Ethernet Controller Overview
Thought for 10 sec
This is a W5500 Ethernet controller reference design with PoE-related power circuitry.
In plain English: it lets another controller, like an Arduino, STM32, ESP32, or Raspberry Pi header, talk to a wired Ethernet network over SPI. The W5500 handles the Ethernet protocol/PHY side, the RJ45 connector connects to the Ethernet cable, the 25 MHz crystal clocks the Ethernet chip, and the AMS1117-3.3 regulator generates the 3.3 V rail for the W5500 and logic.
Diagram
Key blocks:
- J3 barrel jack / +12V rail: external DC input.
- U2 AMS1117-3.3: converts input power down to 3.3 V.
- U1 W5500: Ethernet controller with SPI interface.
- J1 RJ45 connector: physical Ethernet port.
- J2 2x4 header: exposes SPI/control signals like SCLK, MOSI, MISO, SCS, RST, and INT.
- X1 crystal + capacitors: provides the clock needed by the W5500.
- LED/resistor networks: link/activity/power indication and Ethernet termination/biasing.
One important note: the project description says “PoE” and “can be used as PoE injector,” but from the visible component list this looks more like an Ethernet/W5500 board with 12 V input and RJ45 circuitry, not a complete standards-compliant IEEE 802.3af/at PoE injector or powered-device supply. A real PoE injector/PD usually needs dedicated PoE magnetics, detection/classification, isolation, and power-path circuitry.
Check PoE nets
ESP32 wiring
Check W5500 support
Review PoE BOM
Explain power path
