Touch Tuning based on KE15Z Help Needed

arun07 — Mon, 02 Nov 2020 14:44:19 GMT

Hello Everyone,

I am new to the Kinetis Series of Micro-controller and I am using MKE15Z micro-controller for the touch-based project, all of my keys are configured as self-capacitance electrodes.

I used the touch_sensing example from the SDK and modified it to suit my needs. And here is the visualization on one of the electrodes..

Now I am in the phase of tuning the touch parameters, but to start it looks complicated to me, although I am taking reference from the touch manual to help me get started.

In this case (shown above), the dead-band signal and the predicted signal are very close, this means that I have to reduce it? or there is a way I can increase the gain of the predicted signal.

I checked the examples and found that usually the dead-band signal is kept 600+baseline level, in my case I have just put this value to 400.

When I touch the Electrode, the response is very slow, and when is release the Electrode, the response is even slower.

I have used a LED, which gets turned on when Electrode is press and off when Electrode is released.

How to prevent this?

const struct nt_electrode El_1 = {
 .shielding_electrode = NULL,
 .multiplier = 0,
 .divider = 0,
 .shield_threshold = 5,
 .shield_gain = 30,
 .shield_attn = 1,
 .shield_sens = 800,
 .keydetector_params.usafa = &nt_keydetector_usafa_El_1,
 .keydetector_interface = &nt_keydetector_usafa_interface,
 .pin_input = 2,
 .gpio_input = GPIO_PTE10,
 .baseline_level = 36363,
};‍‍‍‍‍‍‍‍‍‍‍‍‍‍

const struct nt_keydetector_usafa nt_keydetector_usafa_El_1 = {
 .signal_filter.coef1 = 2,
 .base_avrg.n2_order = 12,
 .non_activity_avrg.n2_order = 15,
 .entry_event_cnt = 4,
 .deadband_cnt = 4,
 .signal_to_noise_ratio = 2,
 .min_noise_limit = 200,
 .dc_track_enabled = 1,
 .dc_track_cnt = 100,
};‍‍‍‍‍‍‍‍‍‍‍

Another problem is with FreeMASTER, every time I have to change the colors of the signal as they are reverted back to black color always (FreeMASTER Version 3.0.2.6)

So, to summarize I want to know if there is a document, which can help me in tuning the touch parameters for my board.

Any webinar, tutorial, document link will be extremely helpful.

Thanks in advance.

Re: Touch Tuning based on KE15Z Help Needed

FelipeGarcia — Fri, 08 May 2020 16:20:18 GMT

Hello Arun,

I don’t know if you have already checked our NXP Touch Development guide. Here you will find a lot of configuration and description about our touch library.

Have a great day,
Felipe

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Touch Tuning based on KE15Z Help Needed

Re: Touch Tuning based on KE15Z Help Needed