sdk/networking.html#ga092b97e879be5b9aa9121abda23e1337)).
+Currently, buffering outgoing MIDI messages still requires polling, although
+this could be replaced by a BTstack timer in the future.
+
+To use the @ref BluetoothMIDI_Interface on the Pico W, you have to enable the
+Bluetooth stack in the _Tools > IP/Bluetooth Stack_ menu in the IDE: <https://arduino-pico.readthedocs.io/en/latest/bluetooth.html#enabling-bluetooth>

doxygen/pages/MIDI-over-USB.md

@@ -29,7 +29,7 @@ There are some differences in MIDI over USB implementation between different typ
 | Teensy LC, 3.0, 3.1, 3.2, 3.5, 4.0  | ✅  | ✅  | ❓  | ❌  |
 | Teensy 3.6, 4.1                     | ✅  | ✅  | ✅  | ❌  |
 | Raspberry Pi Pico (RP2040)          | ✅  | ✅  | ❓  | ❌  |
-| Raspberry Pi Pico W (RP2040)        | ✅  | ✅  | ❓  | ❓  |
+| Raspberry Pi Pico W (RP2040)        | ✅  | ✅  | ❓  | ✅  |
 | ESP8266                             | ✅  | ❌  | ❌  | ❌  |
 | ESP32                               | ✅  | ❌  | ❌  | ✅  |
 | ESP32-S2                            | ✅  | 🔼  | ❓  | ❌  |

examples/3. MIDI Interfaces/BLEMIDI-Adapter/BLEMIDI-Adapter.ino

@@ -1,7 +1,18 @@
 /**
  * Turns an Arduino into a Bluetooth Low Energy (BLE) to 5-pin DIN MIDI adapter.
  * 
- * @boards  Nano 33 IoT, Nano 33 BLE, ESP32, ESP32-S3
+ * @boards  Nano 33 IoT, Nano 33 BLE, ESP32, ESP32-S3, Pi Pico W
+ *
+ * Configuration
+ * -------------
+ *
+ * - If you're using a Pi Pico W, you'll have to enable the Bluetooth stack
+ *     from the _Tools > IP/Bluetooth Stack_ menu in the IDE.
+ * - If you're using an ESP32, you can optionally switch to the NimBLE backend
+ *     by installing the [h2zero/NimBLE-Arduino](https://github.com/h2zero/NimBLE-Arduino)
+ *     library, and adding `#define CS_USE_NIMBLE` at the top of this sketch.
+ * - If you're not using a Pico or an ESP32, you'll have to install the
+ *     [ArduinoBLE](https://github.com/arduino-libraries/ArduinoBLE) library.
  *
  * Connections
  * -----------

examples/examples.dox

@@ -1692,7 +1692,18 @@
  *
  * Turns an Arduino into a Bluetooth Low Energy (BLE) to 5-pin DIN MIDI adapter.
  * 
- * @boards  Nano 33 IoT, Nano 33 BLE, ESP32, ESP32-S3
+ * @boards  Nano 33 IoT, Nano 33 BLE, ESP32, ESP32-S3, Pi Pico W
+ *
+ * Configuration
+ * -------------
+ *
+ * - If you're using a Pi Pico W, you'll have to enable the Bluetooth stack
+ *     from the _Tools > IP/Bluetooth Stack_ menu in the IDE.
+ * - If you're using an ESP32, you can optionally switch to the NimBLE backend
+ *     by installing the [h2zero/NimBLE-Arduino](https://github.com/h2zero/NimBLE-Arduino)
+ *     library, and adding `#define CS_USE_NIMBLE` at the top of this sketch.
+ * - If you're not using a Pico or an ESP32, you'll have to install the
+ *     [ArduinoBLE](https://github.com/arduino-libraries/ArduinoBLE) library.
  *
  * Connections
  * -----------

test/examples-board-fqbns.yaml

@@ -13,4 +13,5 @@ nano 33 iot: arduino:samd:nano_33_iot
 nano 33 ble: arduino:mbed_nano:nano33ble
 nano every: arduino:megaavr:nona4809:mode=off
 pi pico: arduino:mbed_rp2040:pico
+pi pico w: rp2040:rp2040:rpipicow:ipbtstack=ipv4btcble
 uno r4: arduino:renesas_uno:minima