MPR121_10 FREESCALE [Freescale Semiconductor, Inc], MPR121_10 Datasheet - Page 24

• Manufacturer Part Number: MPR121_10
• Description: Proximity Capactive touch Senosr controller
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

MPR121
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Note: In most cases the CDT in this register is not used. It will normally be auto-configured as described in AN3889
average current consumption of the device.
in a very low average current consumption.
While the 1 ms to 128 ms does affect the filtering, the main purposed of adjusting the sample rate would be to change the
From this, it can be seen that the 12 μs up time from the 1 ms samples results in a very low percent of duty cycle. This results
0
Table 21. Filter Configuration Register Field Descriptions
First Filter
Field
CDT
ESI
SFI
7:5
4:3
2:0
1 ms
Charge Discharge Time – The Charge Discharge Time field selects the amount of
time an electrode charges and discharges.
000 Encoding 0 – Invalid
001 Encoding 1 – Time is set to 0.5 μs
010 Encoding 2 – Time is set to 1 μs
~
111 Encoding 7 – Time is set to 32 μs.
Second Filter Iterations – The Second Filter Iterations field selects the number of
samples taken for the second level filter.
00 Encoding 0 – Number of samples is set to 4
01 Encoding 1 – Number of samples is set to 6
10 Encoding 2 – Number of samples is set to 10
11 Encoding 3 – Number of samples is set to 18
Electrode Sample Interval – The Electrode Sample Interval field selects the period
between samples used for the second level of filtering.
000 Encoding 0 – Period set to 1 ms
001 Encoding 1 – Period set to 2 ms
~
111 Encoding 7 – Period set to 128 ms
Figure 22
illustrates this adjustment.
Figure 22.
TIME (ms)
2 ms
Description
3 ms
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