Powering LED's from pins 39, 9, 10, 11? We did it before... now we can't!?

Started by BenIndustries, December 08, 2023, 10:09:16 PM

Previous topic - Next topic


Greeting to all - thanks in advance for any insight to our question.

We're prototyping a consumer electronics product and are somewhat new to the ESP32 world. We have build a couple of working prototypes using various ESP32 dev boards (KEEYEES amazon specials) and successfully powered several LED illuminated switches using all of these pins.

However - we like the LiPo solution available on the Olimex boards and have bought a bunch. But we can't get any voltage on the GPIO pins; 39 (Maybe because of the charging circuitry?) or pins 9, 10, and 11. I have noticed the many mentions of these latter pins being not available for use in several posts - and that it's an Espressif thing - not a shortcoming of the Olimex dev board topology.

But I'm not sure how "Not available" these pins are. All we need is 3+V on them and we have boards running that way now.

Can anyone help us understand what might be different in the Olimex versions and how to get our LED lit up?




You didn't mention exact Olimex boards you have. Tell me which ESP32 boards exactly do you have (full name as in our web-site, board + board variant) so I can be more specific.

One thing I immediately see is that you mentioned GPI039, but GPIO39 in our schematic is named "GPI39" - this is not by accident. It can never be output regarding the ESP32 module, it is only input for the ESP32. So it can't toggle LED but it can be useful as input.

Also GPIO9, GPIO10, GPIO11 are used for the built-in SPI flash, they are there only for measuring purposes. These are very unavailable - you can't have user software without flash memory, so these shouldn't be used at all.

Let me know if you have other specific questions.
Technical support and documentation manager at Olimex


That's helpful insight and really appreciated!

For clarity, we have the ESP32-DevKit-Lipo Rev. D - your part# 93658.

Can you confirm that it's your specific dev board that prohibits use of 09, 10 and 11 and not ALL ESP-32 dev boards? Because our current prototype is running fine on a KEEYEES ESP-32 dev board running LED illumination for our switches from all those pins.

Thanks for this confirmation.



It depends on the ESP32 module used. Our base ESP32 boards use ESP32-WROOM-32E which is official modules made by  Espressif systems. So you Google it and find this document:


and at the bottom of table 2 you see this note:

Pins GPIO6 to GPIO11 on the ESP32-D0WD-V3/ESP32-D0WDR2-V3 chip are connected to the SPI flash integrated on the module and are not led out.

This is also visible in our schematic and written on the processor (it says pins 6-11 are connected to the SPI).


Also pin 34 is not only input but the button is connected to it.
Technical support and documentation manager at Olimex