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MPR121
Sensors
16
Freescale Semiconductor, Inc.
5.11
Electrode Configuration Register (ECR, 0x5E)
The Electrode Configuration Register (ECR) determines if the MPR121 is in Run Mode or Stop Mode, controls the baseline
tracking operation and specifies the input configurations of the 13 channels.
The ECR reset default value is 0x00, which means MPR121 is in Stop Mode without capacitance measurement on all
13 channels. Setting ELEPROX_EN and/or ELE_EN control bits to non-zero data will put the MPR121 into Run Mode. This will
cause the MPR121 to operate immediately on its own. Clearing the ELEPROX_EN and ELE_EN all to zeros will set the MPR121
into Stop Mode (which is its lowest power state). The MPR121 can be switched between Stop Mode and Run Mode at anytime
by configuring the ECR.
If all channels including the13th proximity detection channel are enabled, the proximity sensing channel is scanned first, followed
by ELE0, ELE1..., and ELE11 respectively. The scan runs periodically at the sampling rate specified by the ESI in the Filter/CDT
Configuration Register (0x5D). Refer to the table above for configuration of the different channels. Enabling specific channels will
save the scan time and sensing field power spent on the unused channels.
In a typical touch detection application, baseline tracking is enabled. This is to compensate for the environment and background
induced slow capacitance change to the input sensing channels. The CL bits can enable/disable the baseline tracking and specify
how to load the baseline initial values. Since the baseline tracking filtering system has a very large time constant and the initial
Electrode Configuration Register (0x5E)
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Read
CL
ELEPROX_EN
ELE_EN
Write
Table 9. Bit Descriptions
Field
Description
CL
Calibration Lock - Controls the baseline tracking and how the baseline initial value is loaded
00 - Baseline tracking enabled, initial baseline value is current value in baseline value register
(Default)
01 - Baseline tracking is disabled
10 - Baseline tracking enabled, initial baseline value is loaded with the 5 high bits of the first
10-bit electrode data value
11 - Baseline tracking enabled, initial baseline value is loaded with all 10 bits of the first
electrode data value
ELEPROX_EN
Proximity Enable - Controls the operation of 13th Proximity Detection
00 - Proximity Detection is disabled (Default)
01 - Run Mode with ELE0~ELE1 combined for proximity detection enabled
10 - Run Mode with ELE0~ELE3 combined for proximity detection enabled
11 - Run Mode with ELE0~ELE11combined for proximity detection enabled
ELE_EN
Electrode Enable - Controls the operation of 12 electrodes detection
0000 - Electrode detection is disabled (Default)
0001 - Run Mode with ELE0 for electrode detection enabled
0010 - Run Mode with ELE0~ ELE1 for electrode detection enabled
0011 - Run Mode with ELE0~ ELE2 for electrode detection enabled
0100 - Run Mode with ELE0~ ELE3 for electrode detection enabled
0101 - Run Mode with ELE0~ ELE4 for electrode detection enabled
0110 - Run Mode with ELE0~ ELE5 for electrode detection enabled
0111 - Run Mode with ELE0~ ELE6 for electrode detection enabled
1000 - Run Mode with ELE0~ ELE7 for electrode detection enabled
1001 - Run Mode with ELE0~ ELE8 for electrode detection enabled
1010 - Run Mode with ELE0~ ELE9 for electrode detection enabled
1011 - Run Mode with ELE0~ ELE10 for electrode detection enabled
11xx - Run Mode with ELE0~ ELE11 for electrode detection enabled