MPR121 datasheet(44/57 Pages) FREESCALE

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MPR121

Sensors

Freescale Semiconductor

Figure 47. Configuration 2: MPR121 runs from a 2.5 V to 3.6 V supply.

These registers control GPIO function. D7~D0 bits corresponds GPIO7~GPIO0 pins respectively. The GPIO control registers

can write always regardless Shutdown and Run mode.

EN[7:0], DIR[7:0], CTL0[7:0], CTL1[7:0]: Configuration Register

The number of touch sensing electrodes (and therefore the number of GPIO ports available) is configured by the Electrode

Configuration register (0x5E) and GPIO Enable Register (0x77), but electrode configuration has higher priority than GPIO fea-

ture. When a pin is enabled as GPIO but is also selected as electrode by Electrode Configuration Register, the GPIO function is

disabled immediately and it becomes an electrode during Run mode. But all 8 ports automatically become GPIO ports in Shut-

down mode because none of the ports are being enabled as touch electrodes in Shutdown mode.

During the shutdown mode just after power on reset, all 8 GPIO ports are in high impedance as all the GPIO ports are default

disabled. Take care to program unused ports which are not going to be used as either touch electrodes or GPIO to avoid floating

inputs or outputs shorted to a rail. One approach is to enable unused ports to be GPIO inputs with internal pull-up or pull-down.

Table 44. GPIO Control Registers

Name

Address

GPIO Control 0

0x73

CTL0[7]

CTL0[6]

CTL0[5]

CTL0[4]

CTL0[3]

CTL0[2]

CTL0[1]

CTL0[0]

GPIO Control 1

0x74

CTL1[7]

CTL1[6]

CTL1[5]

CTL1[4]

CTL1[3]

CTL1[2]

CTL1[1]

CTL1[0]

GPIO Data

0x75

DAT[7]

DAT[6]

DAT[5]

DAT[4]

DAT[3]

DAT[2]

DAT[1]

DAT[0]

GPIO Direction

0x76

DIR[7]

DIR[6]

DIR[5]

DIR[4]

DIR[3]

DIR[2]

DIR[1]

DIR[0]

GPIO Enable

0x77

EN[7]

EN[6]

EN[5]

EN[4]

EN[3]

EN[2]

EN[1]

EN[0]

GPIO Data Set

0x78

SET[7]

SET[6]

SET[5]

SET[4]

SET[3]

SET[2]

SET[1]

SET[0]

GPIO Data Clear

0x79

CLR[7]

CLR[6]

CLR[5]

CLR[4]

CLR[3]

CLR[2]

CLR[1]

CLR[0]

GPIO Data Toggle

0x7A

TOG[7]

TOG[6]

TOG[5]

TOG[4]

TOG[3]

TOG[2]

TOG[1]

TOG[0]

VDD

ELE11/LED7

GND

0.1

μF

75 k

Ω 1%

2.5 V to 3.6 V

VDD

2.5 V to 3.6 V

VSS

VREG

IRQ

SCL

SDA

ADDR

REXT

ELE10/LED6

ELE9/LED5

ELE8/LED4

ELE7/LED3

ELE6/LED2

ELE5/LED1

ELE4/LED0

ELE3

ELE2

ELE1

ELE0

MPR121Q

TOUCH SENSOR

GND

0.1

μF

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