MSP430FR2633: Advice on designing small metal switches

Is it using mutual or self-capacitance mode?

Evan

Hi, Evan

it is using self-capacitance mode.

The switch size is 1 to 1.3 cm, and the switch interval is about 0.5 to 1 cm.

Thanks,

Astro

Hi Astro,

Mutual capacitance is better for designs where the electrodes will be close together.

Regards,

Evan

Evan

Is there any way to deal with the self-capacity method?

Thanks,

Astro

Hi Astro,

Per the CapTIvate design guide it is not recommended:

You can read more about it here: https://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/CapTIvate_Design_Center/1_83_00_08/exports/docs/users_guide/html/CapTIvate_Technology_Guide_html/markdown/ch_basics.html#tightly-coupled-e-fields

If you choose self-cap mode the design may have issues with cross coupling and false triggering.

Regards,

Evan

Hi, Evan

>If you choose self-cap mode the design may have issues with cross coupling and false triggering.

Does Metal Touch support mutual capacity method?

Thanks,

Astro

Are you refering to this type of meta touch:

Regards,

Evan

Hi, Evan

In summary, is it correct to understand that it is difficult to suppress malfunctions when designing with metal touch under the following conditions?
■ The switch size is 1 to 1.3 cm, and the switch interval is about 0.5 to 1 cm.

Thanks,

Astro

Evan

It's a little urgent, so it would be very helpful if you could get an answer as soon as possible.

Hi Astro,

Do you have any ground plane around the buttons and/or on the backside of the PCB? Without any or little ground around the sensors, the e-fields will tend to cross couple with neighboring buttons. Can you share PCB file (pdf or gerber) for us to quickly review?

Although I suspect this may be a sensitivity and touch threshold issue. What is your conversion count setting and did you set the touch thresholds appropriately?  You can start with a conversion count around 250.  Set conversion gain = 100 and don't change it.  See if you still have same issue.

You can also post your CAPT_UserConfig.c and .h files and I can tell what you have setup and can provide suggestions.

Hi, Dennis

Thank you for your advice.

We will contact you shortly regarding the confirmation items you have provided.

Is it possible to utilize private messages for layout sharing?

Thanks,

Astro