Touch Electrodes

[SaTau]

Hi,

The "Capacitive Sensing SW User Guide" (AN_K3_CSSWUG) states that the S32K344 can support up to 30 touch electrodes (not going to share this document here since it is proprietary). 

Does this number apply to all S32K3 MCUs? (The obvious exception here being the 48-pin package of S32K311, since 60 pins are required for 30 electrodes- How many electrodes are possible when using this chip?)

[danielmartynek]

Hi @SaTau,

It is different for each part and package.

Please have a look at the TSPC description in the RM and the TSPC Selection list in the S32K344_S32K324_S32K314_IOMUX.xlsx

Regards,

Daniel

[SaTau]

Hi @danielmartynek ,

thank you for your reply.

I have issues comprehending how the number of 30 electrodes for the K344 occurs in the user guide.
I went through the PINMUX-Table and looked which electrodes could theoretically be coupled. I attached an edited table where I added the electrodes I grouped together in order for you to retrace my thoughts.

These are the results:

single-function-pins:
TSPC_GPIO0 + TSPC_ADC0 : 14 electrodes
TSPC_GPIO1 + TSPC_ADC1 : 13 electrodes

"combined" pins:
TSPC_ADC0/TSPC_GPIO0: 7 electrodes (see table: GRP1 A-G)
TSPC_ADC1/TSPC_GPIO1: 4 electrodes (see table: GRP2 A-D)

Makes a total of 38 electrodes which should be possible for the S32K344.
What did I get wrong here?

BR

[danielmartynek · Accepted solution]

I have had a discussion with the owner of the User Guide.

The number 30 is deliberately understated, your calculation seems to be correct.

It is a reasonable number with the consideration that some of the pins might be used for other non-touch-sense functionality.

Regards,

Daniel

[SaTau]

Hi @danielmartynek,

thank you for clarification.

BR