MPR031EPR2 Freescale, MPR031EPR2 Datasheet - Page 23

• Manufacturer Part Number: MPR031EPR2
• Manufacturer: Freescale

Specifications of MPR031EPR2

• Lead Free Status / RoHS Status: Compliant

Sensors
Freescale Semiconductor
9
9.1
The MPR03X uses a threshold based system to determine when touches occur. This section will describe that mechanism.
9.2
When a touch pad is pressed, an increase in capacitance will be generated. The resulting effect will be a reduction in the ADC
counts. When the difference between the second level filter value and the third level filter value is significant, the system will
detect a touch. When a touch is detected, there are a couple of effects: the third level filter output becomes fixed (refer to
Section
The touch detection system is controlled using two threshold registers for each independent electrode. The Touch Threshold
register represents the delta at which the system will trigger a touch. The Release Threshold represents the difference at which
a release would be detected. In either case the system will respond by changing the previously mentioned items.
9.2.1
The Touch Threshold Register is used to set the touch threshold for each of the electrodes. The address of the ELE0 Touch
Threshold Register is 0x29. The address of the ELE1 Touch Threshold Register is 0x2B. The address of the ELE2 Touch
Threshold Register is 0x2D.
9.2.2
The Release Threshold Register is used to set the release threshold for each of the electrodes. The address of the ELE0 Release
Threshold Register is 0x2A. The address of the ELE1 Release Threshold Register is 0x2C. The address of the ELE2 Release
Threshold Register is 0x2E.
Table 17. Touch Threshold Register Field Descriptions
Table 18. Release Threshold Register Field Descriptions
8.4), an interrupt is generated (refer to
Touch Detection
Introduction
Thresholds
Touch Threshold Register
Release Threshold Register
Reset:
Reset:
Field
Field
RTH
TTH
7:0
7:0
W
W
R
R
7
0
7
0
= Unimplemented
= Unimplemented
Touch Threshold – The Touch Threshold Byte sets the trip point for detecting a
touch.
00000000 Encoding 0
~
11111111 Encoding 255
Release Threshold – The Release Threshold Byte sets the trip point for detecting
a touch.
00000000 Encoding 0
~
11111111 Encoding 255
6
0
6
0
Figure 31. Release Threshold Register
Figure 30. Touch Threshold Register
Section
5
0
5
0
6), and the touch status register
4
0
4
0
RTH
TTH
Description
Description
3
0
3
0
2
0
2
0
(Section
5.2) is updated.
1
0
1
0
0
0
0
0
MPR03X
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