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_temperature.py

@@ -0,0 +1,76 @@
+# This example demonstrates a simple temperature sensor peripheral.
+#
+# The sensor's local value updates every second, and it will notify
+# any connected central every 10 seconds.
+
+import bluetooth
+import random
+import struct
+import time
+from ble_advertising import advertising_payload
+
+from micropython import const
+_IRQ_CENTRAL_CONNECT                 = const(1 << 0)
+_IRQ_CENTRAL_DISCONNECT              = const(1 << 1)
+
+# org.bluetooth.service.environmental_sensing
+_ENV_SENSE_UUID = bluetooth.UUID(0x181A)
+# org.bluetooth.characteristic.temperature
+_TEMP_CHAR = (bluetooth.UUID(0x2A6E), bluetooth.FLAG_READ|bluetooth.FLAG_NOTIFY,)
+_ENV_SENSE_SERVICE = (_ENV_SENSE_UUID, (_TEMP_CHAR,),)
+
+# org.bluetooth.characteristic.gap.appearance.xml
+_ADV_APPEARANCE_GENERIC_THERMOMETER = const(768)
+
+class BLETemperature:
+    def __init__(self, ble, name='mpy-temp'):
+        self._ble = ble
+        self._ble.active(True)
+        self._ble.irq(handler=self._irq)
+        ((self._handle,),) = self._ble.gatts_register_services((_ENV_SENSE_SERVICE,))
+        self._connections = set()
+        self._payload = advertising_payload(name=name, services=[0x181A], appearance=_ADV_APPEARANCE_GENERIC_THERMOMETER)
+        self._advertise()
+
+    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
+            self._connections.remove(conn_handle)
+            # Start advertising again to allow a new connection.
+            self._advertise()
+
+    def set_temperature(self, temp_deg_c, notify=False):
+        # Data is sint16 in degrees Celsius with a resolution of 0.01 degrees Celsius.
+        # Write the local value, ready for a central to read.
+        self._ble.gatts_write(self._handle, struct.pack('<h', int(temp_deg_c * 100)))
+        if notify:
+            for conn_handle in self._connections:
+                # Notify connected centrals to issue a read.
+                self._ble.gatts_notify(conn_handle, self._handle)
+
+    def _advertise(self, interval_us=500000):
+        self._ble.gap_advertise(interval_us, adv_data=self._payload)
+
+
+def demo():
+    ble = bluetooth.BLE()
+    temp = BLETemperature(ble)
+
+    t = 25
+    i = 0
+
+    while True:
+        # Write every second, notify every 10 seconds.
+        i = (i + 1) % 10
+        temp.set_temperature(t, notify=i == 0)
+        # Random walk the temperature.
+        t += random.uniform(-0.5, 0.5)
+        time.sleep_ms(1000)
+
+
+if __name__ == '__main__':
+    demo()