Slider on STM8 - need help

[brunomontanari9]

Posted on January 20, 2010 at 09:39

Slider on STM8 - need help

[brunomontanari9]

Posted on January 19, 2010 at 09:45

Hello,

I'm using the STM8S105K6, with the cap touch library v2.2. I've made a board according to the documentation and the layout is OK (already sent it to ST support). If needed, I can post a image of the layout. All the single keys works fine :D , my problem is the instability on the slider position. I'm considering the struct ''sMCKeyInfo[0].Position'' to get the slider position (it has 5 channels). When I'm moving my finger across the slider, I can see that the values the struct give me are not linear(it is supposed to be linear, I guess) and that when I'm close to any of the extremities - channel 1 or 5, on most of the cases, the position shows some calc error, as if I were on channel 3 or so, but if I move just a little closer to the extremity it reaches the correct values, but there is this huge error before reaching the correct position. How can I correct this? apparently there is something that is not taken into account on the position equation... This could also be just bad calibration? I've tried many different calibrations to resolve this, none worked so far. Thanks in advance for your help. :-]

[maxime2399]

Posted on January 19, 2010 at 15:10

Make sure you selected the correct MCK type in the configuration file.

Sliders need a dead end on each side while wheels do not. Try to follow the method in the attached pdf to characterize your slider and use the library balancing feature. If not sufficient, increase your slider detection threshold to avoid to detect the 'noise'. I hope it helps...

[brunomontanari9]

Posted on January 20, 2010 at 09:39

hi,

thank you for the pdf, I've made a similar study before, attached is what I've found. With the individual calibration I guess I'll be able to make them all have the same amplitude. This should help on the resolution What did you mean by dead end? The position shows a value from 0 to 255...they are my dead ends, right? Thanks!

[Max]

Posted on February 03, 2010 at 13:52

The dead end is a an area at the beginning of the slider that always reports 0 and one at the end of the slider that always report 255.

This is usually one half of the electrode on each side. This is mandatory because in these areas, the finger only touch one electrode, therefore a precise positioning on those ends is not possible