ATAVRQTOUCHX Atmel, ATAVRQTOUCHX Datasheet - Page 13

• Manufacturer Part Number: ATAVRQTOUCHX
• Description: BOARD EVAL CAPACITIVE TOUCH
• Manufacturer: Atmel
• Series: QTouch™r

Specifications of ATAVRQTOUCHX

• Sensor Type: Touch, Capacitive
• Sensing Range: 1 Slider, 1 Wheel, 2 Buttons
• Interface: USB
• Voltage - Supply: 5V, USB
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: AT90USB1287, ATxmega128A1
• Silicon Manufacturer: Atmel
• Silicon Family Name: ATxmega
• Kit Contents: Board
• Svhc: No SVHC (15-Dec-2010)
• Core Architecture: AVR
• Core Sub-architecture: AVR19
• Kit Features: One Slider, One Wheel And 2
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sensitivity: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

5.2 Acquisition Methods
There are two methods available for touch acquisition namely
Libraries for AVR microcontrollers include both acquisition methods. Libraries for ATSAM
microcontrollers include only QTouch acquisition method.
5.2.1
The QTouch acquisition method charges an electrode of unknown capacitance to a known
potential. The resulting charge is transferred into a measurement capacitor (Cs). The cycle is
repeated until the voltage across Cs reaches a voltage Vih. The signal level is the number of
charge transfer cycles it took to reach that voltage. Placing a finger on the touch surface
introduces external capacitance that increases the amount of charge transferred each cycle,
reducing the total number of cycles required for Cs to reach the voltage. When the signal level
(number of cycles) goes below the present threshold, then the sensor is reported to be in
detected.
QTouch acquisition method sensors can drive single or multiple keys. Where multiple keys are
used, each key can be set for an individual sensitivity level. Keys of different sizes and shapes
can be used to meet both functional and aesthetic requirements.
NOTE: It is recommended to keep the size of the keys larger than 6mmx6mm to ensure reliable
and robust measurements, although actual key design requirements also depend on panel
thickness and material. Refer to the ATMEL Capacitive touch sensor design guide for details.
QTouch acquisition method can be used in two ways
QTouch circuits offers high signal-to-noise ratio, very good low power performance, and the
easiest sensor layout.
1. QTouch acquisition method.
2. QMatrix acquisition method.
•
•
QTouch acquisition method
normal touch contact (i.e. when pressing buttons on a panel), and
high sensitivity proximity mode (i.e. when a panel lights up before you actually contact it).
Figure 5-2 : QTouch Acquisition
13