MPR121 datasheet(45/57 Pages) FREESCALE

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MPR121

Sensors

Freescale Semiconductor

The GPIO system allows the GPIO pins to be set as input or output. When an EN bit sets, the corresponding GPIO pin is

enabled and the function is configured by CTL0, CTL1 and DIR bits. When the port is used as input, it can be configured as normal

input or with additional internal pull-down or pull-up for input port. For output configuration, it can be push/pull or open drain.

DAT[7:0]: Data Register

When a GPIO is as output, the GPIO port outputs the bit level of this register. The output level toggle holds on any electrode

charging and AD conversion and the level transition will be occurred after the AD conversion. Reading this register returns the

content of the DAT register (not a level of the port).

When a GPIO is as input, reading this register returns latched input level of the corresponding port (not contents of the DAT

SET[7:0]: Set Data Register

Writing a “1” to bits in this register will set them in the Data Register.

CLR[7:0]: Clear Data Register

Writing a “1” to bits in this register will clear them in the Data Register.

TOG[7:0]: Toggle Data Register

Write a bit with “1” to the GPIO Data Set Register, GPIO Data Clear Register, and GPIO Toggle Register set/clear/toggle con-

tents of the corresponding DAT bit. Write “0” has no meaning. Using of those registers allows any individual port(s) to be able

individually set, cleared, or toggled without affecting other ports. Reading those register returns as same as DAT register reading.

LED DRIVER

Each GPIO pin has LED driver capability which can source up to 12 mA. When GPIO is used to driver LED, connect the GPIO

output to an LED forward biased with its cathode to GND so that GPIO output high lights the LED. Place a current limiting resistor

is series with LED to limit the current below 12 mA (refer to the typical application circuit).

When LED dimming control is needed, the PWM control register can be set to get the desired dimming control. Alternatively,

the PWM can also be used to drive the beeper.

DIR

CTL[0:1]

DESCRIPTION

GPIO function is disabled. Port is high-z state.

GPIO port becomes input port.

GPIO port becomes input port with internal pull-down.

GPIO port becomes input port with internal pull-up.

Not defined yet (as same as CTL = 00).

GPIO port becomes CMOS output port.

GPIO port becomes high side only open drain output port for LED driver.

GPIO port becomes low side only open drain output port.

Not defined yet (as same as CTL = 00).

Table 45. PWM_[3:0}: PWM Duty Control Registers

Name

Address

PWM 0

0x81

PWM1[3]

PWM1[2]

PWM1[1]

PWM1[0]

PWM0[3]

PWM0[2]

PWM0[1]

PWM0[0]

PWM 1

0x82

PWM3[3]

PWM3[2]

PWM3[1]

PWM3[0]

PWM2[3]

PWM2[2]

PWM2[1]

PWM2[0]

PWM 2

0x83

PWM5[3]

PWM5[2]

PWM5[1]

PWM5[0]

PWM4[3]

PWM4[2]

PWM4[1]

PWM4[0]

PWM 3

0x84

PWM7[3]

PWM7[2]

PWM7[1]

PWM7[0]

PWM6[3]

PWM6[2]

PWM6[1]

PWM6[0]

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