# Suddenly failing to upload ATTiny85 **URL:** \ **Category:** Uploading\ **Created:** [March 10, 2026, 12:18pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623 "2026-03-10T12:18:51Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Terrypin](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@Terrypin](https://forum.arduino.cc/u/Terrypin)\ **Post date:** [March 10, 2026, 12:18pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/1 "2026-03-10T12:18:51Z")
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](https://azduino.com/bin/micronucleus/micronucleus-cli-2.5-azd1-i686-mingw32.tar.bz2)" ---
**Author:** ![Brazilino](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/brazilino/32/1198404_2.png) [@Brazilino](https://forum.arduino.cc/u/Brazilino)\ **Post date:** [March 10, 2026, 12:36pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/2 "2026-03-10T12:36:03Z")
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. ---
**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\ **Post date:** [March 10, 2026, 1:55pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/3 "2026-03-10T13:55:14Z")
> [@Terrypin](#): > > Uno as ISP If this is "permanently" on a solderless breadboard, "clean and reseat" the capacitors, especially the 104 reset cap with thin legs. ---
**Author:** ![6v6gt](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/6v6gt/32/225488_2.png) [@6v6gt](https://forum.arduino.cc/u/6v6gt)\ **Post date:** [March 10, 2026, 2:34pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/4 "2026-03-10T14:34:36Z")
> [@Terrypin](#): > > I frequently use Uno as ISP to program ATTiny85 chips and all was well two or three days ago. 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. ---
**Author:** ![Terrypin](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@Terrypin](https://forum.arduino.cc/u/Terrypin)\ **Post date:** [March 10, 2026, 3:31pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/5 "2026-03-10T15:31:55Z")
Yes, three chips so far. AI's latest says "_... the Spence Konde server ([azduino.com](http://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](http://azduino.com)** refused to connect. ERR\_CONNECTION\_REFUSED ---
**Author:** ![Terrypin](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@Terrypin](https://forum.arduino.cc/u/Terrypin)\ **Post date:** [March 10, 2026, 3:33pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/6 "2026-03-10T15:33:37Z")
Thanks @Brazilino. Don't think either of those is the cause in this case. ---
**Author:** ![Terrypin](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@Terrypin](https://forum.arduino.cc/u/Terrypin)\ **Post date:** [March 10, 2026, 3:35pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/7 "2026-03-10T15:35:34Z")
Thanks, clutched that latest straw but no joy. ---
**Author:** ![Terrypin](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@Terrypin](https://forum.arduino.cc/u/Terrypin)\ **Post date:** [March 10, 2026, 3:40pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/8 "2026-03-10T15:40:27Z")
Anyone else using that? With similar problem? ---
**Author:** ![ptillisch](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@ptillisch](https://forum.arduino.cc/u/ptillisch)\ **Post date:** [March 11, 2026, 5:10am UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/9 "2026-03-11T05:10:39Z")
Hi @Terrypin. > [@Terrypin](#): > > 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. 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. > [@Terrypin](#): > > I tried to reinstall the previous core, 1.5.0, instead of the current 1.5.2 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. ---
**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\ **Post date:** [March 11, 2026, 2:26pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/10 "2026-03-11T14:26:08Z")
Parallel conversation here... > [@Attiny by SpenceKonde](https://forum.arduino.cc/t/attiny-by-spencekonde/1434789/): > > Hello! Please help me, I have no idea how to install attinycore by spencekonde, their server seems to be down, I tried some github/sourceforge installs but I never sucseeded and kept getting errors, chatgpt couldn't help me as well. I am using arduino uno R3 as ISP for Attiny85. I need exactly attinycore by spencekonde because I need to turn on B.O.D which I cant do with other cores. Any help is apreciated, any other method is appreciated, ask questions, I will try to do what u say from blank li… ---
**Author:** ![Terrypin](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@Terrypin](https://forum.arduino.cc/u/Terrypin)\ **Post date:** [March 11, 2026, 8:44pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/11 "2026-03-11T20:44:21Z")
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. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [September 7, 2026, 8:45pm UTC](https://forum.arduino.cc/t/suddenly-failing-to-upload-attiny85/1434623/12 "2026-09-07T20:45:08Z")
Closed on September 7, 2026, 8:45pm UTC This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.