Add Touchscreen Calibrator Example

[CedarGroveStudios]

A simple CircuitPython DisplayIO resistive touchscreen calibrator for Adafruit built-in displays. To use, run as a standalone module, include the following line in the calling module, or type into the REPL:

import touch_calibrator_built_in

Operational paramaters such as screen rotation and REPL-only measurement display can be set in the operational paramaters portion of the module.

When the test screen appears, use a stylus to swipe to the four edges of the visible display area. As the screen is calibrated, the small red square tracks the stylus tip (when REPL_ONLY=False). Minimum and maximum calibration values will display on the screen and in the REPL. The REPL values can be copied and pasted into the target code's touchscreen instantiation statement.

The calibration values are measured for a display rotation of zero degrees. To use the calibration values in the target, correlate the touchscreen pins and the calibration values. The order of the calibration tuples is determined by the display rotation value.

For example, a calibration tuple of ((4951, 58951), (8080, 57071)) would be inserted into the display instantiation statement in the order shown, depending on display orientation:

[FoamyGuy]

I think we need the examples to follow the pattern of starting the filename with the name of the library so for example maybe touchscreen_calibrator_built_in.py

[FoamyGuy]

Looks good to me. Thank you @CedarGroveStudios!