newbie - changed CKSEL and now programmer won't connect

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dougm
 
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Joined: Thu Feb 26, 2009 2:47 pm

newbie - changed CKSEL and now programmer won't connect

Post by dougm »

Hi, just started moving from PIC to AVR and am trying to create a low power app, so I wanted to change the clock speed to 32Khz. First thing I did was program the chip to blink an LED at 100ms intervals (using the default 1Mhz clock speed).

Then I went into AVRDude and changed the LFUSE from 0x62 (the original 1Mhz clock speed) to 0x64 (the new 32Khz clock speed) and it worked - the LED blinks a lot slower now.

problem is AVRDude will no longer connect to the chip.

the chip is an ATTiny25, and the programmer is a USBTinyISP.

AVRDude has -B and -i parameters so I figured that 1Mhz/32Khz is about 32 so I put that in as the -B parameter, the -i parameter and, in desperation, both. No love. I tried some other numbers as well, 64, 128, etc.

Can you please steer me in the right direction to connect to the chip at 32Khz?

Thanks,

DougM

Please note that I have cross-posted this to AVRFreaks, so if I get an answer there I'll cross-answer my own question here and vice versa.

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dougm
 
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Re: newbie - changed CKSEL and now programmer won't connect

Post by dougm »

Answering my own question here, turns out that if usbTinyISP is running at 8Mhz then the number should be 256 and...

avrdude -c usbtiny -p t25 -B 256

boom!

But if anyone has time, what is the difference between -i and -B?

Thank you,

DougM

mtbf0
 
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Re: newbie - changed CKSEL and now programmer won't connect

Post by mtbf0 »

dougm wrote:But if anyone has time, what is the difference between -i and -B?
i think -B sends a delay parameter to a programmer with some local intelligence, whereas -i specifies a delay on the host for bitbang interfaces like dasa or parport.

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