CAP1005 Datasheet, PDF (37/53 Pages) SMSC Corporation – 5 and 6 Channel Capacitive Touch Sensor

5 and 6 Channel Capacitive Touch Sensor
Datasheet
before the next channel is sampled and the result is averaged over the number of samples measured
before updating the measured results.
For example, if CS1, CS2, and CS3 are sampled during the sensor cycle, and the AVG[2:0] bits are
set to take 4 samples per channel, then the full sensor cycle will be: CS1, CS1, CS1, CS1, CS2, CS2,
CS2, CS2, CS3, CS3, CS3, CS3.
Table 5.16 AVG Bit Decode
AVG[2:0]
2
1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
NUMBER OF SAMPLES TAKEN
0
PER MEASUREMENT
0
1
1
2
0
4
1
8 (default)
0
16
1
32
0
64
1
128
Bit 2 - SAMP_TIME - Determines the time to take a single sample.
„ ‘0’ - The sampling time is ~2.56ms.
„ ‘1’ (default) - The sampling time is ~1.28ms.
Bits 1 - 0 - CYCLE_TIME[1:0] - Determines the overall cycle time for all measured channels during
normal operation as shown in Table 5.17. All measured channels are sampled at the beginning of the
cycle time. If additional time is remaining, then the device is placed into a lower power state for the
remaining duration of the cycle.
Table 5.17 CYCLE_TIME Bit Decode
CYCLE_TIME[1:0]
1
0
OVERALL CYCLE TIME
0
0
35ms
0
1
70ms (default)
1
0
105ms
1
1
140ms
APPLICATION NOTE: The programmed cycle time is only maintained if the total averaging time for all samples is
less than the programmed cycle. The AVG[2:0] bits will take priority so that if more samples
are required than would normally be allowed during the cycle time, the cycle time will be
extended as necessary to accommodate the number of samples to be measured.
SMSC CAP1005 / CAP1006
37
DATASHEET
Revision 1.1 (08-05-09)