An example script showing how to interact with Griffin Powermate using pyusb library.

powermate_pyusb_example.py

"""Pyusb with Griffin Powermate.

Linux notes:
    On Debian 8 it requires admin rights to access the powermate device.
    The script can be tested via activating superuser and the virtual
    environment with pyusb and calling the script.

Usage notes:
    dev.read returns the following values in an array:
        0: button state (0 not pressed, 1 pressed)
        1: amount turned. CW: 1, 2, 3 etc, CCW: 255, 254, 253 etc
        2: 0 (always 0)
        3: brightness of the light (0-255)
        4: LED status (pulsing or constant brightness, pulse while sleep)
        5: pulse value (0-255)

"""

import usb.core
import usb.util

VENDOR = 0x077d  # 1917
PRODUCT = 0x0410  # 1040

dev = usb.core.find(idVendor=VENDOR, idProduct=PRODUCT)

if dev is None:
    raise Exception("Could not find Griffin PowerMate.")

if dev.is_kernel_driver_active(0):
    dev.detach_kernel_driver(0)

dev.set_configuration()

# get an endpoint instance
print dev.get_active_configuration()

# %%

# start with light turned off
light = 0
dev.write(0x2, [0x00])

# turn powermate to increase/decrease light level
while dev.read(129, 6, timeout=99999999999)[0] == 0:

    resp = dev.read(129, 6, timeout=99999999999)[1]

    if resp < 127:
        light = (light + resp) % 255
        print resp, light
        dev.write(0x2, [light])

    elif resp >= 127:
        resp = resp - 256  # for opposite direction
        light = (light + resp) % 255
        print resp, light
        dev.write(0x2, [light])