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tahuc_3430236
Level 1
Level 1

Hi,

I am playing with the manual tuning of the Capsense with PSoc 4000s (CY8CKIT-145)

When I play with the compensation IDAC value, I found that the capacitive sensor raw count does not go down to 0. I could not make the raw count less than ~37% of the full scale (For example, the lower bound was 387 count with 10 bit resolution (1023) and the lower bound was 3075 with 13 bit mode (8191).

I really would like to utilize the full scale from 0 to maximum count from the resoultion.

Could anyone explain why I got such lower bound issue and how to solve it?

Thanks.

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1 Solution

There is no limit for raw count. The raw count is converted from scanning on sensor. In other words, if parameters configuration are not suitable, hardware scanning may be not correct which will cause Initialization failed and lead to a saturated raw count value.

However, I still don't know why you'd like to get a 0 value for raw count. Could you let us know which kind of application and product you are developing? we would provide more comments on your questions if we knew it.

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4 Replies
RyanZhao
Moderator
Moderator
Moderator
250 sign-ins First question asked 750 replies posted

Refer to AN85951.

RawCount.PNG

Rawcount is not only decided by parameters shown in the component configuration GUI, but also related with some system parameters, such Cs, Vref.

Thanks,

Ryan

RyanZhao
Moderator
Moderator
Moderator
250 sign-ins First question asked 750 replies posted

BTW. May I know the reason, why would you like to tune the rawcount from 0 to full scale?  The rawcount should stay at a stable level with no touch.

Thanks,

Ryan

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tahuc_3430236
Level 1
Level 1

Thanks for your reply,

In your captured text, it says if

     I_COMP > Vref * Cs* Fsw

then the raw count will be zero.

However, when I keep increasing I_COMP, the raw count is not zero but it is saturated with a certain value. Usually, the saturated values from different Modulator & Sensor clock frequency were around powers of 2 (i.e. 512, 1024, 2048...).

So I suspect that the initialization API would set some lower limit of the raw sensor count. But I could not find it yet.

Does anyone have an idea where such lower bound or saturated minimum raw count from?

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There is no limit for raw count. The raw count is converted from scanning on sensor. In other words, if parameters configuration are not suitable, hardware scanning may be not correct which will cause Initialization failed and lead to a saturated raw count value.

However, I still don't know why you'd like to get a 0 value for raw count. Could you let us know which kind of application and product you are developing? we would provide more comments on your questions if we knew it.

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