Octopi (PI4) for UART passthrough to connect Marlin and TFT35?

Get Help
1

This is not an issue per se but rather an idea.

Basically I have an Ender 3 pro with SKR mini E3 V2.0 motherboard on Marlin, a Bigtree TFT35 E3 V2.0 screen and Raspberry PI 4 running Octoprint.

Right now I am using the following setup:

Pi4 --> Marlin (via USB)
TFT35 --> Marlin (via TFT pins on motherboard)

The setup works fine except for I'd like to: 1) eliminate USB connection; 2) Continue to use TFT35 with touch mode and ideally let Octopi talk to TFT35 to sync status.

I came across this thread on github: https://github.com/bigtreetech/BIGTREETECH-TouchScreenFirmware/issues/281, which proposes a solution to connect PI->TFT->Marlin. The solution solves my problem but apparently there are some lagging issues as TFT is in the middle handling the Pi <-> Marlin traffic.

Given that PI4 has 5 PL011 UARTs, I am wondering if it is possible to have Marlin<->Pi<->TFT passthrough. Is this physically feasible? It looks like hooking two UARTs on Pi and forward signals is possible but I would assume there are more than that (e.g., what if Pi and TFT talks to Marlin in the same time).

I just like to ask around and see anyone has some insight on the feasibility of this idea.

2

It is far past my abilities to achieve something like this but it doesn't seem to me like it would be impossible given the know-how.
It would be very handy to have the tft 35 or equivalent be able to have a 3rd mode along with the touch screen and marlin mode which acts as an octoprint mode.

Some one has to do this at some point right?