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RE: [AVR-Chat] Made mistake with fuse on Mega88: set to external crystal. Can it be fixed without parallel programming?

2009-12-18 by Tim Mitchell

----Original Message----

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From: AVR-Chat@yahoogroups.com
[mailto:AVR-Chat@yahoogroups.com] On Behalf Of Cat C Sent:
18 December 2009 16:31 To: avr-chat@yahoogroups.com
Subject: RE: [AVR-Chat] Made mistake with fuse on Mega88:
set to external crystal. Can it be fixed without parallel
programming?  

> Thank you Jim.
> That reminds me that I do have all kind of signal
> generators :-) 

Also if you have another AVR board with external crystal on you can run
that up and connect one of the XTAL pins on it to drive your defunct
board. I have rescued a few misprogrammed AVRs that way. You need to use
the output of the oscillator circuit, I can't remember if it's XTAL1 or
XTAL2 but the datasheet tells you.

-- 
Tim Mitchell

Re: Made mistake with fuse on Mega88: set to external crystal. Can it be fixed without parallel programming?

2009-12-18 by Don Kinzer

--- In AVR-Chat@yahoogroups.com, "Tim Mitchell" <tim@...> wrote:
> Also if you have another AVR board with external crystal on you
> can run that up and connect one of the XTAL pins on it to
> drive your defunct board.
I believe that that tactic will work only if the operational AVR board is configured for a full-swing oscillator.  If it isn't, you can always write a quick program to toggle an output pin or generate a signal using a timer.  Also, some AVRs have a "CLKOUT" signal which will make available a full-swing clock signal on an I/O pin.

There are a lot of options for a usable external clock signal.  The venerable 555 timer can be used to generate a clock signal, for example.

Depending on the frequency of the external signal that you use, you may have to re-configure your programmer to run at at a lower frequency.  I think the general rule for ISP programming is that the ISP clock must be no more than 1/4 of the operating frequency of the device being programmed.

Don Kinzer
ZBasic Microcontrollers
http://www.zbasic.net

RE: [AVR-Chat] Made mistake with fuse on Mega88: set to external crystal. Can it be fixed without parallel programming?

2009-12-19 by Cat C

Thanks Tim.

----------------------------------------
> To: AVR-Chat@yahoogroups.com
> From: tim@sabretechnology.co.uk
> Date: Fri, 18 Dec 2009 16:51:15 +0000
...

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> Also if you have another AVR board with external crystal on you can run
> that up and connect one of the XTAL pins on it to drive your defunct
> board. I have rescued a few misprogrammed AVRs that way. You need to use
> the output of the oscillator circuit, I can't remember if it's XTAL1 or
> XTAL2 but the datasheet tells you.
>
> --
> Tim Mitchell

RE: [AVR-Chat] Re: Made mistake with fuse on Mega88: set to external crystal. Can it be fixed without parallel programming?

2009-12-19 by Cat C

Thanks Don.

----------------------------------------
> To: AVR-Chat@yahoogroups.com
> From: dkinzer@easystreet.net
...
always write a quick program to toggle an output pin or generate a signal using a timer. Also, some AVRs have a "CLKOUT" signal which will make available a full-swing clock signal on an I/O pin.

Show quoted textHide quoted text

>
> There are a lot of options for a usable external clock signal. The venerable 555 timer can be used to generate a clock signal, for example.
>
> Depending on the frequency of the external signal that you use, you may have to re-configure your programmer to run at at a lower frequency. I think the general rule for ISP programming is that the ISP clock must be no more than 1/4 of the operating frequency of the device being programmed.
>
> Don Kinzer
> ZBasic Microcontrollers
> http://www.zbasic.net
>