CY8C20434 used for sensor keypad. Sensor hanging up.

[RaRu_1223526]

I have an issue with CY8C20434 used for sensor keypad with 12 sensors ( 0 - 9 , Enter, correct).

I'm using csa user module for sensoring.

Everything works fine untill I push two or three fingers onto keypad with high pressure for 4 or 5 seconds e.g.

After that most of the sensors are still working but certain sensors (mostly key 3 and key 6) are not working any more.

After power off/power on all sensors work fine again. I can reproduce the effect.

Parameter "sensors Autoreset" is enabled. So actually the sensors should work after pushing a key for long time.

Is that issue known? Do you suggest to use other module like CSD or SmartSense?

Best regards

Rainer

[SampathS_11]

Hello Rainer,

Can you kindly let us examine your project? Also do kindly include a photo of the sensor PCB. Can you kindly give us some numbers of "high pressure"?

Can you observe the same error with the sensor PCB mounted, and the sensor PCB unmounted?

Best regards,

Sampath Selvaraj

[RaRu_1223526]

Hi,

attached please find the project and photos of the pcb front without keyboard sheet fixed, pcb back and pcb front with keyboard sheet fixed.

The sheet is fixed by glue.

A RFID antenna is part of the hardware. If I lower the value of “Finger Threshold” the sensors sometimes are working again

after pressing them very intense and long but then the field of the antenna sometimes activates sensors which are not pressed.

Lowering the values of “Baseline Update Threshold” and “Low Baseline Reset” don’t seem to have any effect.

Best regards

Rainer

Von: SampathS_11 <community-manager@cypress.com>

Gesendet: Donnerstag, 24. September 2020 06:17

An: Rainer Rueckeshaeuser <rueckeshaeuser@autec-gmbh.de>

Betreff: Re: - CY8C20434 used for sensor keypad. Sensor hanging up.

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CY8C20434 used for sensor keypad. Sensor hanging up.

reply from SampathS_11 <https://community.cypress.com/people/SampathS_11?et=watches.email.thread> in PSoC 1 MCU - View the full discussion <https://community.cypress.com/message/251344?et=watches.email.thread#251344>

[RaRu_1223526]

Hello Sampath,

could you already take a look at the project I sent?

At the moment I reset the application periodically in "main.c" with command "M8C_Reset".

After such a reset all sensors work correct again even in case they didn't before because of

pressing the keypad very intense.

Best regards

Rainer

[BragadeeshV]

RaRu_1223526​,

As XiaoweiZ_71​ pointed out, this could be because of the structural deformation caused due to the high pressure on the sensors.

Can you share us the waveform of rawcounts vs baseline when the issue happens? Refer this app note AN2397 - PSoC® 1 and CapSense® Controllers - CapSense Data Monitoring Tools to log this data

https://www.cypress.com/documentation/application-notes/an2397-psoc-1-and-capsense-controllers-capse...

We do not find any attachments in your previous post. Could you please share it again?

Regards,

Bragadeesh

[RaRu_1223526]

Hi,

I have attached a 7z file containing the project.....

Monitoring the signals could be a little difficult

because only pins of SPI interface are led out.

I will look what I can do......

Best regards

Rainer

Von: BragadeeshV_41 <brvi@cypress.com>

Gesendet: Dienstag, 6. Oktober 2020 11:59

An: Rainer Rueckeshaeuser <rueckeshaeuser@autec-gmbh.de>

Betreff: You have been mentioned by BragadeeshV_41 in Re: CY8C20434 used for sensor keypad. Sensor hanging up. in Cypress Developer Community

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You have been mentioned

by BragadeeshV_41 <https://community.cypress.com/people/BragadeeshV_41?et=notification.mention> in Re: CY8C20434 used for sensor keypad. Sensor hanging up. in Cypress Developer Community - View BragadeeshV_41's reference to you <https://community.cypress.com/message/252522?et=notification.mention#252522>

[BragadeeshV]

Hi RaRu_1223526​,

I think there is an issue in the way you are attaching the zip file. I still do not see any attachments in your post. Do the following.

1. Click "use Advanced editor" you see in the top right corner.

2. Click Attach button in the bottom right corner.

3. Select your attachment and upload.

Regards,

Bragadeesh

[RaRu_1223526]

Hi,

I think the zip attachment is filtered out by my mail server…...

[BragadeeshV]

Hi RaRu_1223526​

I have a comment on the main.c file.

CSA_1_UpdateAllBaselines(); should be called after scanning and before checking the staus of the buttons.

while(1) //infinite loop scanning slider

  {

    CSA_ScanAllSensors();    //sample all sensors           

    CSA_UpdateAllBaselines(); 
    CSA_bIsAnySensorActive()
  }
   
Were you able to take a log of the rawcounts and baseline as suggested earlier?

Regards,
Bragadeesh

[Vison_Zhang]

I suspect when you press one or some sensors when high pressure,  the structural deformation caused a large drop in the rawata of other sensors, which pulled the baseline of these sensors down then. When you remove the finger, the rawdata of other sensors quickly restored to its original level but baseline of these sensor cannot follow so fast, finally resulting in false trigger issue.

[RaRu_1223526]

Is there any solution to avoid this?

For me it seems that baseline of the sensors which don’t work any more doesn’t reach original value at all.

Only depowering and powering again lets work all sensors well again.

I will try and wait for longer time. Maybe they will work again after a certain time.

[Vison_Zhang · Accepted solution]

Use material with high mechanical strength as cover material to reduce structural deformation caused by pressure. At the same time, ensure sensors and the cover are tightly pasted with double-sided tape, no gaps should be generated when the cover is deformed.