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MPR121 retriggering when holding on a pad / can't recover from "touched" state

Question asked by zilaihong on Sep 16, 2014
Latest reply on Nov 13, 2014 by Bryce Osoinach

My MPR121 would keep the "touched" and "released" states when a finger is holding on a pad. And one of the electrodes even can't recover from the "touched" state sometimes.

Btw, when I have 2 fingers holding 2 electrodes, the glitch won't happen.

 

I used all settting in the application note AN3944.

 

One thing I noticed that in application note AN3747, it recommended to use thin <0.2mm traces for electrodes connections. But on my PCB I used 0.8mm traces which seems too wide. And I used 100% ground plane around the traces and the electrodes, 0.4mm gap between the traces / electrodes and the ground plane. Will this be the main cause of the problem?

 

Btw, I have another question, does MPR121 reset all its internal settings when rebooted? In other words, even if I really messed up the settings on the registers, when I upload a new correct one and reboot, it would recover from a "clean" state and start up with the new setting?

 

Thanks!

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