Schematic PDFs are now available on the main project page if you want to see what makes this thing tick!

The ESP32-Prog-1.pdf file documents the ESP32 programming submodule.  It's a straightforward CP2102N based design with automatic EN and IO0 control circuitry, optimized for size by using TVS, transistor and resistor arrays instead of discrete components.  Note that pullups for EN and IO0 and the EN capacitor are not on this board but on the main board instead, since they need to be present on the main board whether the programmer is connected or not.

The wESP32-1.pdf file has the main board schematic, and there's much more to that one.  The top left has the Ethernet jack and phy, below that is the PoE power supply, top right is the ESP-WROOM-32 module, below that the EN and IO0 control circuitry and on the bottom right the 3.3V buck converter and 20-pin IO header.

The Hanrun HR861153C Ethernet jack has LEDs, magnetics, Bob Smith cable terminations and PoE diode bridges built-in, and this high level of integration is very helpful in keeping the board compact.  The phy is a LAN8720A connected to the ESP32 via RMII, with resistor straps configured for full 10/100 capability.

The PoE power supply is optimized for 12V output (with 5V optional), and is based on the highly integrated Si3404-A PoE PD and PWM.  It is configured in a fully isolated flyback topology.  You may note that some component values are missing here, specifically those related to loop compensation and snubbers.  The reason for this is that these values have to be optimized based on measurements that can only be obtained once I have working prototypes, as they are very dependent on flyback transformer and layout parasitics.  It is likely that not all these components are needed, but experience with my other PoE project has taught me that it's better to allocate space for all components that might be needed than to regret not having them.  I added a lot of filtering on the secondary side to improve my chances of having nice and clean power, since I witnessed quite a lot of noise on my other PoE project.  A simple buck converter rounds out the power system to generate the 3.3V for the ESP32, phy and other connected circuitry.

The EN/IO0 circuitry is modelled after that on the Olimex ESP32-GATEWAY and is needed because of the many possible states of the IO0 line.  It needs to work correctly to trigger programming mode or UART terminal on boot, and it is also used as the clock input for the Ethernet MAC so this clock has to be activated after the ESP32 has determined boot mode.