MK712

TOUCH SCREEN CONTROLLER

TOUCH SCREEN CONTROL

IDT™ TOUCH SCREEN CONTROLLER

8

MK712

REV N 051310

Recommended Method for Reading Points

If the user is pressing lightly on the touch screen, it is likely that the screen contact will be intermittent. The screen

will bounce, causing false points. This effect can be reduced by insuring that the screen is touched both before and

after a conversion. By doing this, the first and last point in a series of points are discarded. The following algorithm

checks that a point has valid touches both before and after a conversion, and it distinguishes between

change-in-touch interrupts and conversion complete interrupts. Register 6 bits 0, 1, and 2 must all be true (logical

1) in order to use this method.

Warning–When Using a Switching Regulator Power Supply

When using the MK712 in a system where the power is supplied by a switching regulator, do not perform screen

conversions when the regulator is operating in the power saving mode. Some switching regulators feature a low

power mode (for example, Linear Technology’s “Burst Mode”) where the output is turned on and off in order to save

power. The extra power supply noise generated when using this mode causes spurious data points to be returned

from the MK712, so it should be disabled when the MK712 is doing screen conversions.