AT42QT2640_14 Datasheet, PDF (41/73 Pages) ATMEL Corporation – 64-key 8-slider/wheel QMatrix FMEA

5.5 Addresses 1025 to 1088 – Slider member / AKS / Burst Length
Table 5-5. Slider member / AKS / Burst Length
Address
Bit 7
Bit 6
Bit 5
Bit 4
1025
SLD
(Key 0)
AKS
(Key 0)
BL
(Key 0)




1088
SLD
AKS
(Key 63) (Key 63)
BL
(Key 63)
Bit 3
Bit 2
Bit 1
Reserved
Reserved
Bit 0
5.5.1
Slider Member – SLD
Sliders and Wheels are constructed from a group of keys. Keys can operate as part of a Slider/Wheel or
independently, as keys, but not both. A Key is declared as being part of a slider/wheel by setting its SLD bit, this
inhibits the normal key processing which would otherwise interfere with the slider operation.
The data set for keys is undefined when used as part of a slider/wheel, and should be ignored.
Other configuration is also required for slider/wheel operation. See setups SLD, SSN and SLEN at a minimum and
also SW, SPH, SF, and SRS. AKS, and FDIL must be disabled for slider/wheel members, and BL must be set
appropriately for slider/wheel members. See the respective sections for details.
SLD default value:
0 (Normal key operation)
SLD Range:
0 (Normal key operation)
1 (Key participates in a wheel/slider)
5.5.2
Adjacent Key Suppression Technology – AKS
This QT2640 incorporates Adjacent Key Suppression (AKS) technology that can be selected on a per-key basis.
AKS technology permits the suppression of multiple key presses based on relative signal strength. This feature
assists in solving the problem of surface moisture which can bridge a key touch to an adjacent key, causing multiple
key presses. This feature is also useful for panels with tightly spaced keys, where a fingertip might inadvertently
activate an adjacent key.
AKS technology works for keys that are AKS-enabled anywhere in the matrix and is not restricted to physically
adjacent keys. The QT2640 has no knowledge of which keys are actually physically adjacent. When enabled for a
key, Adjacent Key Suppression causes detections on that key to be suppressed if any other AKS-enabled key in the
panel has a more negative signal deviation from its reference during the DI process. Once a key reaches detect it
stays in detect as long as the touch remains, regardless of the signal strength on any other AKS-enabled keys.
This feature does not account for varying key gains (burst length) but ignores the actual negative detection threshold
setting for the key. If AKS-enabled keys have different sizes, it may be necessary to reduce the gains of larger keys
to equalize the effects of AKS technology. The signal threshold of the larger keys can be altered to compensate for
this without causing problems with key suppression.
Adjacent Key Suppression works to augment the natural moisture suppression of narrow gated transfer switches
creating a more robust sensing method.
AKS is not supported on slider and wheel elements, and should be configured off at all keys used to construct a
slider/wheel.
AKS Default value:
0 (Off)
AKS Range:
0 (Off)
1 (On)
AT42QT2640 [PRELIMINARY DATASHEET]
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