NXP Semiconductors MKW01Z128, Reference Manual

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Rs (Bits)
(kΩ)
DVOLT
(Bits) (V)
111 110 101 100 011
5.5 14 32 77 184
11 0.29
10 0.43
01 0.73
00 1.03
The TSI noise detection algorithm shall be done by application software (assume
software poll method is used to check TSI scan status) as described below, note the
values in below steps are just used to illustrated the algorithm flow, the actual value
should be consistent with the valid combinations as shown in the table above.
1. Enable TSI by setting TSI_CS0[TSIEN] bit and select a channel by writing a channel
number to TSI_CS3[TSICH] just as does for normal function mode;
2. Enable noise detection mode by writing 11b to TSI_CS3[STAT_STUP[3:2]]
(STAT_STUP bit 3 and 2 with 11);
3. Initialize the noise RF amplitude and noise detection mode sense duration (T) as
below:
a. Initialize Rs to the max value by writing 011b to TSI_CS2[EXTCHRG] and
DVOLT to the minimum value by writing 11b to TSI_CS2[DVOLT];
b. Set up TSI_CS2[REFCHRG], TSI_CS1[PS] and TSI_CS1[NSCN] bits to set the
noise detection mode sense duration (T). T= (2 x (2
PS
) x NSCN x Cref x ∆V)/
Iref .
NOTE
NOTE: This time needs to be enough to detect the
number of WINDOW bits for the minimum noise
frequency. The minimum value of T (Tmin) is
calculated as below: Tmin = (1)/F
noise_min
;
Where F
noise_min
is the minimum noise frequency (0.15
MHz) and WINDOW is 2. This results in Tmin = 20
µs. Also this algorithm needs to be consistent with the
valid Rs/Dvold combinations in above table.
4. Start TSI scan with software trigger or hardware trigger just as does for normal
function mode
5. Wait until TSI scan is complete (TSI_CS0[EOSF] = 1);
6. Read TSI counter value in TSI_CNTH:TSI_CNTL and then clear TSI_CS0[EOSF]
flag;
Chapter 35 Touch Sensing Input (TSI)
MKW01Z128 MCU Reference Manual, Rev. 3, 04/2016
Freescale Semiconductor, Inc. 705