AVR-Chat

On Fri, 18 Feb 2005 15:34:36 -0500, Dave VanHorn <dvanhorn@dvanhorn.org>  
wrote:

>
>>
>> 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...

> Sounds right to me, just set a timer to change the row outputs
> periodically, say every 100mS or so.


Thanks,

but why should i change the row outputs?
I thought i let them all low, until there's a interrupt, and in the ISR i  
change the rows from out to in and make the colums low. The row input that  
goes low would show the pressed key?

ST