CAP1214 datasheet(75/107 Pages) MICROCHIP

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Multiple Channel Capacitive Touch Sensor and LED Driver

Datasheet

SMSC CAP1214

Revision 1.0 (08-30-10)

DATASHEET

6.37

Sampling Configuration Register

The Sampling Configuration Register controls the length of the sampling window of selected Capacitive

Touch Sensor channels as indicated in the Sampling Channel Select register.

Increasing the sampling window time will have two effects. The first effect will be to increase the

effective sensitivity of that particular channel so that a touch may be detected with a smaller

ΔC.

However, at the larger sampling times, the resolution of the measurement is reduced.

The second effect will be increase the overall round robin rate (and all timing associated with the round

robin rate such as re-calibration times, repeat rate times, and maximum duration times).

All Capacitive Touch Sensors default to a sampling time of 2.5ms. Increasing the sampling time of any

single channel will increase the overall polling cycle by the same amount.

Bits 2 - 0 - OVERSAMP_RATE[2:0] - Determine the time to take a single sample. This setting applies

to all selected sensors.

6.38

Sensor Base Count Registers

Table 6.55 Sampling Configuration Register

ADDR

R/W

DEFAULT

4Fh

R/W

Sampling

Configuration

-----

OVERSAMP_RATE[2:0]

00h

Table 6.56 OVERSAMP_RATE Bit Decode

OVERSAMP_RATE[2:0]

SENSOR SAMPLING

TIME

40ms

20ms

10ms

5ms

2.5ms (default)

1.28ms

0.64ms

0.32ms

Table 6.57 Sensor Base Count Registers

ADDR

R/W

DEFAULT

50h

Sensor 1 Base

Count

128

00h

51h

Sensor 2 Base

Count

128

00h

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