TSS library kinetis K20

[chobin]

Hi everyone,

I'm developing a touch keyboard of 12 buttons using kinetis K20.

I developed the TSS driver using processor expert of code warrior 10.2.

Near the keyboard there is a LCD of 7 inches.

The system doesn't work good. When I turn off and turn on it, sometimes the system doesn't read some buttons. I think that sometimes the calibration is different from start to another one.

I tried to solved the problem changing the sensibility of each button, but the system reads buttons different from the pushed one.

Could someone give me some suggest to stabilize the behavior?

Many thanks in advance for your support.

Best Regards,

Stefano

[Hui_Ma]

Hi,

The LDC display on/off affects the TSI module related electrode capacitance value.

Customer could refer application note AN3863 about touch sensing electrodes hardware design considerations.

From software aspect, if there could eliminate hardware affection, it need to adjust the touch pad detection value according to LCD on/off status.

If possible, It is better to using hardware way to fix the issue.

Wish it helps.

Have a great day,
Ma Hui

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[chobin]

Hi,

thank you for your answer. I saw that there are two methods to measure a capacitance using kinetis: TSI method and GPIO method.

What is the better to use?

Many thanks for your answer.

Best Regards,

Stefano

[Hui_Ma]

Hi Stefano,

TSI and GPIO methods are both using the capacitance value change to check touch panel status.

TSI is using hardware method and GPIO using the software method.

TSI module is more robust and more accuracy.

Wish it helps.

Have a great day,
Ma Hui

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[chobin]

Hi Hui_Ma,

Thank you for your support.

I have two questions about TSI:

1- when I launch my program, it recognizes the touch button correctly, but sometime it stops to recognize some of them. Do you know if there are some TSI registers to know what happened?

2- Sometimes when I launch the same code above, it doesn't recognize some buttons from the beginning. Have you got any idea about it starts without recognize some buttons. Do you think that happened something about the initial auto calibration?

Many thanks.

Best regards,

Stefano

[Hui_Ma]

Hi Stefano,

1> The General Control and Status Register (TSIx_GENCS) includes some TSI status flags to indicate if there with overrun error or out of range or external electrode error occuered;

2> If it is possible, could you provides the TSI module registers value during the code launch? It will help to check which TSI channel met problem.

Wish it helps.

Have a great day,
Ma Hui

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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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[chobin]

Hi Hui Ma,

I have moved from kinetis k20dx256 to k60fx512 because I need more flash. I loaded the same software used for k20 but I have a problem....The k60 microcontroller reads a pushed button of my touch keyboard when  the lcd monted on the board changes the Image.  Please note That I'm using the same hardware used with kinetis k20. If I mount k20 all works correctly. It's very Strange.

I have another problem: when We do the emc tests, the microcontroller (k20 and k60) start to recognize pushed button... nobody pushed them. Have you got any suggestion to protect them from the noise?

Please note That the keyboard is build on a capacitive film develomped following the freescale documents.

Could you help me?

Many thanks in advance for your support.

Best regards,

Stefano