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CAPSENSE™ & MagSense

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I am working on a project in which I am using this IC "cy8cmbr3108-lqxit",  for the touch sensing.

I am facing issue with the touch sensing.

I am using EZ-Click for making the device configurations and using the API's provided by the Cypress for programming the Touch IC, but still device is not sensing the touch.

When I check with DSO in the Touch Pins I am seeing some voltage of 240 mV and not seeing any pulse which is configured at 60ms rate.

I had checked the communication and it is working fine but I am not able to debug the issue.

If someone can help, that will be great.

Added Schematic for the reference and I am using stm32 for controlling the touch IC.TouchIC.png



Vaibhav Bansal

1 Solution
Moderator 250 sign-ins 250 replies posted 100 solutions authored

Hi @Vaibhav_Bansal,

Schematic pointers:
>560ohm series resistors must be used for CapSense pins- this includes CSx, PSx, SLDx, GUARD, and SH pins
>VDD and VDDIO pins need to have the decoupling capacitors (1uF and 0.1uF) connected separately (so a pair consisting of 1uF and 0.1uF needs to be connected from VDD to GND, and another pair from VDDIO to GND). They cannot be combined as done in the schematic.
>330ohm series resistors and 4.7kohm pull-up resistors have to be used for I2C lines.
>A suitable pull-up resistor is to be used for HI pin based on the interface voltage.
>Unused CS pins have to be connected to GND.
>Unused GPO pins: if GPO drive mode is "open drain low", then connect it to GND;
                                         if GPO drive mode is "strong", then leave it as it is.


The issue might be the tuning for the sensors. Refer to chapter 6 of the CY8CMBR3xxx Capsense Design Guide for detailed steps to tune your sensors.

> Ensure a minimum SNR of 5:1 (section 6.2.1)
> Tune the sensitivity of the sensor such that a sufficient signal is received. Based on this, the finger threshold, hysteresis, noise threshold, negative noise threshold, and low-baseline reset must be set. (section 6.2.2 and 6.2.3)

Hope this helps.


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