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Question about PORTA and PORTC

Question about PORTA and PORTC

2005-01-15 by dv7839

I'm very new to this, so I may not have things setup right but ...

I have a STK500 with a AT90S8515.  I would like to use PORTA for 
digital I/O.  I setup DDRA to 0xff (all output) and wrote 0xf0 to 
PORTA.  I got out my logic probe, and expected for half of the pins 
to be high, and the other half to be low.  What I found was that 
they behaved as if they were not connected.  I tested some known 
values, and so I know the logic probe is working.  I moved the whole 
thing to PORTC, and had the exact same problem.  Any suggestions???  
PORTB is already in use, and works.  I tried removing that portion 
of the circuit/program to isolate the problem, but it didn't help.  
It appears to be only with PORTA and PORTC.  I'm guessing there is 
something else to setup in order to "enable" PORT A/C, but I just 
can't figure it out.  Any help would be GREATLY appreciated.

Thanks,
dan

RE: [AVR-Chat] Question about PORTA and PORTC

2005-01-15 by Lasse Madsen

Sounds as if you have wrecked the port..
 
Or . Have you connected the AVCC pin to the SAME voltage net as VCC ?
 
Regards
Lasse Madsen
 
  _____  
Show quoted textHide quoted text
From: dv7839 [mailto:danvernon@earthlink.net] 
Sent: 15. januar 2005 18:43
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Question about PORTA and PORTC
 

I'm very new to this, so I may not have things setup right but ...

I have a STK500 with a AT90S8515.  I would like to use PORTA for 
digital I/O.  I setup DDRA to 0xff (all output) and wrote 0xf0 to 
PORTA.  I got out my logic probe, and expected for half of the pins 
to be high, and the other half to be low.  What I found was that 
they behaved as if they were not connected.  I tested some known 
values, and so I know the logic probe is working.  I moved the whole 
thing to PORTC, and had the exact same problem.  Any suggestions???  
PORTB is already in use, and works.  I tried removing that portion 
of the circuit/program to isolate the problem, but it didn't help.  
It appears to be only with PORTA and PORTC.  I'm guessing there is 
something else to setup in order to "enable" PORT A/C, but I just 
can't figure it out.  Any help would be GREATLY appreciated.

Thanks,
dan





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Re: Question about PORTA and PORTC

2005-01-15 by dv7839

Oh boy ... I feel dumb :(  I've spent hours on this, and as it turns 
out, I was writing the wrong program to the chip.  Well, I'm a 
little bummed about the time I wasted, but then again at least the 
chip is ok.

thanks
dan
--- In AVR-Chat@yahoogroups.com, "Lasse Madsen" <lasse.madsen@e...> 
wrote:
> Sounds as if you have wrecked the port..
>  
> Or . Have you connected the AVCC pin to the SAME voltage net as 
VCC ?
>  
> Regards
> Lasse Madsen
>  
>   _____  
> 
> From: dv7839 [mailto:danvernon@e...] 
> Sent: 15. januar 2005 18:43
> To: AVR-Chat@yahoogroups.com
> Subject: [AVR-Chat] Question about PORTA and PORTC
>  
> 
> I'm very new to this, so I may not have things setup right but ...
> 
> I have a STK500 with a AT90S8515.  I would like to use PORTA for 
> digital I/O.  I setup DDRA to 0xff (all output) and wrote 0xf0 to 
> PORTA.  I got out my logic probe, and expected for half of the 
pins 
> to be high, and the other half to be low.  What I found was that 
> they behaved as if they were not connected.  I tested some known 
> values, and so I know the logic probe is working.  I moved the 
whole 
> thing to PORTC, and had the exact same problem.  Any 
suggestions???  
> PORTB is already in use, and works.  I tried removing that portion 
> of the circuit/program to isolate the problem, but it didn't 
help.  
> It appears to be only with PORTA and PORTC.  I'm guessing there is 
> something else to setup in order to "enable" PORT A/C, but I just 
> can't figure it out.  Any help would be GREATLY appreciated.
> 
> Thanks,
> dan
> 
> 
> 
> 
> 
>   _____  
> 
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