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RE: [avr-gcc-list] Newbie question

From: Stu Bell
Subject: RE: [avr-gcc-list] Newbie question
Date: Wed, 25 Feb 2009 16:37:23 -0700

> > If A/D-Converter and AnaComp are unused, you can 
> > use the ADC's input MUX and connect it's output 
> > with an AC input. The AC can then be used as input 
> > for InCapt of T1. So you can measure up to 7 lines
> > in time slice mode (ICP, ADC0-ADC5).
> Really?   
> Interesting.. That would largely solve my problem if true.

Hard-core analog designers have told me that digital is just very poorly
designed analog. :-)

You still have a latency problem since you need to grab the ICP buffer
before the next edge.  At 5 uS on a 4 MHz processor, that's a time
buffer of 20 CPU cycles - NOT MUCH!  A well-crafted ISR can do it, but
it's tight.

Another option would be to upgrade to an ATmega64 (or ATMega128).  That
has 2 16-bit counters with ICP.  You can slave the counters together so
that you end up with synchronized counts from the two edges.  Then
there's not a latency issue (or nearly as bad a one).

I checked, and unfortunately the mega324(P) series has the same timer
configuration as your mega32.

Best regards, 

Stu Bell 
DataPlay (DPHI, Inc.) 


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