MTCH6102 datasheet(21/45 Pages) MICROCHIP

21 / 45 page

 2014 Microchip Technology Inc.

DS40001750A-page 21

MTCH6102

13.0 BASELINE

Capacitive touch principles rely on analyzing a change

in capacitance from a previously-stored baseline value

(sometimes referred to as a calibration value). Baseline

routines and behavior can be tweaked using the

registers listed in Table 13-1.

13.1

BS Bit (CMD Register)

The BS bit forces the current sensor values to be

stored as the baseline values, disregarding the

constraints

BASEPOSFILTER

and

BASENEGFILTER.

13.2

BASEINTERVAL

It represents the number of touch frames between

baseline sampling. Data that is sampled will be applied

at the next baseline interval, provided that a touch has

not occurred between the two.

If at any point, the touch threshold is breached, the

baseline counter is reset, and a full interval without a

touch must occur before baselining resumes.

Note that this value is specified in terms of the number

of touch frames, so any changes in frame rate should

take this into consideration by raising or lowering this

interval accordingly.

13.3

BASEPOSFILTER/BASENEGFILTER

The positive and negative filters act as slew-rate

limiters for a new baseline being applied. For example,

if the new baseline value is larger than the previous by

a value of 35, and the BASEPOSFILTER is set to 20

(default), the new baseline will only be increased by 20.

Use of these registers helps prevent unwanted spikes

in the baseline value.

13.4

BASEFILTERTYPE/

BASEFILTERSTRENGTH

Baseline acquisition frames follow the same filter type

and strength parameters as normal acquisition filters,

defined

Section 11.3

“FILTERTYPE/FILTER-

STRENGTH”.

TABLE 13-1:

REGISTERS ASSOCIATED WITH BASELINE

Address

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2 Bit 1

Bit 0

Default

0x04

DEF

CFG

MFG

-BS

0x2D

BASEINTERVALL

0x2E

BASEINTERVALH

0x2F

BASEPOSFILTER

0x30

BASENEGFILTER

0x33

BASEFILTERTYPE

0x34

BASEFILTERSTRENGTH

MTCH6102 Datasheet(PDF) 21 Page - Microchip Technology

MTCH6102 Datasheet(HTML) 21 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Datasheet Download

Link URL