AVR-Chat

Hello Sir, 
I am getting some hardware problem. I have made one serial communication code using codevision and STK500 kit for atmega32. When I am running this code on STK500 it works proper, but when I am running this code on circuit made by me, I am getting garbage values on Hyper Terminal. So can you suggest me how can i solve it? 

For reset pin I have connected 10k resistor and 10uF capacitor. Capacitor I am connectiong to ground at one end. and giving 5v supply . so my circuit is as follow/.
                                                
                    10k                           
o------------^^^^^^^^^^^---------------------|RST
                                      |
                                      |
                                      |
                                    === 10uF
                                      |
                                      |
                                  ---------     
 
R.P.Modi


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On Apr 12, 2008, at 2:30 PM, rakesh modi wrote:

> Hello Sir,
> I am getting some hardware problem. I have made one serial  
> communication code using codevision and STK500 kit for atmega32.  
> When I am running this code on STK500 it works proper, but when I am  
> running this code on circuit made by me, I am getting garbage values  
> on Hyper Terminal. So can you suggest me how can i solve it?
>
> For reset pin I have connected 10k resistor and 10uF capacitor.  
> Capacitor I am connectiong to ground at one end. and giving 5v  
> supply . so my circuit is as follow/.
>
>                    10k
> o------------^^^^^^^^^^^---------------------|RST
>                                      |
>                                      |
>                                      |
>                                    === 10uF
>                                      |
>                                      |
>                                  ---------

Remove the capacitor.

--
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

>  > For reset pin I have connected 10k resistor and 10uF capacitor.
>  > Capacitor I am connectiong to ground at one end. and giving 5v
>  > supply . so my circuit is as follow/.
>  >
>  >                    10k
>  > o------------^^^^^^^^^^^---------------------|RST
>  >                                      |
>  >                                      |
>  >                                      |
>  >                                    === 10uF
>  >                                      |
>  >                                      |
>  >                                  ---------
>
>  Remove the capacitor.


I wouldn't go quite that far, but I would change it to 0.1uF.

There are other possible problems, which we have  discussed on here previously..

Check that your oscillator is actually running at the speed that you
think that it is.

Check that the connection between the PC and the AVR is correct,
including the ground lead!

Check that the AVR is set up for the same word format and bit rate
that the PC is.

Check that the USART is initted properly.

Check that your code waits for the transmit buffer to empty before
sending the next char...


Many things to verify, and until you get SOME sort of output working
right, it will be difficult to sort things out.  Hopefully you have a
scope, or some means to verify basic operation.

Don't accept "sort of working" as "right".  I got bit once with a VERY
nasty problem that showed up first as several different slightly wrong
things. (search the group for references to the CKOPT FUSE for
details)  Serial comms being slightly at the wrong baud rate was one
of the symptoms.

On Apr 12, 2008, at 6:24 PM, David VanHorn wrote:
>>
>> Remove the capacitor.
>
> I wouldn't go quite that far, but I would change it to 0.1uF.

Agreed that 0.1 is better than 10 because there can be a good bit of  
leakage in a 10uF electrolytic so that it might not charge with a 10K  
series resistor.

But the ATmega family works pretty good out of reset running with the  
longer oscillator startup delays plus reasonable BOD settings, with  
nothing on the RESET pin at all. I generally put a 47k pullup on the  
RESET pin.

--
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

> Agreed that 0.1 is better than 10 because there can be a good bit of
> leakage in a 10uF electrolytic so that it might not charge with a 10K
> series resistor.

Rise time is also an issue, check the spec sheet.