TSI software configurations
KE15Z Touch Sensing Interface, User's Guide, Rev. 0, 12/2016
16
NXP Semiconductors
There’re examples for scan time configurations as attached below. Given the NSTEP is 95 and Tnstep is
90us by the measurement of single scan.
Example 1, the Decimation, Order, and Cutoff are configured as 1, then the final scan result is 95, as TSI
performs scan operation for one time, and the scan time is 90us.
Example 2, change the Decimation to 2, then the final scan result becomes 190, as TSI performs scan
twice, and the scan time is 159us, about twice of the previous 90us.
Example 10, is recommended. Change the order to 2, then the final scan result becomes 95*64=6080,
but TSI only performs scan for 8*2=16 times, and the scan time is 1128us, saving a lot of time by
setting order =2.
3.2.3. Sensitivity boost
Mutual capacitive mode supports sensitivity boost. Different to self-capacitive mode, mutual-capacitive
mode implement sensitivity boost by changing the current, which is configurable in register
TSI_MUL0[M_SEN_BOOST]. The current value ranges from 0uA to 62uA.
From the configuration above, we can find out that the boost current is the key configuration to the
sensitivity boost feature, as the boost current increases, the sensitivity becomes better, which means it’s
easier to recognize touch event, as showing in the figure below.
Decimation
Order
Cutoff
NSTEP
Multiple
Scan
Result
Scan
Number
TSI IP
Performs
Scan
Time
(us)
95
90
1
1
1
1
95
1
90
95
90
2
1
1
2
190
2
159
95
90
4
1
1
4
380
4
297
95
90
8
1
1
8
760
8
574
95
90
16
1
1
16
1520
16
1128
95
90
32
1
1
32
3040
32
2235
95
90
1
2
1
1
95
2
159
95
90
2
2
1
4
380
4
297
95
90
4
2
1
16
1520
8
574
95
90
8
2
1
64
6080
16
1128
95
90
8
2
2
32
3040
16
1128
NSTEP
Tnstep
(us)
Configurations
Result
Variable
Register
Descriptions
Sensitivity Boost Current
TSI_MUL0[M_SEN_BOOST]
Choose the sensitivity boost current to change sensitivity
