PSoC5LP Finger threshold and noise level for CapSense tuning

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Hi,

We are currently doing CapSense tuning for PSoC 5 LP.

The following phenomenon occurred while tuning.

Tuning.png

The above screen is in the initial state.
A high noise level is displayed.

Just changing the finger threshold(FT) from 190 to 180 lowers the noise level as shown in the screen below.

We can't understand that the noise level changes just by changing the finger threshold(FT).

This phenomenon happens occasionally but do you understand why?
Or is there any way to deal with it?

Regards,

0 Likes
1 Solution

Hello Masashi-san,

I checked with your project in the kit. I see that you have set the Widget resolution parameter (Advanced tab-> Sensors configuration) to 8-bit. Could you pls change this to 16-bit and check if you still face this baseline update issue?

At my end, the baseline tracks the raw counts as expected.

In general, when the signal is greater than 255, you need to use 16-bit resolution and 8-bit resolution when signal is lesser than or equal to 255.

I hope this resolves your query.

Thanks & Regards,

Shanmathi

View solution in original post

0 Likes
10 Replies
ShanmathiN_06
Employee
Employee
100 replies posted 50 replies posted 25 replies posted

Hi,

This issue seems strange. Ideally, changing the finger threshold should not cause any change in raw counts.

Could you pls check the following and post the updates?

Can you read the raw count value using Bridge control panel or print the raw count value in UART? This test is to ensure that Tuner I2C host is reading the correct raw counts value.

Also, is there any scenario when this phenomenon is observed? Maybe, I can try at my end with the same configuration (Pls send yours) and see if I could reproduce the issue.

I see from the images that SNR is lesser even though noise level is low. Could you pls confirm this? Is the signal also lesser when noise is lesser?

Thanks,
Shanmathi

0 Likes

Hi,

Were you able to resolve your issue? Pls post your updates.

Thanks,

Shanmathi

0 Likes
MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Shanmathi-san,

Sorry for the late reply.


We have debugged the board.

Raw count was output correctly.

The cause of the problem is:

1. Power on the board of PSoC5LP.

2. Turn on LED for CapSense.

The LED lighting at this time appears as noise.

3. Changing the finger threshold updates the baseline and reduces the noise level.

Therefore, I thought that setting the noise threshold high would solve the problem, but a new problem occurred.

A phenomenon occurs in which the baseline does not follow even below the noise threshold.

Do you know why the baseline does not track noise?

Regards,

Masashi

0 Likes

Hello Masashi-san,

Have you enabled "sensor auto reset" option (CapSense CSD component configurator window -> Advanced tab)?

If you have enabled auto reset option, then baseline is always updated independent of the noise threshold. If not, then baseline will be updated whenever difference counts/ signal is lesser than noise threshold.

Pls send your raw count wave forms, when you face the baseline update issue, along with your CapSense configuration.

Thanks,
Shanmathi

0 Likes
lock attach
Attachments are accessible only for community members.
MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Shanmathi-san,

Each channel was found to follow or not follow the baseline.

It was also found that all channels follow the baseline when set to auto.

Does the baseline fail to track due to parameter settings?

For example, IDAC value is low, Analog Switch Divider value is low, etc.

We will send you a CapSense configuration file for reference.

However, the operation may differ depending on the surrounding environment,

so your company may not be able to reproduce it.

Regards,

Masashi

0 Likes
lock attach
Attachments are accessible only for community members.
MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Shanmathi-san,

We created a project to reproduce with CY8CKIT-050.

I will attach the project.

It can be reproduced by the operation of button 6 of capsense component (P5[6] on the Kit).

gephing.png

Even if you touch the Caps button gradually, Baseline does not follow.

tuning.png

You can also check that it is below the noise threshold with a bar graph.

Regards,

Masashi

0 Likes
MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Supplement.

Immediately after writing the project to DVK, the baseline may follow correctly.
At that time, please change the noise threshold value.
For example, noise threshold from 80 to 75 or 85.
You probably can reproduce the problem behavior.

0 Likes

Hello Masashi-san,

I checked with your project in the kit. I see that you have set the Widget resolution parameter (Advanced tab-> Sensors configuration) to 8-bit. Could you pls change this to 16-bit and check if you still face this baseline update issue?

At my end, the baseline tracks the raw counts as expected.

In general, when the signal is greater than 255, you need to use 16-bit resolution and 8-bit resolution when signal is lesser than or equal to 255.

I hope this resolves your query.

Thanks & Regards,

Shanmathi

0 Likes
MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Shanmathi-san,

Certainly when changing to 16 bit,
The baseline followed the RAW data even if the noise threshold was changed.

Do you think this is a bug in PSoC Creator?
We take care when tuning.

Thanks,

0 Likes

Hello Masashi-san,

The Tuner interface expects the user to choose widget resolution according to the signal (difference between raw counts and baseline).

So, this would be treated as a user error. However, I agree that Tuner interface should throw a warning if the signal and widget resolution does not match.

In general, these bugs were resolved in PSoC 4/6 CapSense component (https://www.cypress.com/documentation/component-datasheets/psoc-4-capacitive-sensing-capsense )

So, you could use those devices for better CapSense functionality, if all your other application requirements are supported too.

Thanks,
Shanmathi

0 Likes