topic Re: Push Button Bounce in Kinetis Software Development Kit

Push Button Bounce

shauldorf — Wed, 06 Jan 2016 20:24:43 GMT

I’m using FRDM-K64F with push button as a source for external interrupt.

How switch bounce can be cleaned using KDS3.0 + KSDK1.2.0

Re: Push Button Bounce

DavidS — Thu, 07 Jan 2016 21:25:15 GMT

Hi Shaul,

Try enabling the PFE bit in the PORTx_PCRn register:

PFE = Passive Filter Enable

Passive filter configuration is valid in all digital pin muxing modes.

0 Passive input filter is disabled on the corresponding pin.

1 Passive input filter is enabled on the corresponding pin, if the pin is configured as a digital input. Refer

to the device data sheet for filter characteristics.

Regards,

David

Re: Push Button Bounce

shauldorf — Fri, 08 Jan 2016 21:41:42 GMT

Hello David and Thanks

I don’t know if using PE I can configure PORTxPCRn register.

In my application I’m using two PortA inputs PTA1 & PTA2

To solve yours suggestion and I tried to use Pins1:PinSetting option.

There was no improvement in SW bouncing reduction.

I’m attaching my configuration.

I think that my configuration is wrong, using debugger I have seen that “PFE” remains low.

I think that using assembly can solve the problem but I don’t know how to do this (I have hardware experience).

Do you have any recommendations.

Thanks

Shaul

Using low pass filter (RC) at input solves the problem but I prefer software solution.

Re: Push Button Bounce

DavidS — Fri, 08 Jan 2016 23:15:41 GMT

Hi Shauk,

Two suggestions....use an interrupt on the PTA1/2 GPIO pins and in the interrupt have a delay loop. After delay loop if the signal is still asserted, then assume debounced and proceed. If signal was de-asserted then take not action. Positive is simple to implement. Negative it wastes time during debounce.

Other suggestion for K64 is to use a PORT D pin that has a digital filter capability and you can use hardware to do your debouncing.

Chapter 10 tells you that only PORT D pins have digital filter capability.

Chapter 11 has the "Digital Filter" registers for PORTD (PORTD_[DFER&DFCR&DFWR] to configure.

The fsl_port_hal.h has the MACRO's to access this stuff. Ex: static inline void PORT_HAL_SetDigitalFilterWidth(PORT_Type * base, uint8_t width)

Regards,

David

Re: Push Button Bounce

shauldorf — Sun, 10 Jan 2016 21:59:15 GMT

Hello David

Thanks :smileyhappy:

Your guidance was excellent.

Two solutions have been tested and are working.

Shaul