topic Looking for documentation on "passive filter" function of GPIO's on KL03 in Kinetis Microcontrollers

Looking for documentation on "passive filter" function of GPIO's on KL03

andrewsterianap — Sun, 03 Jan 2016 06:45:15 GMT

The reference manual says "Refer to the device data sheet for filter characteristics.", but the device data sheet does not have the word "passive" anywhere.

I've seen a similar question asked about the KL25 but the "correct answer" for that thread simply says "This filter is not the traditional filter. It is not high frequencty filter nor band filter. It can looks like a pulse counter. It will delete small width pulse. So it looks like a filter."

I'm really hoping for more information here, preferably with actual numbers!

Re: Looking for documentation on "passive filter" function of GPIO's on KL03

PitOn — Sun, 03 Jan 2016 11:17:16 GMT

Hi.

majorization filter

example

input port three samples "101"
two 1, one 0. -> out 1 (dominates)

input port 3 sample 001

two 0, one 1. -> out 0 (dominates)

Majorization - Wikipedia, the free encyclopedia

Re: Looking for documentation on "passive filter" function of GPIO's on KL03

andrewsterianap — Sun, 03 Jan 2016 19:24:40 GMT

Thanks...is this documented anywhere in the NXP/Freescale docs? Does this imply there is a 3-clock-cycle delay in reading the GPIO pin?

Re: Looking for documentation on "passive filter" function of GPIO's on KL03

jeremyzhou — Mon, 04 Jan 2016 06:03:21 GMT

Hi,

This filter (Passive filter) is not the traditional filter. It is not high frequency filter nor band filter. It is a analog low pass filter (10 MHz to 30 MHz bandwidth). Passive filter deals with analog signals and using to filter high frequency noise, the frequency more than 30MHz signal will be filtered. Passive filter frequency is fixed and could not be modified.

Have a great day!

Ping

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Re: Looking for documentation on "passive filter" function of GPIO's on KL03

andrewsterianap — Mon, 04 Jan 2016 17:42:09 GMT

Thanks Ping. So it looks like there is just a 10-30 MHz low-pass filter on the pin. Do you know if there is any delay in reading the pin, recognizing edge-triggered interrupts, etc. due to this filtering?

Re: Looking for documentation on "passive filter" function of GPIO's on KL03

jeremyzhou — Tue, 05 Jan 2016 02:25:25 GMT

Hi Andrew,

Sorry, I don't find any descriptions about the delay of the passive filter.

I think it doesn't matter.
Have a great day,
Ping