examples/bluetooth: Add basic BLE peripheral examples.

Consisting of:
- ble_advertising.py -- helper to generate advertising payload.
- ble_temperature.py -- simple temperature device.
- ble_uart_periperhal.py -- BLE UART wrapper.
- ble_uart_repl.py -- dupterm-compatible uart.

examples/bluetooth/ble_uart_peripheral.py

@@ -0,0 +1,78 @@
+# This example demonstrates a peripheral implementing the Nordic UART Service (NUS).
+
+import bluetooth
+from ble_advertising import advertising_payload
+
+from micropython import const
+_IRQ_CENTRAL_CONNECT                 = const(1 << 0)
+_IRQ_CENTRAL_DISCONNECT              = const(1 << 1)
+_IRQ_GATTS_WRITE                     = const(1 << 2)
+
+_UART_UUID = bluetooth.UUID('6E400001-B5A3-F393-E0A9-E50E24DCCA9E')
+_UART_TX = (bluetooth.UUID('6E400003-B5A3-F393-E0A9-E50E24DCCA9E'), bluetooth.FLAG_NOTIFY,)
+_UART_RX = (bluetooth.UUID('6E400002-B5A3-F393-E0A9-E50E24DCCA9E'), bluetooth.FLAG_WRITE,)
+_UART_SERVICE = (_UART_UUID, (_UART_TX, _UART_RX,),)
+
+# org.bluetooth.characteristic.gap.appearance.xml
+_ADV_APPEARANCE_GENERIC_COMPUTER = const(128)
+
+class BLEUART:
+    def __init__(self, ble, name='mpy-uart', rxbuf=100):
+        self._ble = ble
+        self._ble.active(True)
+        self._ble.irq(handler=self._irq)
+        ((self._tx_handle, self._rx_handle,),) = self._ble.gatts_register_services((_UART_SERVICE,))
+        # Increase the size of the rx buffer.
+        self._ble.gatts_write(self._rx_handle, bytes(rxbuf))
+        self._connections = set()
+        self._rx_buffer = bytearray()
+        self._handler = None
+        self._payload = advertising_payload(name=name, appearance=_ADV_APPEARANCE_GENERIC_COMPUTER)
+        self._advertise()
+
+    def irq(self, handler):
+        self._handler = handler
+
+    def _irq(self, event, data):
+        # Track connections so we can send notifications.
+        if event == _IRQ_CENTRAL_CONNECT:
+            conn_handle, _, _, = data
+            self._connections.add(conn_handle)
+        elif event == _IRQ_CENTRAL_DISCONNECT:
+            conn_handle, _, _, = data
+            if conn_handle in self._connections:
+                self._connections.remove(conn_handle)
+            # Start advertising again to allow a new connection.
+            self._advertise()
+        elif event == _IRQ_GATTS_WRITE:
+            conn_handle, value_handle, = data
+            if conn_handle in self._connections and value_handle == self._rx_handle:
+                self._rx_buffer += self._ble.gatts_read(self._rx_handle)
+                if self._handler:
+                    self._handler()
+
+    def any(self):
+        return len(self._rx_buffer)
+
+    def read(self, sz=None):
+        if not sz:
+            sz = len(self._rx_buffer)
+        result = self._rx_buffer[0:sz]
+        self._rx_buffer = self._rx_buffer[sz:]
+        return result
+
+    def write(self, data):
+        for conn_handle in self._connections:
+            self._ble.gatts_notify(conn_handle, self._tx_handle, data)
+
+    def close(self):
+        for conn_handle in self._connections:
+            self._ble.gap_disconnect(conn_handle)
+        self._connections.clear()
+
+    def _advertise(self, interval_us=500000):
+        self._ble.gap_advertise(interval_us, adv_data=self._payload)
+
+
+# ble = bluetooth.BLE()
+# uart = BLEUART(ble)