4. Calibrate gain in the appropriate Registers GAIN
n
(Addresses
0x0E
,
0x10
,
0x12
,
0x14
). The gain setting
can be used to tune the sensitivity of the touch button. GAIN
n
is a 6-bit field with 64 different gain levels
corresponding to normalized gains between 1 and 232. A good mechanical and sensor design typically
requires a gain level of around 32 to 50, corresponding to relative gains of 16 to 76 (normalized to gain level
of 0). Use the following sequence to determine the appropriate gain for each button:
• Apply minimum desired force to the button.
• Read initial DATA
n
value after the button press. Note that the baseline tracking will affect this value.
• Calculate gain factor required to increase DATA
n
to the programmed threshold (default is 160).
to find the required gain setting.
5. Enable special features to mitigate button interference if there is any, in Registers BTPAUSE_MAXWIN,
TWIST, COMMON_DEFORM (Addresses
0x16
,
0x19
,
0x1A
).
For more information on inductive touch system design, including mechanical design and sensor electrical
design, refer to
Inductive Touch System Design Guide
.
8.2.1.3 Application Curves
shows a sequence of button presses of 150 grams force, two presses to Channel 0, then two
presses to Channel 1. Each button press response is greater than the threshold.
Time (s)
Convers
ion D
ATA
0
2
4
6
8
-50
0
50
100
150
200
250
300
350
400
D009
Channel 0
Channel 1
Threshold
Figure 8-16. Conversion DATA vs Time for Channels 0 and 1
SNOSDD0 – DECEMBER 2021
50
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