TL;DR version: it would take too long to come up with a useful firmware mod. I'm missing the toolchain, complete source code, compilation instructions, libraries, hardware architecture, ...
In the meantime, I did take the TV apart to fix a broken stand-off.
I cannot see any immediate serial (RS232 or TTL) connections and I did not bother probing for some. I image if any would exist they would come out of the main [MStar] CPU. As such, it's more likely the serial is NDIS-based on production units. There's also the possibility that some pins from VGA or other ports might be repurposed as serial ports upon some special boot sequence. However, the strongest possibility is that I've missed those pins.
The unit is split into several parts:
- MStar processing board that takes care of all inputs (HDMI, USB, Ethernet, ...) and raw LCD output
- Samsung LCD panel board - big custom ASIC handling the LCD output, probably from a standard LVDS input
- IR input and output, ambient sensor and status LED board
- backlight power supply board - I think the TV has either 16 or 16x16=256 LED backlight panels
- main power supply board
From now on it's mostly picture-driven, click on the pictures for the full uncut version.
Heatsink removed. The main chip is an MSD388USV-V6 - MStar branded, no data.
The firmware is also MStar branded, I suspect they are using their SDK under an NDA.
Backside of computing board:
Backlight(?) power supply, cover on:
Backlight(?) power supply, cover off:
Infrared receiver, ambient light sensor, 3D IR transmitter, status LED. Backside:
Samsung branded LCD Panel driver board:
Main power supply: