AVR-Chat

Hi again
By the way Application notes AVR242 on page 4 has a interesting four digit 7 segment LED, 4*4 keyboard
with a AT90S1200 but it uses two ports B & D.   not that I would use it, it is just food for thought.


From Eric





----- Original Message -----
From: "Eric" <erichards@clear.net.nz>
To: <AVR-Chat@yahoogroups.com>
Sent: Saturday, February 19, 2005 9:41 AM
Subject: Re: Amazon Re: [AVR-Chat] The keyboard



I'm confused Stefan
why switch the rows from output to input & Columns from input to output? it just sounds like a waste of
software space for what it is worth.


From Eric





----- Original Message -----
From: "Stefan Trethan" <stefan_trethan@gmx.at>
To: <AVR-Chat@yahoogroups.com>
Sent: Saturday, February 19, 2005 9:28 AM
Subject: Re: Amazon Re: [AVR-Chat] The keyboard



On Fri, 18 Feb 2005 15:16:04 -0500, Dave VanHorn <dvanhorn@dvanhorn.org>
wrote:

>
> The easy way to do a matrix keyboard, is to take rows (or columns) and
> make
> them inputs pulled up, and take the other side (col or row) and make them
> the scanned outputs, active low.
> So, when you are seeing all highs, no keys are pressed.
> When you see a low on any row, then you check what col you have set low,
> and now you know what key(s) are pressed.
>


I am currently making something with a 3x4 keyboard.
I have connected the 3 columns to the 3 external iterrupts, and the 4 rows
to I/O.
The plan is to set the column pins (interrupts) to pullup, and input, and
the rows to output, low.
My hope is when someone presses a key the interrupt line goes low, causing
a interrupt and in the ISR i switch the rows input and columns output to
see which button it was.

Would be nice to know if this will actually work, i just guessed...

ST



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