AT42QT1111-AU_14 Datasheet, PDF (31/50 Pages) ATMEL Corporation – 11-key QTouch Touch Sensor IC

7.8 Address 4: Positive Drift Compensation (PDRIFT)
Table 7-6. Positive Drift Compensation
Address
Bit 7
Bit 6
Bit 5
4
0
Bit 4
Bit 3
PDRIFT
Bit 2
Bit 1
Bit 0
When changing ambient conditions cause a change in the key signal, the QT1111 will compensate through its drift
functions. Positive Drift refers to the case where the signal for a key is greater than the reference.
Drift compensation occurs at a rate of 1 count per drift compensation period.
PDRIFT: the drift compensation period, in multiples of 160 ms. The valid range is 0 to 127, where 0 disables positive
drift compensation.
Note: Drift compensation timing is paused while Drift Hold is activated, and continued when Drift Hold has timed
out.
Default value:
6 (960 ms)
7.9 Address 5: Positive Recalibration Delay (PRD)
Table 7-7. Positive Recalibration Delay
Address
Bit 7
Bit 6
Bit 5
5
Bit 4
Bit 3
PRD
Bit 2
Bit 1
Bit 0
If a key signal is determined to be above the positive threshold, the QT1111 will wait for this delay and confirm that
the error condition is still present before initiating a recalibration.
PRD: the positive recalibration delay, in multiples of 160 ms.
Note: All keys are recalibrated in the case of a positive recalibration.
Default value:
6 (960 ms)
7.10 Address 6: Lower Burst Limit (LBL)
Table 7-8. Lower Burst Limit
Address
Bit 7
Bit 6
6
Bit 5
Bit 4
Bit 3
LBL
Bit 2
Bit 1
Bit 0
Normal QTouch signals are in the range of 100 to 1000 counts for each key. The lower burst limit determines the
minimum signal that is considered as a valid acquisition. If the count is lower than the lower burst limit, it is
considered not to be valid and the key is set to an Error state.
Note:
Where a key has a signal of less than the LBL, the key is set to its “no detect” state. If the key signal rises
above LBL, but remains under the detection level (that is: reference signal - detection threshold), the Detect
Integration is applied. In this case the detection is not reported immediately but is delayed until the DI filter
confirms detection.
Default value:
18
AT42QT1111-MU / AT42QT1111-AU [DATASHEET]
31
9571C–AT42–05/2013