README

The purpose of this tool is to support the calibration of USB touchscreens as a
preparation for using USB touchscreens with Circle applications. It depends on
your touchscreen model, if a calibration is required. Some touchscreens directly
send screen coordinates and do not need to be calibrated. If you are unsure, you
can run this tool and it will tell you, if a calibration is required.

This tool will be built as any Circle application. First build the Circle
libraries by entering "makeall" from Circle project root and then do "make" in
this directory. Install the kernel image on the SD card along with the firmware
files. Some touchscreens need a special configuration in the config.txt file.
This information is given in the product information of your touchscreen.

When you start your Raspberry Pi with this tool installed, it will try to detect
your touchscreen with USB interface first. If this detection fails, a message is
displayed, and your touchscreen cannot be used with Circle. Otherwise the tool
will prompt you, to press four specific points on the screen. Afterwards it will
tell you, if a configuration is required and which values have to be set. If so,
the file cmdline.txt on the SD card has to be edited and the following option
has to be added in the first line of the file (example):

touchscreen=140,3960,340,3920

Now you can install the application, which uses the USB touchscreen and run it.
