save_to_device.py

#!/usr/bin/python3

# https://pyusb.github.io/pyusb/ -- python3-usb
import usb.core

## Focusrite(R) Scarlett 18i6
device = usb.core.find(idVendor= 0x1235, idProduct=0x8004)

if device is None:
  raise ValueError('Device not found')

try:
  device.detach_kernel_driver(0)
except:
  pass

def ctrl_cmd(cmd, wValue, wIndex, data):
  try:
    assert device.ctrl_transfer(0x21, cmd, wValue, wIndex, data) == len(data)
  except:
    raise ValueError('request failed')

# save current config on the 18i6 to be restored after power-cycles
ctrl_cmd(0x03, 0x005a, 0x3c00, [0xa5])

# vim: set ts=2 sw=2 et: