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One Input -> 112 touch sensor !!! ( PCF8574 )
Posted: 22 Sep 2012, 17:07
by floppi
simply like a keyboard , go there to read the explanation :
in french :
http://alpmn.franceserv.fr/matrices.htm
Google translation in english :
http://translate.google.fr/translate?sl ... trices.htm
Re: One Input -> 112 touch sensor !!! ( PCF8574 )
Posted: 22 Sep 2012, 17:41
by mattallen37
The main problem with a matrix, is key ghosting. It works perfectly if you only press one key at a time, but otherwise it can ghost really badly.
The same concept can be applied to run many LEDs from few IOs. Actually, with LEDs, you can charlieplex them instead.
Re: One Input -> 112 touch sensor !!! ( PCF8574 )
Posted: 22 Sep 2012, 19:44
by floppi
mattallen37 wrote:The main problem with a matrix, is key ghosting. It works perfectly if you only press one key at a time, but otherwise it can ghost really badly.
The same concept can be applied to run many LEDs from few IOs. Actually, with LEDs, you can charlieplex them instead.
If you read all this link, there is a solution for this, a way to manage several keys pressed at the same time.
look at : Forged keyboard type "polyphonic" - Addition of diodes
I am currrently trying to build a 20 keys numeric keyboard in this way.
Re: One Input -> 112 touch sensor !!! ( PCF8574 )
Posted: 23 Sep 2012, 22:47
by floppi
Unlike that was said on this site, I've got key ghosting !
My 20 touch keyboard works well but some key combination causes bad key readings !
About Charlieplex, 3 state output/input are needed to work.