Rainbow Electronics AT42QT1110-AZ - Manual (Page 37)

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9570H–AT42–02/10
AT42QT1110-MZ/AT42QT1110-AZ
7.18 Addresses 31–41: Negative Drift Compensation (NDRIFT)/Negative Recalibration Delay (NRD)
KEY_n_NDRIFT: the negative drift compensation for key n (where n is 0–10).
When changing ambient conditions cause a change in the key signal, the QT1110 will
compensate through its drift functions. “Negative Drift” refers to the case where the signal for a
key is lower than the reference. Drift compensation occurs at a rate of 1 count per drift
compensation period. The entered number is a multiple of 320 ms.
Note that as a key touch, or an approaching touch, naturally causes a negative change in the
signal, negative drift should be carried out at a much slower rate than positive drift. Otherwise, a
slowly approaching finger will not cause a touch detection, as the falling signal could be
compensated through the negative drift mechanism.
Note: Drift compensation timing is paused while Drift Hold is activated, and continues when
Drift Hold has timed out.
KEY_n_NRD: the negative recalibration delay for key n (where n is 0–10).
In order to avoid a situation where a key remains “stuck” in detect due to, for example, changing
environmental conditions, the “Negative Recalibration Delay” sets an upper limit on how long a
key can remain “touched”. When this time is exceeded, the QT1110 (that is, all keys) is
recalibrated, taking this key (and any others which are in detect) out of detection. This delay is
set in a multiple of 2560 ms.
Note: A setting of “0” disables the NRD Timeout.
Default KEY_n_NDRIFT value: 7 (2240 ms)
Default KEY_n_NRD value: 10 (25.6 seconds)
Table 7-18. Negative Drift Compensation/Negative Recalibration Delay
Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
31 KEY_0_NDRIFT KEY_0_NRD
32 KEY_1_NDRIFT KEY_1_NRD
33 KEY_2_NDRIFT KEY_2_NRD
34 KEY_3_NDRIFT KEY_3_NRD
35 KEY_4_NDRIFT KEY_4_NRD
36 KEY_5_NDRIFT KEY_5_NRD
37 KEY_6_NDRIFT KEY_6_NRD
38 KEY_7_NDRIFT KEY_7_NRD
39 KEY_8_NDRIFT KEY_8_NRD
40 KEY_9_NDRIFT KEY_9_NRD
41 KEY_10_NDRIFT KEY_10_NRD