I'm trying to get the ATtiny13A to run on 3.3V which, if I'm not wrong, would be possible.

I've programmed the chip using an Arduino Uno. I'm doing a simple blinking LED example and when I power the ATtiny with Arduino's 5V pin it works without any problem. If I power it with Arduino's 3.3V pin it does not light the LED.

This is my Arduino IDE's config when programming the ATtiny:

enter image description here

I've tried other configurations also.

Am I doing something wrong? Do I need to program it in a different way or do something else?

Edit to add more info:

I'm using this guide (or a similar one, don't exactly remember if it was that one). This is how the connections look like:

enter image description here

Red LED connected to pin 4 with a 220ohm resistor. Also, I've measured voltage on that pin 4 of the ATtiny when connected to 5V and it's outputting ~6V but 0V when connected to 3.3V.

  • \$\begingroup\$ Post schematic of LED connections to AtTiny. What color is the LED? \$\endgroup\$
    – MadHatter
    May 10, 2020 at 19:55
  • \$\begingroup\$ I edited to add more info. Thanks! \$\endgroup\$
    – JV Lobo
    May 10, 2020 at 20:05
  • \$\begingroup\$ Any chance your driving the pin as a input pull up instead of output? Also is the LED red? \$\endgroup\$
    – MadHatter
    May 10, 2020 at 23:09
  • \$\begingroup\$ Do you have a pull-up resistor on the reset pin? \$\endgroup\$
    – Etzeitet
    May 10, 2020 at 23:29
  • \$\begingroup\$ I don't have a pull-up resistor on the reset pin. Is this needed? I've just tried hooking up one in PB5 (reset pin according to the documentation) but it does no difference :/ \$\endgroup\$
    – JV Lobo
    May 11, 2020 at 10:40

1 Answer 1


Make sure your BOR settings are appropriate for a 3.3V supply.

enter image description here

  • \$\begingroup\$ I'm not sure I fully understand. The available BOD options are: disabled, 1.8, 2.7, 4.3, right? if I want it to work on 3.3V which one should I chose according to that table?? 2.7 or 4.3??? I've tried with the four of them tho and it still doesn't work :/ Do I need to burn the bootloader when I change these settings or not needed? \$\endgroup\$
    – JV Lobo
    May 11, 2020 at 10:51
  • \$\begingroup\$ Yes. If you change things like BOD or Clock Frequency, you need to hit burn bootloader. This will cause the necessary fuses to be set on the Tiny. BOD should be set to something below your normal operating voltage. It shuts down your Tiny if the voltage drops below whatever you set. A microcontroller can do funky things if VCC gets low - especially at higher clock speeds. It is probably safer to shutdown if VCC is low, and BOD let’s you do that. Then the Tiny will restart when voltage levels are restored. \$\endgroup\$
    – Etzeitet
    May 11, 2020 at 11:27
  • \$\begingroup\$ Generally you would use 10 or 01 if you want BOD but you should also ensure that the chip can operate correctly at the Min voltage. So, if you use 01 you'd want to make sure from figure 18-1 that the clock frequency is not too high for 2.50V. 9.6MHz is too high to be 100% sure. \$\endgroup\$ May 11, 2020 at 11:27
  • \$\begingroup\$ The 10 setting is useless in my opinion, because the chip is not guaranteed to operate at all below 1.80V and the BOD is not guaranteed to engage until 1.7V. \$\endgroup\$ May 11, 2020 at 11:29
  • 1
    \$\begingroup\$ that was my problem all the time... I was not re-burning the bootloader when changing that configuration 😭 now it WORKS! thanks a lot :) \$\endgroup\$
    – JV Lobo
    May 11, 2020 at 12:00

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