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Topic: ATTiny85 arduinoisp problem (Read 10 times) previous topic - next topic

Coding Badly

I had the auto reset disabled, but then I get sync errors.  So I unplugged the reset wire, and still had issues,

You will.  Autoreset has to be disabled or the Arduino will not function as an ISP.

i have to hold the reset button on the uno and then let go when avrdude tried connecting to get anything now...

In which case, the bootloader is responding.

Give these a look...

I've found a few places that recommend a 110 ohm resistor.  Try that.


Jan 30, 2011, 07:52 am Last Edit: Jan 30, 2011, 07:55 am by 92_foxgt Reason: 1
lol... correct me if im wrong...To disable the auto reset I'm using two 220 ohm resistors in parallel, but that is when I get the sync errors. Two 220 ohm resistors in parallel is equivalent to 110 ohms... 1/(1/220 + 1/220).

I looked through those posts... I hadn't thought about putting a cap as well as the 5v to it... I'll try that as well and see if it helps me get around the sync errors I guess

edit: oops, thought I mentioned the 220 ohm resistors earlier, added that


If you have a serial cable with a level shifter (i.e. MAX232) you can just use that. Sine you only connect the Tx & Rx to the Arduino you will not get the reset. The ArduinoISP won't work if it resets when you load the sketch into the ATtiny. (Maybe you know that or am doing something else, reading this I'm a little confused.)
"Data is not information, information is not knowledge, knowledge is not understanding, understanding is not wisdom."
~ Clifford Stoll


Sorry, I understand that it won't work properly if the uno resets, but with the uno's reset pin tied to power(haven't tried the cap idea) through a 110 ohm resistor I get sync errors and can't communicate with the chip at all. When I use the manual reset button and avrdude I can get it to communicate but it shows the wrong device ID. There is a post on the arduinoisp page saying that it wont work with an arduino uno due to the optiboot or something... I saw someone else mention it. Has anyone worked around it? I have a breadboard arduino and an FTDI breakout cable but the last time I messed with this(like 2 am one night) it was giving me some other error and I just went to bed. School has been keeping me busy all week until I go to bed, so I haven't been able to put much time in this, especially since the Tiny85 isn't critical towards my projects, just a side thing I was toying with.

Coding Badly

haven't tried the cap idea

That is the next step.

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