Connect two embedded devices with USB host with Ethernet?
There is one variant with a minimal hardware, if you are (self, or friending) a brutal embedded low-level system programmer.
DISCLAMER: I never checked this in practice, it's all about theoretical speculation.

First and simple, connect the MCUs directly via the USB transceiver interface lines (D+ &amp; D-) providing the respecting static voltage levels necessary to properly detect the mode (full speed or high speed) of the bus, by the appropriate pull-down resistors.


Second and complex, program the OHCI/EHCI unit of the MCU and the responsible driver to only send/receive &quot;naked&quot; USB data type packets and eliminate all other activities.


As a result, you'll (probably) get a half-duplex channel controllable by something like CDMA/CA (i.e. Collision Avoidance) access method employed in wireless networking.

There is another variant with stronger hardware but standard software.

Use a pair of USB FIFO ICs (like FT245R or FT232R in FIFO mode because it has a clock output) controllable by a low-cost CPLD.



As a result, you'll get a full-duplex channel controllable by something like PPP.