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No response from meg640

 
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nisse

Bascom Member



Joined: 14 Dec 2006
Posts: 50

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PostPosted: Wed Apr 09, 2014 9:53 pm    Post subject: No response from meg640 Reply with quote

Hi
I have a meg640 that has been working fine untill just now.
I was programming it from Bascom with a USB-ISP programmer when downloading suddenly slowed down. It finished, but in more than double the normal time.
After this the chip doesn't work, I don't even get any response when trying to reprogram it, no chip ID, nothing but unknown chip FFFFF.
The programmer works, tried it with other chips. The meg640 is run from an external clock.
I suspect a fuse bit or two got messed up... Sad
Any ideas on how i can solve this?
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albertsm

Administrator



Joined: 09 Apr 2004
Posts: 5095
Location: Holland

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PostPosted: Thu Apr 10, 2014 10:03 pm    Post subject: Reply with quote

it is simple to solve : connect a clock signal (for example oscillator output from a working avr circuit) to the xtal input. Look in the pdf to see which pins server as input and output.
then change the fuse bytes to the proper value.

some times pulling the usb cable and plug it again can help too. when you use the jumper to power the circuit you need to take care not to draw too much current from the usb port.

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Mark
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nisse

Bascom Member



Joined: 14 Dec 2006
Posts: 50

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PostPosted: Fri Apr 11, 2014 6:32 am    Post subject: Reply with quote

Thanks Mark, but its already running from an external oscillator Sad
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albertsm

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Joined: 09 Apr 2004
Posts: 5095
Location: Holland

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PostPosted: Fri Apr 11, 2014 8:58 am    Post subject: Reply with quote

but is that external osc still working ?
and does the programmer still work ?

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nisse

Bascom Member



Joined: 14 Dec 2006
Posts: 50

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PostPosted: Fri Apr 11, 2014 10:26 am    Post subject: Reply with quote

yes
yes
Guess I have to get the 0.4mm solder iron out and replace that AVR Sad
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Paulvk

Bascom Member



Joined: 28 Jul 2006
Posts: 1198
Location: SYDNEY

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PostPosted: Sun Apr 13, 2014 11:42 pm    Post subject: Reply with quote

Hello nisse

Have you tried a 1Mhz clock to the AVR others have noted that this has worked

Regards Paul
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