Data Sheet

MPR121 Sensor
17 Freescale Semiconductor
Auto Configuration Register 0 (0x7B)
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Read
AFES
RETRY
BVA
ARE
ACE
Write
ACE: 1: Enable AUTO-CONFIG, 0: Disable AUTO-CONFIG
ARE: 1: Enable AUTO-RECONFIG, 0: Disable AUTO-RECONFIG
BVA: Baseline Value Adjust Control specifies how to change baseline value for each channel upon finishing auto
configuration and auto re-configuration.
00: Baseline value is no change,
01: Baseline value is cleared to zero,
10: Baseline is set to the AUTO-CONFIG baseline value with 5MSBs loaded and the other lower bits cleared,
11: Baseline is set to the AUTO-CONFIG baseline value
RETRY: MPR121 may retry AUTO-CONFIG or AUTO-RECONFIG after failed.
00: no retry,
01: 2 times,
10: 4 times,
11: 8 times.
AFES: This bit specifies AFE Samples during binary search. The AFES values should be as same as global AFES in ACR
register, otherwise AUTO-CONFIG couldn’t configure CDCx/CDTx correctly.
00: 6 samples,
01: 10 samples,
10: 18 samples,
11: 34 samples.
Auto Configuration Register 1 (0x7C)
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Read
SCTS
0
0
0
0
OORIE
ARFIE
ACFIE
Write
SCTS: 1: Skip Charge Time Search during binary search. User should specify charge time through global value CDT or
individual value CDTx in respective registers. 0: Charge Time Search is executed during binary search.
ACFIE: 1: AUTO-CONFIG Fail Interrupt Enable, 0: AUTO-CONFIG Fail will not cause interrupt.
ARFIE: 1: AUTO-RECONFIG Fail Interrupt Enable, 0: AUTO-RECONFIG fail will not cause interrupt.
OORIE: 1: Out of Range Interrupt Enable, 0: Out of Range error will not cause Interrupt.
13. Out Of Range Status Registers (0x02, 0x03)
MPR121 checks electrode data after AUTO-CONFIG/AUTO-RECONFIG operation and also in normal measurement. When
electrode data goes out of a range, corresponding OORx bits in the OOR0 and OOR1 Registers become "1" to indicate failed
electrode. One possible example of triggering OOR error may be caused by shorting one of the measurement channels to
ground. The valid range can be programmed through USL Register and LSL Register. Those bits are cleared when passed
AUTO-CONFIG, AUTO-RECONFIG or range check. These two register is read only, user can’t change the contents.
OUT OF RANGE Register 0 (0x02)
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Read
OOR7
OOR6
OOR5
OOR4
OOR3
OOR2
OOR1
OOR0
Write
OUT OF RANGE Register 1 (0x03)
Read
ACFF
ARFF
0
OOR12
OOR11
OOR10
OOR9
OOR8
Write
OORx: 1: OOR error detected on respective channel, 0: No OOR error.
ACFF: AUTO-CONFIG Fail Flag. When AUTO-CONFIG failed, this bit set.
ARFF: AUTO-RECONFIG Fail Flag. When AUTO-RECONFIG failed this bit set.