MPR121_10 FREESCALE [Freescale Semiconductor, Inc], MPR121_10 Datasheet - Page 46

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

MPR121
46
these four register is 0x00. When a GPIO is programmed as output and the DAT register is “1” and if the corresponding PWM_
[3:0] register is not zero, the GPIO pin outputs PWM waveform. The PWM period is fixed 8ms (1/256 of 32 KHz OSC) and PWM_
[3:0] register decides duty of the waveform.
a mixed duty cycle would be possible to occur.
Therefore, when interval time (=Touch Detection Sample Interval) is close to measurement time (depends on charge time, AFE
Samples and number of measurement electrodes), the PWM operation is disturbed and the waveform couldn’t keep programmed
duty.
PWM0[3:0] ~ PWM7[3:0] is used to set the PWM duty of GPIO0 ~ GPIO7 respectively. The power up reset default setting for
These register can be read/write any time, even if MPR121 is in Run Mode. When the register changes during PWM enables,
The PWM duty is not so much accurate, because GPIO output transition (include PWM) inhibits during measurement state.
PWM_ [3:0]
15
—
0
1
2
PWM is off, GPIO outputs stable high when DAT register is “1”
GPIO output duty is 1:15 (mostly output low)
GPIO output duty is 2:14 (mostly output low)
—
GPIO output duty is 15:1 (mostly output high)
Description (_ is 0~7)
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