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TSS keypad with very low delta values

Question asked by Francesco Prosperi on Jan 17, 2013
Latest reply on Jan 25, 2013 by Francesco Prosperi

Hi all,

 

I'm trying to improve the delta values for my custom board featuring S08PT32 (with 6 electrodes). Currently delta values are around 5.

 

Although a bit outdated, following the TSI tuning online application note (on the Freescale Technical Information Center),

it seems that the variables to be changed are:

 

#define TSS_TSI_PS_LOW_LIMIT        0  /* Low Limit of External OSC Prescaler register value for TSI auto-calibration */

#define TSS_TSI_PS_HIGH_LIMIT        7  /* High Limit of External OSC Prescaler regiters value for TSI auto-calibration *

 

I tried changing such values together with

#define TSS_TSI_EXTCHRG_LOW_LIMIT  0  /* Low Limit of External OSC Charge Current register value for TSI auto-calibration */

#define TSS_TSI_EXTCHRG_HIGH_LIMIT  7  /* High Limit of External OSC Charge Current register value for TSI auto-calibration */

 

and the TSS_TSI_RESOLUTION (currently 11).

 

but with no effect.

 

To improve delta, I could use signal multiplying but I don't see it as a good way to go.

 

Is there any way I am missing to improve delta values to be around 20-70 (as suggested in the application note previously pointed out) ?

 

Best regards,

 

Francesco Prosperi

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