Booting Omega from PoE shortens components

thomasderbauer — Thu, 22 Dec 2022 07:33:21 GMT

Hi Onioneers!
I am building a project with stacked PCB's. The first PCB contains the Omega2S+ and a CP2102 for Serial Connection. Second PCB contains RJ45, PoE and PSU Components.
When Connecting only the second PCB to my Switch with PoE the 3V3 LED lights up and I can see in my switch that PoE is detected correctly and it's pulling about 0.9W.
I then combined the two PCB's together and used USB to my PC to create a Serial Connection (No Ethernet connected). In this case the 5V of the USB goes to the 5V Rail on the PSU PCB and gets regulated down to 3V3 to supply the omega.
I then connected Ethernet with a non PoE port. It gets detected and I could ssh into the omega and worked for 20 minutes on it. I then unplugged the USB Cable and plugged the Ethernet into a PoE Port. This led to the board shorting all components. I had to replace CP2101, Omega and both Voltage Regulators. What I'm not sure is why this doesn't happen on the USB but with the PoE.
I attached the two schematics. The boards are connected via the 10pin connector.
Any Hint or Idea what could cause this would be greatly appreciated.

Starting up Omega2S on custom PCB

thomasderbauer — Tue, 22 Nov 2022 02:49:45 GMT

That makes Sense, so my Power Wiring should be correct. I see that in your schematic and in the datasheet the HW Reset and VDD_FLASH are connected via transistors. Any Benefit to that compared to just pulling them to GND via a Switch? CPU_RST_SWITCH simply bridges to GND.

Topics tagged with cp2102

Booting Omega from PoE shortens components

Starting up Omega2S on custom PCB