PYTUYO - communicate with MITUTOYO USB-ITN cables from python using pyusb

proof-of-concept code showing how to connect to and request readings from a
mitutoyo indicator via the USB-ITN cable.  Tested on linux.

The USB-ITN cable enumerates as an HID device, but can be used as a Virtual
Comm Port (VCP) by sending data over the control endpoint and reading responses
on the interrupt IN endpoint.  This VCP functionality requires performing an
initial control transfer with 0xA5A5 as wValue.  The USB-ITN then responds to
the host with a single byte data response of 0x01 over the control endpoint.
The device will now respond to various ASCII commands sent via control transfer
data payloads.


In order to communicate on linux the mitutoyo cables need to be recognized and
added to a group that the user has read/write access --

if python3 read.py fails, but sudo python3 read.py works, then you likely have a
permissions issue.  If your user has access to the plugdev group then adding
this text to /etc/udev/rules.d/

############## MITUTOYO USB-ITN-F CABLE ##############
SUBSYSTEM=="usb", ATTRS{idVendor}=="0fe7",\
ATTRS{idProduct}=="4001", MODE="0660", GROUP="plugdev"