Suddenly failing to upload ATTiny85

Development Tools Uploading
1

I frequently use Uno as ISP to program ATTiny85 chips and all was well two or three days ago. But yesterday and this moning it has failed at every attempt.

Tests are all with Blink and I've tried the obvious things. Beginning to suspect something to do with the aTTiny core. So I asked Google AI, and after a while read this:

"Since you have ruled out the hardware basics (wires, capacitor, chip, Uno itself),your suspicion about the ATtiny Core is highly probable. In early 2026, users reported specific instability with automatic updates to the ATTinyCore (Spence Konde) and Arduino IDE 2.x.

I tried to reinstall the previous core, 1.5.0, instead of the current 1.5.2 (whree is 1.5.1?) but got "Error downloading https://azduino.com/bin/micronucleus/micronucleus-cli-2.5-azd1-i686-mingw32.tar.bz2"

2

I’m not in front of my equipment, but the last time I faced something like this was due to the IDE “forgetting” my last setup.

On the IDE Menu, AttinyCore allows you to choose betweeen different Attinys 25/45/85. Sometimes my IDE changes from 85 to 25, which screws up memory issues and uploads.

Another possible problem happens if you’re trying to upload a sketch in a different clock frequency of the one you chose when burning the bootloader.

3

If this is "permanently" on a solderless breadboard, "clean and reseat" the capacitors, especially the 104 reset cap with thin legs.

4

Can you duplicate the problem on multiple ATTiny85 chips ? Clearly the idea is to determine if the problem is simply a single rogue chip or if it lies in the process/infrastructure to program it.

5

Yes, three chips so far.

AI's latest says "... the Spence Konde server (azduino.com) is down, which explains why your core is in a broken "zombie" state.
Since you've swapped every piece of hardware and tried two IDE versions, we have to treat the ATTinyCore files as corrupted."

I tried that site and see this:

This site can’t be reached

azduino.com refused to connect.

ERR_CONNECTION_REFUSED

6

Thanks @Brazilino. Don't think either of those is the cause in this case.

7

Thanks, clutched that latest straw but no joy.

8

Anyone else using that? With similar problem?

9

Hi @Terrypin.

Please provide a detailed description of what you mean by "failed".

Provide the full and exact text of any error or warning messages you encountered.

That is a waste of time. Focus your energy on fixing the actual problem instead of getting distracted by trying to install an outdated version of the package as a futile attempt at a workaround.

10

Parallel conversation here...

11

I've made progress in the almost two days since my last post and I think success is close. The main issue obstructing upload was an obscure port 'freezing'. Uninstalling a USB hub and other stuff eventually fixed it. I then methodically uploaded Blink to my three Tiny 85 chips successfully. Followed by my target sketch. The outstanding problem is 'simply' squeezing it into the Tiny85.

BTW, I had also tried that year old alternative .json at the stage I still suspected the culprit was similar to the year old issue re Spence Konde's licence.