TSI Automatic Noise Mode

[amitmehta]

I am trying to configure TSI in auto noise mode to avoid EMI/EMC noise, but i am little bit confuse with parameters which need to be configure to avoid maximum noise. If there is any reference code or document apart from KL16 reference manual i would be good.

[jingpan]

Hi Amit,

I can't find any examples exactly meet your need. You can find some useful documents and tools here:

https://www.nxp.com/products/sensors/other-sensors/touch-sensors/touch-sensing-software:TSS?tab=Docu...

Below is a touch electrodes design guide

https://www.nxp.com/docs/en/application-note/AN3863.pdf 

Regards,

Jing

[amitmehta]

Hi Jing,

So i had configured TSI module with below configurations

tsiConfig.prescaler = kTSI_ElecOscPrescaler_8div;
tsiConfig.refchrg = kTSI_RefOscChargeCurrent_64uA;
tsiConfig.nscn = kTSI_ConsecutiveScansNumber_18time;

tsiConfig.mode = kTSI_AnalogModeSel_AutoNoise;
tsiConfig.extchrg = kTSI_ExtOscChargeCurrent_500nA;
tsiConfig.dvolt = kTSI_OscVolRailsOption_1;


tsiConfig.thresh = 0U;
tsiConfig.thresl = 0U;

and i am scanning electrodes one by one every 10ms and delta value i have set is 2500.

initially system run normally but after longer duration sensitivity of cap touch input increase to extent that without even touching the point i am able to get a valid touch input from a distance of round about 1cm.

Can you help me why this issue might be there.

[jingpan]

Hi,

I checked your setting on my frdm board. I found it is unstable really. But  there is rarely docs or codes about noise mode. I heard from FAE that noise mode is not recommended. Normal mode and TSS library are recommended.

Regards,

Jing

[amitmehta]

Hi Jing,

Basically we have connected an external overlay to KL16 controller to detect touch input. So earlier i have configured controller in normal mode but when the system was subject to RF immunity test, controller was detecting touch input, so to over come that issue i have to configure it in auto noise mode as it is designed for EMC noise, so during test there was no issue, but in longer run under normal condition system starts detecting touch from a distance.

[jingpan]

Hi Amit,

NXP has a TSS library

https://www.nxp.com/products/sensors/other-sensors/touch-sensors/touch-sensing-software:TSS

This library include KL26 project. As you know KL16 has same evaluation board with KL26.  This project support Noise Detect Mode. You can enable this function in TSS_SystemSetupGlobal.h. You can select if sensitivity autocalibration is used by  TSS_USE_AUTO_SENS_CALIBRATION macro for whole demo. Freemaster is also added to this project so that you can observe the sensor parameter change directly. Hope this can give you some help.

Regards,

Jing

[jingpan]

Hi Amit,

you can find examples in SDK package SDK_2.2_FRDM-KL26Z\boards\frdmkl26z\driver_examples\tsi_v4.

You also can download TSI software develop kit from https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/kinetis-c....

Regards,

Jing

[amitmehta]

Hi Jing,

In SDK_2.2 there are example related to normal working mode but not related to autonoise mode and what is significance of configuration on touch input response.