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AT42QT1085 [DATASHEET]
9625D–AT42–05/2013
2. Overview
2.1 Introduction
The AT42QT1085 (QT1085) is an easy to use QTouchADC mode sensor IC based on Atmel principles for robust
operation and ease of design. It is intended for any touch-key application.
There are four dedicated channels configured as keys (Key 0 – Key 3). There are 12 dedicated GPIO channels
(GPIO_0 – GPIO_11).
Another four channels can be configured as keys or GPIO channels (Key 4 – Key 7 or GPIO 12 – GPIO 15).
The QT1085 is capable of detecting proximity or touch on the channels configured as keys.
The keys can be constructed in different shapes and sizes. Refer to the Touch Sensors Design Guide and
Application Note QTAN0079, Buttons, Sliders and Wheels Sensor Design Guide, for more information on
construction and design methods (both downloadable from the Atmel website).
Each GPIO channel may be configured as a digital input or output. In output mode, a GPIO pin may be set to output
a PWM signal at any of 16 duty cycles (4-bit PWM). The QT1085 allows electrodes to project sense fields through
any dielectric such as glass or plastic.
This device has many advanced features which provide for reliable, trouble-free operation over the life of the
product. In particular the QT1085 features advanced self-calibration, drift compensation, and fast thermal tracking.
The QT1085 can tolerate some fluctuations in the power supply, and in many applications will not require a
dedicated voltage regulator.
A full haptics engine is integrated into the device, allowing feedback effects to be triggered on key detection or
directly activated by a host microcontroller.
The QT1085 includes all signal processing functions necessary to provide stable sensing under a wide variety of
changing conditions. Only a few external parts are required for operation and no external Cs capacitors are required.
The QT1085 modulates its acquisition pulses in a spread-spectrum fashion in order to heavily suppress the effects of
external noise, and to suppress RF emissions. This provides greater noise immunity and eliminates the need for
external sampling capacitors, allowing touch sensing using a single pin.
2.2 Resources
The following document provides essential information on configuring the QT1085:
AT42QT1085 Protocol Guide
Other documents that may also be useful (available by contacting the Atmel Touch Technology division) are listed in
“Associated Documents” on page 28.
2.3 User Interface Layout and Options
2.3.1 Keys
There are eight keys available. Each can be individually enabled or disabled by setting a bit in the Key T13 object
(one for each key).
2.3.2 GPIO Ports
There are 12 dedicated configurable General Purpose Input Output (GPIO) pins. Up to four additional GPIO pins can
be achieved by replacing four of the keys. The GPIO pins can be enabled or disabled by setting a bit in the GPIO
Configuration T29 object.
