Reading a messed up keyboard

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Hi,

So, I messed up a little "keyboard" design. I wanted to scan four BCD switches using one PORTD. While designing it, I didn't remember that I should use the matrix for multiple connections (the one with diodes). Now, I have a matrix with the possibility of multipple connections at once, but without the diodes.

Is there any way to scan it anyway?

Or will I have to add 16 diodes?
Thanks,

David

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There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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I don´t see a way without the diodes (or resistors)

Maybe you find BCD switches with built in diodes.

Klaus
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Look at: www.megausb.de (German)
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2 BCD switches connected to R/2R ladder and output to ADC...

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Oh well, I'll go with the diodes. But note that it will be the most ghastliest board hack you've ever seen.

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Just to be on the safe side: This is the correct schematic?
(I almost certain so, but just to avoid further soldering, could someone check it?)

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There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Yes. If you make one of the upper 4 lines low, the code of that switch is on the 4 lower lines. And with a 5V AVR you're safe (level-wise), and with 3.3 quite safe ;)

Nard

PS the General Electronics Forum is IMO a better place for these kind of questions.

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