Changing fuse settings; USBtinyISP vs. STK200 (PonyProg)

USB AVR Programmer and SPI interface. Adafruit's USBtinyISP.

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cameron_kerr
 
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Changing fuse settings; USBtinyISP vs. STK200 (PonyProg)

Post by cameron_kerr »

I have just finished building my USBtinyISP, and was able to query a BANNED ATtiny13 just fine, but I also have a bunch of ATmega8 parts that were set to use an external crystal originally, and I wanted to change their fuse bits back to default for another project (internal oscillator @1MHz). Previously the fuse bytes were 0xC9FB, and I wanted to change them to 0xD9E1, which are the defaults according to the ATmega8 data-sheet (page 223)

I tried to use my USBtinyISP with avrdude 5.5 on Mac OS X, but it resulted in a init=-1. (This was before I then verified my programmer using an ATtiny13).

Edit: I built the programmer from a kit.

I eventually went away and scrounged an old PC and put Linux on it, and used an old parallel port bootstrap programmer (-c stk200), and in the same circuit it worked and I was able to change the fuse bits successfully.

I then took the part out and plugged it into an empty breadboard whereby I could then get avrdude to work with it successfully using my USBtinyISP.

So, my question then, is why does a STK200 succeed in changing the fuse bits when my USBtinyISP doesn't? Is it perhaps one of those cases where I need to short R6 and R7?

I wonder if a STK200 is classed as a high-power programmer? (No, the RSTDISBL fuse hadn't been changed from default).

My other question, is what do you do when you don't know what clock settings it was previously used with?

Thanks. I've enjoyed this project so far... my first significant project (that works) :D Now I can get on and get my main project prototyped.

adafruit
 
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Post by adafruit »

i dont know for sure what the stk200 is but if the fuses are set to "external oscillator" then you need to use "high voltage" or "parallel" programming, not serial as the USBtiny does. those programming methods do not require the chip to have a crystal on it since it overrides it
in general, you just have to be careful when setting fuses!

cameron_kerr
 
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Joined: Fri Apr 04, 2008 12:32 am

Post by cameron_kerr »

The stk200 is essentially a parallel plug with some of the wires from the solder cups being fed, through resistors, straight into the pins of the µC, and is programmed over SPI.

So basically, I need to keep around something with a parallel port? Or is there a nice cheap (DIY?) USB programmer that would suffice? Can the USBtinyISP be used in such a way?

adafruit
 
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Post by adafruit »

in theory the usbtiny does eveything an stk programmer can do but since i dont have your setup in front of me, there could be something else that happened that made one work and not the other.

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