PoE (Power over Ethernet) is a standard that allows both data and power to be transmitted via a single Ethernet cable. The ESP32-PoE2 from Olimex is a board compliant with this standard, offering two types of connectivity: wireless (Wi-Fi) and wired (Ethernet, via the LAN8720 chip). It is this board that I would like to showcase here.
The ESP32-PoE2 is an open-source and open-hardware project from Olimex. The full project sources (including the PCB in KiCad) are available on GitHub . I bought my unit for 120 zł. I chose the version with extra memory, i.e. the one based on the ESP32-WROVER-E-N4R8 with 4 MB Flash and 8 MB PSRAM.
The TPS2378PW provides PoE power and complies with the IEEE 802.3 standard. An input voltage of at least 37 V is required. The board itself is capable of powering external circuits – it has 24 V / 0.75 A or 12 V / 1.5 A, as well as 5 V / 1.5 A and 3.3 V / 1 A, with a total output power of up to 25 W.
Note: The ESP32-POE2 does not have galvanic isolation from the Ethernet power supply, which may cause ground loops. When programming via USB, disconnect the Ethernet cable (if PoE is active). Connecting an external power supply may be dangerous – it is recommended to use the Olimex USB-ISO to protect your computer and the board.
Additional peripherals include a microSD card slot, a built-in USB-to-UART converter for programming (CH340), a BL4054 controller for working with LiPo batteries, and a wide range of connectors, including Olimex’s UEXT.
Schematic:
The board is programmed in PlatformIO, and I’ll demonstrate a few examples within this environment.
Hello World LAN8720
The LAN8720 is what makes this board stand out the most, and that is what I will focus on here. First, platformio.ini – the PIO libraries already have a profile for this board (esp32-poe-iso), and there is also a ready-made library for the LAN8720.
[env:esp32-poe-iso]
platform = espressif32
board = esp32-poe-iso
framework = arduino
monitor_speed = 115200
build_flags =
-D ETH_PHY_TYPE=ETH_PHY_LAN8720
-D ETH_PHY_ADDR=0
-D ETH_PHY_MDC=23
-D ETH_PHY_MDIO=18
-D ETH_PHY_POWER=12
-D ETH_CLK_MODE=ETH_CLOCK_GPIO0_OUT
-D BOARD_HAS_PSRAM
-mfix-esp32-psram-cache-issue
In the main source file, main.cpp, you need to include the ETH.h header; you can then add a callback to handle events, and even connect a socket to the target host. This will allow you to check whether connectivity is available:
Code: C / C++
Log in, to see the code
I checked the response for the domain name google.com – the connect function automatically converts it to an IP address.
Result:
ets Jul 29 2019 12:21:46
rst:0x1 (POWERON_RESET),boot:0x1b (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0030,len:184
load:0x40078000,len:12680
load:0x40080400,len:2908
entry 0x400805c4
Olimex ESP32-POE2 Ethernet Test (v2.x compat)...
ETH Started
ETH Connected
ETH Got IP
ETH IP: 192.168.0.137
Connecting to google.com
HTTP/1.1 301 Moved Permanently
Location: http://www.google.com/
Content-Type: text/html; charset=UTF-8
Content-Security-Policy-Report-Only: object-src 'none';base-uri 'self';script-sr
c 'nonce-rvcm1L9GDkZjYCPWad4kQw' 'strict-dynamic' 'report-sample' 'unsafe-eval'
'unsafe-inline' https: http:;report-uri https://csp.withgoogle.com/csp/gws/other
-hp
Date: Thu, 29 Jan 2026 18:19:25 GMT
Expires: Sat, 28 Feb 2026 18:19:25 GMT
Cache-Control: public, max-age=2592000
Server: gws
Content-Length: 219
X-XSS-Protection: 0
X-Frame-Options: SAMEORIGIN
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<
TITLE>301 Moved</TITLE></HEAD><BODY>
<H1>301 Moved</H1>
The document has moved
<
A HREF="http://www.google.com/">here</A>.
</BODY></HTML>
Closing connection
The board successfully obtains an IP address via DHCP from the router, and is then able to convert the hostname to an IP address and send a simple HTTP packet there. The response is also received; we can see here that Google is attempting to redirect us. The ESP also appears in the router’s list of DHCP clients.
HTTP server
I was also wondering whether it was possible to do the opposite – not establishing a connection, but waiting for one. So I set up a simple server that listens on port 80 (HTTP) and receives packets via the LAN cable:
#include <Arduino.h>
#include <ETH.h>
#include <WebServer.h>
#include <WiFi.h>
WebServer server(80);
static bool eth_connected = false;
// In v2.x, the event handler uses WiFiEvent_t and the signature is slightly
// different
void onEvent(WiFiEvent_t event) {
switch (event) {
case ARDUINO_EVENT_ETH_START:
Serial.println("ETH Started");
ETH.setHostname("esp32-ethernet");
break;
case ARDUINO_EVENT_ETH_GOT_IP:
Serial.println("ETH Got IP");
Serial.print("ETH IP: ");
Serial.println(ETH.localIP());
eth_connected = true;
server.begin();
Serial.println("HTTP server started");
break;
case ARDUINO_EVENT_ETH_DISCONNECTED:
Serial.println("ETH Disconnected");
eth_connected = false;
break;
case ARDUINO_EVENT_ETH_STOP:
Serial.println("ETH Stopped");
eth_connected = false;
break;
default:
break;
}
}
void handleRoot() {
String html = "<!DOCTYPE html><html><head><title>ESP32-POE2</title>";
html += "<style>body { font-family: Arial; text-align: center; margin-top: "
"50px; }";
html += "h1 { color: #0066cc; }</style></head><body>";
html += "<h1>Hello World from ESP32-POE2!</h1>";
html += "<p>Ethernet connection is stable and server is running.</p>";
html += "<p>Uptime: " + String(millis() / 1000) + " seconds</p>";
html += "</body></html>";
server.send(200, "text/html", html);
}
void setup() {
Serial.begin(115200);
Serial.println("Olimex ESP32-POE2 Ethernet Test (v2.x compat)...");
WiFi.onEvent(onEvent);
server.on("/", handleRoot);
// PHY address: 0
// Power pin: 12
// MDC pin: 23
// MDIO pin: 18
// PHY type: ETH_PHY_LAN8720
ETH.begin(0, 12, 23, 18, ETH_PHY_LAN8720, ETH_CLOCK_GPIO0_OUT);
}
void loop() {
if (eth_connected) {
server.handleClient();
}
}
The libraries handle everything – the server is accessible without Wi-Fi:
Summary
This is undoubtedly an interesting board, especially if you intend to use PoE. The inclusion of PSRAM is also a plus. What’s more, it’s all very easy to get up and running – there are ready-made libraries available, so all you need to do is configure the pins. I had no trouble mapping wired Ethernet to an HTTP server or establishing a connection with the outside world.
I haven’t tested PoE itself, as I don’t have a suitable power supply, but I may well come back to that.
Have you used PoE in your projects yet? Do you see potential for a board like this?
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