• Set SETCLK<1:0> to ‘01’ to get Fclkmain = 16.65MHz. Then the period of
mainclock is Tclkmain.
• Set SSC_MODE<1:0> to ‘00’ to enable PRBS SSC mode.
• Set BASE_NOCHARGE_NUM<3:0> to ‘0100’ to set t1 = 5*Tclkmain.
• Set CHARGE_NUM<3:0> to ‘0110’ to set t3 = 7*Tclkmain.
• Set PRBS_OUTSEL<3:0> to ‘0110’ to set t2 range from 1* Tclkmain to 6*
Tclkmain. The average t2 is 3.5* Tclkmain.
• Keep other registers in TSI_SSC0, TSI_SSC1 and TSI_SSC2 as default value.
• Then, Fsw = 16.65MHz/(5+3.5+7) = 1.074MHz. Fsw is spectrum spread pulse.
48.5.9 Reference voltage
Reference voltage is used to setup ramp up threshold. It decides TSICNT and
SCANTIME. The TSI module offers dual reference voltages for both comparators. The
internal reference voltage can work in low power modes even when the MCU regulator is
partially powered down, which is ideally for low-power touch detection.
The reference voltages are configurable upon the setting of TSI_GENCS[DVOLT]. The
following table shows the all the delta voltage configurations.
Table 48-5. Delta voltage configuration
DVOLT
V
p
(V)
V
m
(V)
Δ
V (V)
00
0.3
1.3
1.0
01
0.3
1.6
1.3
10
0.3
1.9
1.6
11
0.3
2.3
2.0
48.5.10 End of scan
As a scan starts, [SCNIP] bit is set to indicate scan is in progress. When the scan
completes, the [EOSF] bit is set. Before clearing the [EOSF] bit, the value in
TSI_DATA[TSICNT] must be read. If TSI_GENCS[TSIIEN] and TSI_GENCS[ESOR]
are set, and TSI_DATA[DMAEN] is not set, an interrupt is submitted to CPU for post-
processing immediately. The interrupt is also optional to wake MCU to execute ISR if it
is in low power mode. When DMA function is enabled by setting TSI_GENCS[TSIIEN]
and TSI_GENCS[ESOR], as soon as scan completes, a DMA transfer request is asserted
to DMA controller for data movement, generally, DMA engine will fetch TSI conversion
Chapter 48 Touch Sensing Input (TSI)
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors
1305
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