Transparent Wi-Fi module with RMII input

[kendall]

I need to convert a Ethernet-connected embedded project with wireless connection.

I'm looking for a low-cost (main constraint, less than USD $15) and most open-source/-hardware possible Wi-Fi bridge module, like Vonets.

It need to behave transparent, redirecting all network frames (transport layer) to existent-and-already-stable IP stack implemented at current ETH hardware with minimal firmware modification; if possible, using existent RMII pins.

My first attempt was with ESP8266, but there's some very painful challenges:

I couldn't just change transceiver and RJ-45 with it, because it's communication is UART-based (some module variants support SPI). To workaround that, I tried enabling PPPoS to communicate uC<->ESP8266, then sending data through ESP's built-in IP stack and forwarding it to Wi-Fi adapter and then to Internet.
However, although it's LwIP port had PPP_SUPORT #define's at source code (which seems to be added in a recent release v1.4.0 from March-2016), there's no documentation about enabling it and it's usage. Furthermore, IP forwarding also seems not be supported between virtual interface (e.g. ppp0) and "real" interface (e.g. wlan0).

Do you suggest some other hardware to do the "Wi-Fi bridge" job? Should ESP32 the solution to convert RMII signals?
In the case of keep using ESP8266, there's another protocol or way to made it transparent?

[ESP_Sprite]

Fyi, we have both Ethernet (RMII) as well as WiFi on the ESP32. We do not have support for packet forwarding yet (which is what you seem to need) but we do have that in the roadmap; it should appear in esp-idf eventually.

[a2retro]

Hi about one month ago ESP_igrr gave an estimate of 3 weeks for a reference release for the Ethernet PHY design. May we have a revised estimate of when that may be released?

Thanks

[ESP_igrr]

The design of the board was finished some time ago, not sure what's preventing it from being published. Will ask after the weekend.

[a2retro]

@ESP_igrr Thanks for the update. I went and ordered some TLK110's in anticipation.

[a2retro]

@ESP_igrr any word on the Ethernet reference design? My TLK110's arrived today

[ESP_Sprite]

We're still working on it. The reference design includes PoE as well, but the engineers are having some trouble bringing that up. As soon as we have a working and tested design, I'll see if I can post the schematics.

[a2retro]

@ESP_Sprite Appreciate the update. While PoE not something I am looking at for the short/mid term, I can understand why the team would want to hold off and include it.

[a2retro]

Is this reference design an add on to one of the existing dev kits or an all in one design?

[ESP_Sprite]

It's a new design.