AT42QTAN0040 Datasheet, PDF (1/14 Pages) ATMEL Corporation – Driving the AT42QT2160 QMatrix Sensor IC

Driving the AT42QT2160 QMatrix Sensor IC
1. Introduction
This application note shows how the AT42QT2160-MMU (QT2160) 16-key QMatrix™
Sensor IC can be connected to a microprocessor to provide touch input functionality.
Example code is provided to demonstrate how easily the QT2160 can be incorporated
into a design. The code can be run “as is” or used as a starting point for QT2160-
based projects. The example compiles to under 1 Kbyte of code including all
necessary I²C-compatible driver functions.
The example code is written in the C programming language and can easily be
adapted for many processor types. See Section 6 on page 8 for a listing of the
complete program.
Figure 1-1. Circuit Configuration for the Example Project
P0.3
P0.7
P0.6
Host MCU
Vdd
CHANGE
SCL
SDA
GPIO3
GPO3
GPO2
GPO1
GPO0
QT2160
Vdd
8 Discrete Keys
(keys 8 – 15)
5-Key Slider
(keys 0 – 4)
QMatrix Key
Array
Driving the
AT42QT2160
QMatrix Sensor
IC
Application Note
AT42QTAN0040
2. Overview of the QT2160
2.1 Introduction
The QT2160 is designed for use with up to 16 keys and a slider (constructed from 2
keys up to 8 keys). There are three dedicated general-purpose input/outputs (GPIO),
which can be used as inputs (for example, for mechanical switches) or as driven
outputs. There are eight shared general-purpose outputs (GPO). Pulse switch
modulation (PWM) control can be applied to all GPIO and GPO pins.
Keys are configured in a matrix format that minimizes the number of required scan
lines and device pins. The key electrodes can be designed into a conventional printed
circuit board (PCB) or flexible printed circuit board (FPCB) as a copper pattern, or as
printed conductive ink on plastic film. The QT2160 can be fine tuned to optimize
operation with the electrode design.
Full details of the QT2160 can be found in the QT2160 datasheet, which should be
read in conjunction with this application note.
10702A–AT42–07/08