KITMPR121EVM Freescale Semiconductor, KITMPR121EVM Datasheet - Page 38

• Manufacturer Part Number: KITMPR121EVM
• Description: KIT EVALUATION MPR121
• Manufacturer: Freescale Semiconductor

Specifications of KITMPR121EVM

• Sensor Type: Proximity
• Interface: USB
• Voltage - Supply: 5V, USB
• Embedded: No
• Utilized Ic / Part: MPR121
• Interface Type: USB, I2C, SCI, SPI
• Operating Voltage: 3.3 V
• Data Bus Width: 8 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sensitivity: -
• Sensing Range: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: MPR121, MC9S08QG8

MPR121
38
and actual Data changes. To understand how the Baseline can change, refer to AN3891.
DEBOUNCE TOUCH AND RELEASE REGISTER
releases by further improving the performance. The debounce allows two different settings to prevent bounce in the end system.
If the value is set to 0x22, the requirement would be three sequential changes in status before the change would be recognized.
CONCLUSION
utilizing the two threshold settings. Thus the provided hysteresis prevent Jitter on the data from going through the to the output
Depending on environmental conditions, the Debounce can be used to eliminate the remainder of dramatic change of the signal
that aren’t really touches.
AN3890.
For the system to recognize a touch the delta must be greater than the Touch Threshold.
A release is triggered when the Delta falls below the Release Threshold. This can happen for both changes to the Baseline
The last register available in this set is the Debounce register. The Debounce register maintains the accuracy of touch and
The use of each of the features together can have a great effect of the jitter and false couch rejection. Jitter is prevented by
Additional filtering can be done before the data gets to the touch detection system. Refer to Freescale Application Note
Table 33. Debounce Touch and Release Register Field Descriptions
Reset:
Field
6:4
DR
2:0
DT
W
R
7
0
0
Debounce Release – The Debounce Release determines the number of sequential
release detections before an interrupt is triggered and a release is reported.
000 Encoding 0 - Consecutive releases detection before Status change is 1
001 Encoding 1 - Consecutive releases detection before Status change is 2
~
007 Encoding 7 - Consecutive releases detection before Status change is 8
Debounce Touch – The Debounce Touch determines the number of sequential touch
detections before an interrupt is triggered and a touch is reported.
000 Encoding 0 - Consecutive touch detection before Status change is 1
001 Encoding 1 - Consecutive touch detection before Status change is 2
~
007 Encoding 7 - Consecutive touch detection before Status change is 8
= Unimplemented
Figure 45. Debounce Touch and Release Register
Trigger Release
6
0
Trigger Touch
DR
Delta = Baseline - Data
5
0
→
→
Delta > Touch Threshold
Delta < Touch Threshold
4
0
Description
3
0
0
2
0
Dt
1
0
Freescale Semiconductor
0
0
Sensors