ATAVRQTOUCHX Atmel, ATAVRQTOUCHX Datasheet - Page 16

• 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

For example, if recalibration threshold (one of the global settings) of QMatrix acquisition method
is set as 1, all QMatrix sensors will have recalibration threshold of 1.
5.3.1
Recalibration threshold is the level above which automatic recalibration occurs. Recalibration
threshold is expressed as a percentage of the detection threshold setting. This setting is an
enumerated value and its settings are as follows:
However, an absolute value of 4 is the hard limit for this setting. For example, if the detection
threshold is say, 40 and the Recalibration threshold value is set to 4. This implies an absolute
value of 2 (40 * 6.25% = 2.5), but this is hard limited to 4.
Setting
Recalibration threshold
5.3.2
The QTouch Library features a detect integration mechanism, which acts to confirm detection in a
robust fashion. The detect integrator (DI) acts as a simple signal filter to suppress false detections
caused by spurious events like electrical noise.
A counter is incremented each time the sensor delta has exceeded its threshold and stayed there
for a specific number of acquisitions, without going below the threshold levels. When this counter
reaches a preset limit (the DI value) the sensor is finally declared to be touched. If on any
acquisition the delta is not seen to exceed the threshold level, the counter is cleared and the
process has to start from the beginning. The DI process is applicable to a ‘release’ (going out of
detect) event as well.
For example, if the DI value is 10, then the device has to exceed its threshold and stay there for
10 acquisitions in succession without going below the threshold level, before the sensor is
declared to be touched.
Setting
5.3.3
Drift Hold Time (DHT) is used to restrict drift on all sensors while one or more sensors are
activated. It defines the length of time the drift is halted after a key detection.
16
•
•
•
•
•
Recalibration Threshold
Setting of 0 = 100% of detect threshold (RECAL_100)
Setting of 1 = 50% of detect threshold (RECAL_50)
Setting of 2 = 25% of detect threshold (RECAL_25)
Setting of 3 = 12.5% of detect threshold (RECAL_12_5)
Setting of 4 = 6.25% of detect threshold (RECAL_6_25)
Detect Integration
DI
Drift Hold Time
Variable
name
qt_di
Variable name
qt_recal_threshold
Data Type
uint8_t
Unit
Data
Type
uint8_t
Cycles
Unit
Enum
Min
Min Max
4
0
8207J-AT42-02/11
Detect
threshold
Max
255
Typical
1
Typical
4