A credit thank you to GL Gough Lui for providing the configuration details required to get the lower circuit working.
The vendor alluded to the requirement for a lan7800 driver. When the interface didn't work initially, I thought the driver wasn't supported in the Raspberry Pi Operating System (O/S). Microchip PoE to USB-C Power and Data Adapter RoadTest Review Data After much testing, I became convinced a missing driver wasn't the issue and the interface wasn't being detected. I went as far as to load an ARM version of Ubuntu to prove out my understanding.
After multiple attempts to resolve the issue, I made an appeal to the E14 Community.Insight into lan78xx driver support for Pi to seek a solution. GL's response provided the solution and the source of knowledge that helped him solve the issue.
GL solution worked with no requirement for additional cables mention in his post.
Here are the configurations details to establish the configuration shown in the drawing above.
add after rootwait
After reboot a usb# interface will appear using the ip a command. Configure an IP address on the interface in the file /etc/dhcpcd.conf
After reboot a eth# interface will appear using the ip a command. Configure an IP address on the interface in the file /etc/dhcpcd.conf
With an IP address established on the interface, ssh can be used to make a connection.
NO, THAT IS NOT COMPLETELY ACCURATE
Using the term “working” as it relates to technology has been a love hate relationship for me. After spending hours trying to resolve a problem I issue few simple tests to confirm it’s “working”, to discover later it actually isn’t “working”. Hey, wait a minute, I’m positive I got results! I soon discovers that the simple tests are not sufficient to define working.
I discovered that the trifecta of simple tests, an Interface appears and the Interface sports an IP address and you can ping it, doesn't mean it is working. Using the two circuit shown at the beginning of this post only one configuration works. That working is at a reduced bandwidth, documented in this post Microchip PoE to USB-C Power and Data Adapter RoadTest Review Data Revisited
PiZeroW, Pi3B & Pi3B+ does not provide an Ethernet Interface with
otg_mode=1 in /boot/config.txt
Pi4B does provide an Ethernet Interface with
otg_mode=1 in /boot/config.txt
the interface can be connected to over a network
PiZeroW, Pi3B & Pi3B+ provides an usb0 Interface but cannot be assigned an IP address
Pi4B does provide an usb0 Interface and can be assigned an IP address with
the interface can not be connected to over a network. If the Pi4B is sporting a working Ethernet interface and you ping the usb0 interface, the Pi will respond to the pings. Remove that working Ethernet interface and you discover there are no ping replies.
The results of this testing is not a reflection of the Microchip PoE USB-C device performance. This is all Raspberry Pi related. I'm sharing the details here to consolidate my testing data and to list what I discover works and what doesn't work.