No response from meg640

nisse · Joined: 14 Dec 2006 Posts: 50

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?

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

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.

nisse · Joined: 14 Dec 2006 Posts: 50

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

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

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

nisse · Joined: 14 Dec 2006 Posts: 50

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

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Hello nisse

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

Regards Paul