MPR121_10 FREESCALE [Freescale Semiconductor, Inc], MPR121_10 Datasheet - Page 31

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

Sensors
Freescale Semiconductor
Case 6
touch was a real touch, but slow enough that initially it is thought better for the baseline not to change at all.
Case 7
the process. The baseline can be set to slowly calibrate a touch from the system preventing keys from becoming stuck. Only the
NHD, NCL and FDL are necessary since the value can never be less than double the MHD.
The system needs the capability to handle environment changes that appear very similar to actual touches. In Case 5, the
This case is when a touch is occurring. While the baseline system does not detect a touch, it is obviously an important part of
C. A delta from the new baseline allows a touch to be accurately detected.
C. Normal baseline filter is engaged.
A. The decrease is the interface being cleared with a wet rag, causing a relatively slow capacitance
B. The baseline begins to increase as the interface becomes dry.
A. The touch is detected which disengages the increasing/decreasing baseline filter but leaves it
B. Even though the touch has not been released it times out and is eventually rejected.
change. The baseline accurately tracks this slow change.
enabled with very slow filtering
A
A
Figure 34.
Figure 35.
B
B
C
C
Baseline
Data
Baseline
Data
MPR121
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