Low impact support for multitouch, example app

[davidthings]

On my Adafruit 2.8" TFT Breakout Board with Capacitive Touch, the touch sensor certainly does register more than one touch.

This modification to the library adds a single routine

  uint8_t readMultiData(uint8_t *id0, uint16_t *x0, uint16_t *y0, uint8_t *id1, uint16_t *x1, uint16_t *y1 );

To read both touch locations, and return how many touches are registered.

The example (Multitouch.ino) uses this new function to implement a fairly complete multitouch system with regular events:

  TouchDown
  TouchUp
  TouchMove
  Tap
  DoubleTap

And two finger events

  Zoom
  Scroll

The user can drag and drop a shape, pinch and zoom it, double tap it to change shape, and swipe up and down to change color.

This is tested on a Teensy 3.1 connected to the Adafruit 2.8 TFT Breakout board.

(Sorry about the gratuitous changes to the main files - my editor seems to like removing trailing spaces from lines)

[andholz]

Hi,
Great contribution imho, thank you! Looking forward to testing this more, comes just in time for a GUI I'm working on.

Cheers!

[actuel41]

This doesn't seem to work for my touchscreen because I can't get the FT6206 to recognize two touches. The second touch XY registers are always invalid/empty (0xFF). When I use two fingers it saves the XY value of a point halfway in-between. Is there some initialization I'm missing?