ESP32-POE Not working with POE

Started by kwhodge42, April 12, 2023, 09:49:20 PM

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Hi All,

I'm new with ardiuno style controllers and attempting too build a circuit that turns on and off GPIO pins from a basic web server. I want to power the device with POE.

I've managed too get the MAC address for the device, as well as power it on fine with connected via USB. After loading even the most basic code (just flipping GPIO pins on and off) I cannot get the board to start while connected to POE. I do not have USB and POE connected at the same time.

I tested the 5V output and get about .9V and then it discharges too about .35V and then jumps up too approx .9V again. This seems too be some type of cap discharge and charge, but not sure what the issue is.

Any help would be great. Thank you all!


It is probably something in the network equipment or the cable. What is the PoE switch, is it capable of providing 48V DC? Is the switch compliant with IEEE 802.3af?

By the way, I know you mentioned it but it is really important to have only either PoE power applied to the board or USB power applied to the board. Having both even for few seconds might lead to damage.

Technical support and documentation manager at Olimex


So i just used a poe tester on both a POE camera and the ESP-32. The Camera draws ~56V and works just fine on the switch.

The ESP-32 jumps from 52V to 3.9V and back again, every few seconds. I have no idea what is causing this switch, but that must be the reason I can't get any stable power to the board.

That being said, it seems the switch and network cable work correcty, and the switch is IEEE 802.3af complaint. I also tested with different cables and got the same results.


1. Do you have anything other connected to the board? Even a LED connected to improper pin can influence the bootstrap sequence. Make sure to test with just the Ethernet cable.

2. Where exactly do you measure 52V and 3.9V?

3. Can the board still be programmed via USB?
Technical support and documentation manager at Olimex


Nothing else is connected.

I measured 52 and 3.9V on my POE tester.

The board can still be programmed via USB.

I tried using a POE injector, and the board seems too work just fine. I assume it's the POE switch not sending power over every pair and the board doesn't check every pair.

I'll use a POE injector too run the project from now on. Thanks for the help!


I think probably something in the settings in the switch. Maybe ESP32-POE consumes too little current and switch sleeps it, maybe some other option. I'd check the documentation of the switch.
Technical support and documentation manager at Olimex