MPR121_10 FREESCALE [Freescale Semiconductor, Inc], MPR121_10 Datasheet - Page 39

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

Sensors
Freescale Semiconductor
AN3893: MPR121 Proximity Detection
INTRODUCTION
device. Like MPR03x, MPR121 has a unique feature that all the electrode inputs can be internally connected together so that all
the surface touch sensing area on the inputs are “summed” together to act as a single large electrode pad. This can effectively
increase the total area of the sensing conductor for non-contact near proximity detection for hand approaching.
OVERVIEW
be used as contactless proximity detection as well as finger touch detection if each sensing pad is designed properly and relevant
register are set properly.
proximity detection. On the other side, it’s true that in most portable application design there is no dedicated big surface area left
for proximity detection as the touch sensing buttons occupy all the available surface area. To make proximity detection at the
same time of touch detection without additional dedicated large sensing pad, MPR121 has an internal input multiplexor which
can connect all input sensing channels together so that all the touch sensing surface areas on the input pads are “summed”
together effectively acting as a single large sensing pad.
of all the pads can also used for proximity detection (e.g., hand approaching).
PROXIMITY DETECTION REGISTER SETTING
tions, other than that, all the concepts applied to the proximity detection are the same as touch sensing detection.
1.0
Table
sensing detect sequence. Once configured, we refer to this area detection as the 13th Proximity Detection electrode.
2.0
13
Table 34. Electrode Configuration Register 0x5E (Reset Default: 0x00)
Table 35. Eleprox Electrode Register 0x1C, 0x2D (Reset Default: 0x00, 0x00)
th
MPR121 is a feature rich, second generation touch sensor controller after Freescale’s initial release of the MPR03x series
Capacitive proximity detection uses the same principle as capacitive touch sensing. Each MPR121 input sensing channel can
Typically a smaller pad size is used for finger touch button detection; while a larger pad size is necessary for contactless near
Using this scheme in typical applications, the 12 channels can be used for 12 key buttons touch sensing, and the surface area
Like each independent touch sensing detection, the 13th Proximity Detection electrode also has its own register configura-
Proximity detection (a/k/a area detection mode) is enabled by configuring the Electrode Configuration Register (0x5E), see
AD1
Eleprox Electrode Registers (0x1C, 0x2D) contain the 10-bit raw data of the capacitance-voltage measurement value for the
Reset
Read
Write
0
1
1
0x1C
0x1D
Proximity Detection electrode.
Bit
34. In MPR121, this adds an area detection step (the 13
Enable Proximity Sensing
Proximity Data Register and Baseline Register
AD0
1
0
1
CL[1]
Bit7
Bit7
Bit7
D7
—
0
EC3
x
x
x
EC2
CL[0]
x
x
x
Bit6
Bit6
Bit6
D6
—
0
EC1
x
x
x
AD[1]
Bit5
Bit5
Bit5
D5
—
0
EC0
x
x
x
AD[0]
Bit4
Bit4
Bit4
D4
—
th
0
pseudo Electrode) before all the independent electrodes touch
Area Detection by connecting ELE0~11.
Area Detection by connecting ELE0~1.
Area Detection by connecting ELE0~3.
EC[3]
Bit3
Bit3
Bit3
D3
—
0
Description
EC[2]
Bit2
Bit2
Bit2
D2
—
0
EC[1]
Bit1
Bit1
Bit1
D1
D9
0
EC[0]
Bit0
Bit0
Bit0
MPR121
D0
D8
0
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