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PSoC™ 4 Forum Discussions

taas_3144281
Level 5
Level 5
25 sign-ins 50 replies posted 25 replies posted

Hi.

My customer use PSoC 4100S Plus.

I understand that the raw count is adjusted by 85% (+/- 10%) when the IDAC is autocalibrated.

When the resolution is 12 bits, it is recognized as within the range of 3067 (4090 x 0.75) to 3885 (4090 x 0.95).

However, it may fall below or exceed 3067-3885.

I have not touched the sensor.

What could be the cause?

Best Regards.

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1 Solution

Hi taas_3144281​,

Yes, incorrect calibration maybe due to less Cp (< 5pF). If Cp < 5 pF, advise the customer to add a parallel capacitor of 4.7 pF to the sensor pin to intentionally add the sensor capacitance. See figure below:

pastedImage_3.png

Regards,

Bragadeesh

Regards,
Bragadeesh

View solution in original post

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6 Replies
BragadeeshV
Moderator
Moderator
Moderator
First question asked 1000 replies posted 750 replies posted

Hi taas_3144281​,

Can you please check the return of CapSense_Start() and check if the calibration passed or failed?

1. Calibration can fail if the Cp is too high/ too low (Acceptable range is 5 to 200 pF).

2. It could also fail if Fsw is set incorrectly.

Are you using V7.0 CapSense component for testing?

For more info, refer section 5.3.5.7 I am unable to calibrate my system to 85 percent in CapSense design guide

https://www.cypress.com/file/46081/download

Regards,

Bragadeesh

Regards,
Bragadeesh
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Dear Bragadeesh-san

Thank you for your answer.

There seems to be no problem with these two conditions.

If there is no problem, is it stable at 85%?

Best Regards,

Asanuma

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Hi taas_3144281​,

As per validation, we guarantee the following:

pastedImage_0.png

Please let us know the Cp of your sensor and tuning parameters set in your case.

Also, let us know the calibrated rawcounts.

Regards,

Bragadeesh

Regards,
Bragadeesh
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Dear Bragadeesh-san

Thank you for your answer.

I'm sorry. When I asked the customer to check the Cp again, the Cp of the button was 3.

When Fsw was changed from 6000 to 3000, Raw Count was calibrated to 3030.

May I think it's because of Cp?

What is the cause of the change in raw count of ±10% when Cp is within the range?

Best Regards,

Asanuma

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Hi taas_3144281​,

Yes, incorrect calibration maybe due to less Cp (< 5pF). If Cp < 5 pF, advise the customer to add a parallel capacitor of 4.7 pF to the sensor pin to intentionally add the sensor capacitance. See figure below:

pastedImage_3.png

Regards,

Bragadeesh

Regards,
Bragadeesh
0 Likes

Dear Bragadeesh-san

Thank you for your answer.

Best Regards,

Asanuma

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