query regarding capsense : False detection

rahulpatel · ‎May 06, 2021

Hi,

I am using Capsens module V4.0.

I am using Widget Buttons for my application In this, I found that sometimes it detects the false senses means it sens when I do not even touch the button..

In my application I use Enable all 13 buttons using CapSense_SetParam(CapSense_WDGT_ENABLE0_PARAM_ID, 8191); and after complete the process I disable only 12 buttons CapSense_SetParam(CapSense_WDGT_ENABLE0_PARAM_ID, 4096); because I use the 13th button for touch detection only this performs at every operation.

Why this false detection is happening? is it because of the calling CapSense_SetParam(CapSense_WDGT_ENABLE0_PARAM_ID, 8191) ?

Hari · ‎May 06, 2021

Hi @rahulpatel,

Sure, I can help you with manual tuning. Please note that the easiest way to get started with manual tuning is to use smartsense for the hardware parameters (such as resolution, sense clock frequency, etc) and then copy the same to manual tuning parameters.

But the actual procedure is to

1. Determine the parasitic capacitance (Cp) of the sensor using BIST (CapSense configurator > Advanced tab > General Tab > Enable self test library) and use CapSense_GetSensorCapacitance API that returns the Cp in femtoFarads.

2. Then, set sense clock frequency such that Fsw < 1/(10*R*Cp), where R is 500(internal) + 560(external) = 1k.

3. It is recommended to leave IDAC autocalibration and compensation IDAC on. Set any initial resolution and then launch tuner. Go to SNR tab. Make sure that the SNR is at least 5:1. If lower, you can increase the resolution till you obtain 5:1 SNR.

4. Then, set the firmware parameters based on the signal that you see in SNR window.

Do let me know if there are any queries.

Best regards,
Hari

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query regarding capsense : False detection

query regarding capsense : False detection

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