LPC84x capacitive touch not working

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LPC84x capacitive touch not working

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tinman
Contributor I

Are the capacitive touch buttons supposed to work? I have both LPC845 break board and our own board with capacitive buttons and I'm not able to make either to work. None of the SDK examples work with break board, no matter if I try basic examples or analog comparator versions. Only thing I manage to change by touching the capacitive area is the COUNT bits in TOUCH register. No interrupts, always read 0 in  XVAL register. 

I could live with COUNT only if I had just one touch button but unfortunately I have 5 and disabling the pins don't have any effect on COUNT register. Even if I enable only one button by writing XPINSEL in CTRL register touching any of the disabled touch areas change the COUNT.

I wonder why the break board examples won't work either? Has somebody actually tested them with break board? Is there possibly some change in SDK which has broken them?

 

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tinman
Contributor I

One more detail: The only SDK sample program that works does exactly what I suggested above. It lights the green LED on breakout board when COUNT goes below the limit. It does check all the **bleep**: XPINSINDEX, INTSTAT, the works. However when I print out the register values it's the same: absolutely nothing else changes except COUNT but since the breakout board only has one button you can live with it.

Actually the fact that most sample programs don't work according to data sheet and they rely on COUNT only makes me think it's HW problem? Why would the NXP engineers who wrote the SDK samples make this silly workaround otherwise?

 

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_Leo_
NXP TechSupport
NXP TechSupport

Thank you so much for your interest in our products and for using our community.

I noticed that you have another similar case, so I will follow up on this last one that I mention.

Have a nice day!

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