Trouble getting CapSense to start the same each time at power up

[Doorknob]

I am doing a project that uses 5 capsense buttons to operate a locking mechanism in my project. I m having issues that when i power up the unit by placing batteries into the unit it some times does not operate properly.  There are times I only get 4 buttons to work or I get only one button to work.  Most the time is does work properly were all 5 buttons work great. In the design i am using the shield option and activated sense my project will be around water a significant amount of time.

CapSense Setup:

I have a 2.2nF cap on the Cmos pin and a 10nF cap on the Csh pin.

Board:

The board is a four layer board in which i followed the guidelines suggested in getting started with capsense. i followed the guidelines in AN85951 page 110.

Top layer: Hatch fill 7-mill and 45-mil grid ... connected to shield.

Layer-2: Hatch fill 7-mill and 70-mill grid ... connected to shield.

Layer 3: Solid Plane ... connected to Gnd

Bottom Layer: Hatch fill 7-mill and 70-mill grid ... connected to Gnd

I have attached my project for review.

I was hoping i could get some help as to why my capsense is not working constantly all the time at power.  I my board is need for review let me know and i will post it if necessary.

Thanks

Scott

[Doorknob]

Woops i did not attach my porject ... ! !

[Hari · Accepted solution]

Hello ScCl_3419596​

Can you please attach a video demonstrating the issue that is explained? Are you facing it only if you press the button while power up?

Is the issue present even after power up or do the buttons start working after some time?

Can you use BIST (the self test library, requires manual tuning to be enabled) to check the parasitic capacitance of the sensor?

You can then use CapSense_GetSensorCapacitance for measuring the parasitic capacitance of the sensor.

Please make sure that Cp is greater than 5pF and less than 45pF for all sensors.

You can also try manual tuning by setting the parameters obtained from smartsense while the system is working. This way, the sensors will take the best configuration irrespective of the conditions while power up.

Best regards

Hari