I'm attempting to add an RJ45 Ethernet jack to a commercial device without one by replacing an embedded WiFi module, which, according to its datasheet, is connected to the rest of the system as follows:
The section labeled "PHY" here is a PHY on the device (on a Micrel Ethernet switch chip elsewhere on the board), while the section labeled "HF-A11-SMT" is the WiFi module I'm attempting to replace with an ethernet jack.
I'd like to be able to connect the jack directly to a regular ethernet port on a computer, so I need some way to add a jack and magnetics, or a MagJack-equivalent, to the board without modifying any of the circuitry supposed to connect "transformerless" to the WiFi module.
There's plenty of examples out there for how to hook up a MagJack if I was able to remove the "transformerless" circuitry in the schematic above and connect directly to the Micrel chip, but since I haven't been able to fully trace this part of the board (it's quite a complicated design, and there's a lot of other unrelated stuff around this module that make trying to trace it difficult) and I'd like to interfere with the rest of the device as little as possible, I'm looking for a way to connect a regular RJ45 jack with magnetics to the pads meant for the WiFi module's RX/TX pins ("transformerless" circuitry intact).
I can't find any information on how adding a jack to a design like this might work. If there's either a circuit that could do this which I could design a simple board for, or some sort of off-the-shelf version of the same for testing devices like these, what are they? If not, what's the minimal amount of modification that would have to be made to the "transformerless" circuitry in order to make this feasible?