demos: Add ws2812 BLE demo

demos/ble-ws2812-card10.py

+import ws2812, gpio, bluetooth, time, display
+from micropython import const
+
+_IRQ_GATTS_WRITE = const(3)
+
+WS2812_SERVICE_UUID = \
+    bluetooth.UUID("23230300-2342-2342-2342-234223422342")
+SET_ALL = (
+    bluetooth.UUID("23230301-2342-2342-2342-234223422342"),
+    bluetooth.FLAG_WRITE
+)
+WS2812_SERVICE = (
+    WS2812_SERVICE_UUID,
+    (SET_ALL,)
+)
+
+def irq(event, data):
+    if event == _IRQ_GATTS_WRITE:
+        conn_handle, value_handle = data
+        value = ble.gatts_read(value_handle)
+        ws2812.set_all(gpio.WRISTBAND_3, [value] * 3)
+
+if __name__ == "__main__":
+    display.open().backlight(0)
+    gpio.set_mode(gpio.WRISTBAND_3, gpio.mode.OUTPUT)
+
+    ble = bluetooth.BLE()
+    ble.active(True)
+    ble.irq(irq)
+    ble.gatts_register_services((WS2812_SERVICE,))
+
+    print("Waiting for connection!")
+
+    while True:
+        time.sleep(1)

demos/ble-ws2812-host.py

+#!/usr/bin/env python3
+import bluepy
+import time
+import colorsys
+
+p = bluepy.btle.Peripheral("CA:4D:10:01:ff:64")
+c = p.getCharacteristics(
+    uuid='23230301-2342-2342-2342-234223422342')[0]
+
+hue = 0
+while 1:
+    r,g,b = colorsys.hsv_to_rgb(hue, 1, 0.1)
+    c.write(b"%c%c%c" %
+        (int(r*255), int(g*255), int(b*255)), True)
+    time.sleep(.1)
+    hue += 0.1
+