MPR121_10 FREESCALE [Freescale Semiconductor, Inc], MPR121_10 Datasheet - Page 52

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

MPR121
52
Section C
Section D
Register Address
Register Address
0x4C
0x4D
0x5D
0x4A
0x4B
0x4E
0x4F
0x41
0x42
0x43
0x44
0x45
0x46
0x47
0x48
0x49
0x50
0x51
0x52
0x53
0x54
0x55
0x56
0x57
0x58
Description: The touch threshold registers set the minimum delta from the baseline when a touch is detected
Description: There are three settings embedded in this register so it is only necessary to pay attention to one.
Variation: For very small electrodes, smaller values can be used and for very large electrodes the reverse is
Variation: To save power, the 1 ms can be increased to 128 ms by increasing the setting to 0x07. The values
ELE0 Touch Threshold
ELE0 Release Threshold
ELE1 Touch Threshold
ELE1 Release Threshold
ELE2 Touch Threshold
ELE2 Release Threshold
ELE3 Touch Threshold
ELE3 Release Threshold
ELE4 Touch Threshold
ELE4 Release Threshold
ELE5 Touch Threshold
ELE5 Release Threshold
ELE6 Touch Threshold
ELE6 Release Threshold
ELE7 Touch Threshold
ELE7 Release Threshold
ELE8 Touch Threshold
ELE8 Release Threshold
ELE9 Touch Threshold
ELE9 Release Threshold
ELE10 Touch Threshold
ELE10 Release Threshold
ELE11 Touch Threshold
ELE11 Release Threshold
0x0F or 15 in decimal is an estimate of the minimum value for touch. Most electrodes will work with
this value even if they vary greatly in size and shape. The value of 0x0A or 10 is the release threshold
register allowed for hysteresis in the touch detection.
true. One easy method is to view the deltas actually seen in a system and set the touch at 80% and
release at 70% of delta for good performance.
Filter Configuration
The ESI controls the sample rate of the device. In the default, the setting used is 0x00 for 1 ms
sample rate. Since the SFI is set to 00, resulting in 4 samples averaged, the response time will be
4 ms.
are base 2 exponential thus 0x01 = 2 ms; 0x02 = 4 ms; and so on to 0x07 = 128 ms. Most of the
time, 0x04 results in the best compromise between power consumption and response time.
Register Name
Register Name
Value
Value
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x0F
0x0A
0x04
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Application Note
Application Note
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