User Manual

36
9570H–AT42–02/10
AT42QT1110-MZ/AT42QT1110-AZ
KEY_n_NTHR: the negative threshold for key n (where n is 0–10).
The negative threshold determines how much the signal must fall (compared to the reference)
before a key is considered to be “In Detect”. This level will generally need to be tuned
individually for each key. To disable an individual key, set the threshold for that key to 0.
KEY_n_NHYST: the negative hysteresis applied to key n detection threshold (where n is
0 – 10).
Negative Hysteresis operates as a “modifier” for the negative threshold in order to provide a
greater degree of control over the detection of a “Touch”. When a key signal is first detected as
being under the negative threshold, the threshold is reduced by a factor corresponding to the
selected negative hysteresis. This means that the key will not go in and out of detection when
the signal is on the borderline between drift-compensation or touch detection.
The settings for negative hysteresis are:
00 No change to negative threshold
01 12.5% reduction in negative threshold
10 25% reduction in negative threshold
11 37.5% reduction in negative threshold
Default KEY_n_NTHR value: 10 counts
Default KEY_n_NHYST value: 2 (25 percent)
7.17 Address 30: Extend Pulse Time
HIGH_TIME: Number of µs to extend the high pulse time.
LOW_TIME: Number of µs to extend the low pulse time.
25 KEY_6_NTHR KEY_6_NHSYT
26 KEY_7_NTHR KEY_7_NHSYT
27 KEY_8_NTHR KEY_8_NHSYT
28 KEY_9_NTHR KEY_9_NHSYT
29 KEY_10_NTHR KEY_10_NHSYT
Table 7-16. Negative Threshold/Negative Hysteresis (Continued)
Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Table 7-17. Extend Pulse Time
Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
30 HIGH_TIME LOW_TIME