nkro_utils.py

# adapted from adafruit's example
import usb_hid

REPORT_ID = 0x4
REPORT_BYTES = 16 # 128bit, 128keys(without modifiers)
bitmap_keyboard_descriptor = bytes((
		0x05, 0x01,                     # Usage Page (Generic Desktop),
		0x09, 0x06,                     # Usage (Keyboard),
		0xA1, 0x01,                     # Collection (Application),
		0x85, REPORT_ID,                #   Report ID
		# bitmap of modifiers
		0x75, 0x01,                     #   Report Size (1),
		0x95, 0x08,                     #   Report Count (8),
		0x05, 0x07,                     #   Usage Page (Key Codes),
		0x19, 0xE0,                     #   Usage Minimum (224),
		0x29, 0xE7,                     #   Usage Maximum (231),
		0x15, 0x00,                     #   Logical Minimum (0),
		0x25, 0x01,                     #   Logical Maximum (1),
		0x81, 0x02,                     #   Input (Data, Variable, Absolute), ;Modifier byte
		# LED output report
		0x95, 0x05,                     #   Report Count (5),
		0x75, 0x01,                     #   Report Size (1),
		0x05, 0x08,                     #   Usage Page (LEDs),
		0x19, 0x01,                     #   Usage Minimum (1),
		0x29, 0x05,                     #   Usage Maximum (5),
		0x91, 0x02,                     #   Output (Data, Variable, Absolute),
		0x95, 0x01,                     #   Report Count (1),
		0x75, 0x03,                     #   Report Size (3),
		0x91, 0x03,                     #   Output (Constant),
		# bitmap of keys
		0x95, (REPORT_BYTES-1)*8,       #   Report Count (),
		0x75, 0x01,                     #   Report Size (1),
		0x15, 0x00,                     #   Logical Minimum (0),
		0x25, 0x01,                     #   Logical Maximum(1),
		0x05, 0x07,                     #   Usage Page (Key Codes),
		0x19, 0x00,                     #   Usage Minimum (0),
		0x29, (REPORT_BYTES-1)*8-1,     #   Usage Maximum (),
		0x81, 0x02,                     #   Input (Data, Variable, Absolute),
		0xc0                            # End Collection
))

bitmap_keyboard = usb_hid.Device(
	report_descriptor=bitmap_keyboard_descriptor,
	usage_page=0x1,
	usage=0x6,
	report_ids=(REPORT_ID,),
	in_report_lengths=(REPORT_BYTES,),
	out_report_lengths=(1,),
)

def enable_nkro():
	usb_hid.enable(
		(
			bitmap_keyboard,
			usb_hid.Device.MOUSE,
			usb_hid.Device.CONSUMER_CONTROL,
		)
	)