Programming a Tiny85 with Reset disabled

Other Hardware 3rd Party Boards
1

I'm using a Pololu 5V programmer (and also have a mk2 USB AVR programmer available) programming using avrdude from Linux.

I've programmed a Tiny85 to disable Reset with the fuses. Hower, as soon as I do, it stops reading commands from the programmer, and I can't "recover" it. Presumably this is because the programmer has to hold it in reset to issue the ICSP commands over SPI.

Can I recover this chip out of the "deaf" mode it's in, using the tools I have available?
If not, what tools would I need to do so? (The chip is $1.29, so it's not a big loss, but I'd like to learn something from all this :slight_smile:

2

I didn't realize disabling Reset would have that effect, but it makes sense. ICSP programming requires it to be held in reset, as you acknowledge.

I think you are going to need the high-voltage programming method. The AVR Dragon would do it, and it isn't particularly expensive. Mind you, you could get about 30 or 40 ATtiny chips for the same price.

There are "unbricker" boards which are cheaper, but for the extra $30 or so you get the fully featured board (the Dragon) which will do SPI, high-voltage, and (as far as I know) debugWire debugging. I find the Dragon pretty convenient for Tiny programming. I put a ZIF socket onto it, and made up a "jig" that connects the wires in the correct way for a particular family of processors.

That particular photo was for the Atmega328. I made another one for the Attiny family. Saves a lot of mucking around with hookup wires.

Reverse side:

3

Of course, with the Tiny, there aren't as many wires. After all, there can't be more than 8 going to the chip, and maybe a couple of other jumpers.

4

Thanks for the answer!

Dragon, huh? I've been thinking about one for a while. Though spending $50 to save $1 isn't going to convince the wife just yet :slight_smile: