Dragon and external clocks

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nick-123
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Posted by nick-123: Fri. Jul 11, 2008 - 02:06 AM
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Hi,

Perhaps I'm stupid but I used a dragon to program some chips. Normally I hook the dragon up using the isp interface to a daughterboard to program the chip. (daugherboard with power). So far no problems yet but today...

Today I hooked a chip directly to the onboard zifsocket.

I tried to set the clock to external 8MHz->..
And suddenly the dragon did complain that it can't find the chip.
Apparantly it only works if the fuse is set to an internal clock. I did check this with diffeerent avr's.

It this the normal behaviour of the dragon?
I could not find an answer to this problem in the extensive dragon posts. I hope someone could enlighten me.

Thanks,

Nick

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AVR Microcontrollers, megaAVR and tinyAVR
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js
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Posted by js: Fri. Jul 11, 2008 - 02:54 AM
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Quote:
I tried to set the clock to external 8MHz->..
And suddenly the dragon did complain that it can't find the chip.
That would be like cutting the hose to the carburettor and expecting the car to run. :)

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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nick-123
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Posted by nick-123: Fri. Jul 11, 2008 - 03:09 AM
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John,

??????

Question: Is this normal behavior?

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Kartman
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Posted by Kartman: Fri. Jul 11, 2008 - 03:39 AM
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In short, yes. You've selected an external oscillator so you've got to provide one. If you don't provide one, then it won't program. Unfortunately, selecting the wrong fuse option is 'sudden death'. You need to provide an external clock source to recover.

Also - an external clock is not an external crystal - two different options at work here.

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nick-123
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Posted by nick-123: Fri. Jul 11, 2008 - 03:43 AM
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Thanks Kartman,

There should be a warning somewhere is the manual....
I thought about the oscillator, but could not find any on the pcb, but some components are too small for my eyes, so I thought perhaps it contained one.

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js
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Posted by js: Fri. Jul 11, 2008 - 03:43 AM
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Quote:
Is this normal behavior?
Yes, you switched off the clock from the chip. So unless you have a clock input on XTAL1 (as you selected external clock) the chip is dead. :(

So basically the chip can run off:
1) Internal 8MHz or 1MHz clock. (default)
2) External clock. (you supply the clock as above. NOT just a crystal but an oscillator)
3) External crystal and caps.

The Dragon does not have any way of supplying 2 and 3.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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nick-123
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Posted by nick-123: Fri. Jul 11, 2008 - 03:48 AM
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John,

Lol,

So I could do the following:
program hex file
program lock fuses and then as the last step the other fuses.

But then it can't be verified anymore.

What a bummer the dragon does not contain a clock source....

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js
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Posted by js: Fri. Jul 11, 2008 - 04:00 AM
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Well, if you have a board with all the bits mounted then it is no longer a problem. :)

The Dragon is not designed for complicated projects but simple ones using the internal clock I would assume.

I never use the Dragon for programming anyway but debugging only, so cannot comment much.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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nick-123
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Posted by nick-123: Fri. Jul 11, 2008 - 04:07 AM
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Yeah, that's what I use it for most of the time. But then I thought of a quick programming job.

It turned out to cost me more time then I thought it would. :oops:

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