USB WS2812B Python control script

usbleds.py

#!/usr/bin/python
import sys
import random
import time
import struct

import usb1

USB_GET_VERSION = 0
USB_SET_LED_COUNT = 1
USB_SET_LED_RGB = 2
USB_UPDATE_LEDS = 3

NUMLEDS = 8

STANDARD_COLORS = (
  '\0\0\0',
  '\xff\0\0',
  '\0\xff\0',
  '\xff\xff\0',
  '\0\0\xff',
  '\xff\0\xff',
  '\0\xff\xff',
  '\xff\xff\xff',
)

context = usb1.USBContext()

devicelist = context.getDeviceList(skip_on_error=True)

handle = None

for device in devicelist:
  try:
    if device.getProduct() == u'usbled':
      handle = device.open()
      break
  except usb1.USBErrorAccess:
    pass
else:
  raise RuntimeError('usbled not found!')

try:
  verraw = handle.controlRead(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
    USB_GET_VERSION, 0, 0, 2)
  version = struct.unpack('H', verraw)[0]
  if version < 0x0100:
    raise RuntimeError('Version of usbled (0x%4h) not supported!'
      % (version,))

  handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
    USB_SET_LED_COUNT, NUMLEDS, 0, '')
  
  for c in STANDARD_COLORS:
    for ix in range(NUMLEDS):
      handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
        USB_SET_LED_RGB, 0, ix, c)
    handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
      USB_UPDATE_LEDS, 0, 0, '')
    time.sleep(0.3)
  
  time.sleep(2)

  while True:
    for i in range(len(STANDARD_COLORS)):
      for ix, color in enumerate(STANDARD_COLORS):
        if (i + ix) % len(STANDARD_COLORS) < NUMLEDS:
          handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
            USB_SET_LED_RGB, 0, (i + ix) % len(STANDARD_COLORS), color)
      handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
        USB_UPDATE_LEDS, 0, 0, '')
      time.sleep(0.05)

except KeyboardInterrupt:
  for x in range(NUMLEDS):
    handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
      USB_SET_LED_RGB, 0, x, '\0\0\0')
  handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE,
    USB_UPDATE_LEDS, 0, 0, '')
  
finally:
  handle.close()