Purpose: 
This examples shows the usage of the analog comparator in the LPC11Axx parts
for a frequency counter / zero crossing detection application.

Running mode:
* Build and debug program

Note:
This example has been tested on the IAR LPC11A14-SK board.
Projects are provided for LPCXPresso, Keil uVision and IAR Embedded Workbench.
It has been tested using:
- LPCXpresso 4.2.3.292
- Keil uVision 4.53
- IAR Embedded Workbench 6.40.1.3812

Pins used:
ACMP_I3(P0_16) is the input on which the frequency is measured.
P0_31 is used for the User Button.

How to use it ?
After startup, the system auto-calibrates the comparator for 1 second for best
performance. The frequency and duty cycle of the input signal is then measured
and displayed on the LCD and UART periodically. The auto-calibration can be
repeated by pressing the User Button.
