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Alexrs

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Joined: 20 Feb 2012
Posts: 4

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PostPosted: Mon Feb 20, 2012 12:35 am    Post subject: Fuse bits Reply with quote

Hello.
I am Very new to Bascom. But thatís not an excuse to ask silly questions.
I am using Atmega 8 16pu chip.
Using the Avr studio v5.0 1223 to upload and set fuses.
Not having to much trouble with the programming at this time..
I can upload with no issues at all.

What I have issues with is Avr studio and the fuse settings.. I have BRICKED two chips trying to get it right.
I have done a lot of reading up on Avrstudio but there is nothing that helps me.
The High Fuse I am setting to D9 and the Low Fuse to E8.
The SUT_CKSEL setting i HAVE selected is EXTRCOSC_8MHZ_12MHZ_18CK_64MS.
Is there anyone can please advise on were I am screwing up.

Regards Alex
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kimmi

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Joined: 24 Feb 2006
Posts: 1922
Location: Denmark

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PostPosted: Mon Feb 20, 2012 12:43 am    Post subject: Reply with quote

Hi
do you have a crystal 8Mhz to 12Mhz connectet to M8 ? LOW = E8
You set fuse to use EXTERN crystal

Engbedded Atmel AVRģ Fuse Calculator

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JC

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Joined: 15 Dec 2007
Posts: 490
Location: Cleveland, OH

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PostPosted: Mon Feb 20, 2012 2:09 am    Post subject: Reply with quote

In addition to Kimmi's comments above, there is an entire Tutorial on Un-Bricking an AVR on the AVR Freak's web site:

http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=106325

JC
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kimmi

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Joined: 24 Feb 2006
Posts: 1922
Location: Denmark

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PostPosted: Mon Feb 20, 2012 3:31 am    Post subject: Reply with quote

If you donít have a Jtag, or STK500

You can use a external clock if you messed the fuses settings.
Connect a external clock (around 1Mhz) on the clock pin (XTAL1 PIN)
and reprogram fuse again

else read this

Quote:
External RC oscillator setup

The frequency in this mode is calculated by formula f=1/(3RC) while C should be at least 22pF. If CKOPT is programmed (unchecked),
then Internal capacitor 36pF between XTAL1 and GND is enabled,
then there is only resistor needed.

Ft[MHz]=1000/(3∑R1[kΩ]∑C1[pF])




R1 = 1K
C = use internal Co 36pf CKOPT was unchecked

1000 / (3 * 1 * 36) = 9.25925926 Mhz

So you can add a 1K RES between +5V and XTAL1

+5V --- RES----XTAL1 PIN

Well its a try maybe it works I never tested this option on real hardware

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Alexrs

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Joined: 20 Feb 2012
Posts: 4

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PostPosted: Mon Feb 20, 2012 8:08 am    Post subject: Reply with quote

Hi and thanks for replays.
Kimmi I have a 16 MHz With caps connected.
Thanks for the info on unbricking the chips.
Will check the crystal connections later on.
I have 1 more chip to play with then I will do something with the chips.

Regards Alex
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kimmi

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Joined: 24 Feb 2006
Posts: 1922
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PostPosted: Mon Feb 20, 2012 8:57 am    Post subject: Reply with quote

Hi,
If you have External crystal 16 mhz the fuse is WRONG

ATMEGA8 (not the L version its only 8Mhz)
the fuse must be :
HIGH = D9
LOW = 7F or FF if BODLEVEL unchecked

use Ext. Crystal/Resonator High Freq.; Start-up time: 16K CK + 64 ms the last one

not Ext. RC Osc. 8.0 MHz - 12.0 MHz; Start-up time: 18 CK + 64 ms
its for RC osc not crystal
RES and CAP as in my last post

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Alexrs

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Joined: 20 Feb 2012
Posts: 4

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PostPosted: Mon Feb 20, 2012 11:49 am    Post subject: Reply with quote

Thank YOU.
Thats my error.
Sorry for posting in wrong Area.
Regards Alex
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ajvuik

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Joined: 28 Apr 2011
Posts: 46
Location: Netherlands

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PostPosted: Mon Feb 20, 2012 7:31 pm    Post subject: Reply with quote

Well, I was about to offer to send the uC's to me and I'll debrick them for ya with my STK500, but I guess it'll be cheaper to just buy 2 new ones I guess Very Happy

*edit*

Or you could try:
http://www.societyofrobots.com/member_tutorials/node/239

or, if you are afraid you'll lock more chips, you can build:
http://www.scienceprog.com/avr-serial-and-parallel-high-voltage-programmer/
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