I've toyed with the idea of replicating its functionality on an Arduino, but ended up just buying the adapter :)
In the end, I'm not sure how doable it is, but it shouldn't be too complex. Licensing is another matter. I'm at a loss as to why GPU makers don't wire it up though.
I incidentally found https://hackaday.io/project/168696-cec2usb while poking around, last updated a couple years ago so probably not available for sale anymore, but open source at least.
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http://s2.symcb.com0
http://www.symauth.com/cps0(
http://www.symauth.com/rpa00
http://s1.symcb.com/pca3-g5.crl0
SymantecPKI-1-5670
Symantec Corporation1
Symantec Trust Network100.
Symantec Class 3 SHA256 Code Signing CA
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1: https://www.pulse-eight.com/p/154/intel-nuc-hdmi-cec-adapter
The listed photos are just at the wrong angle to be able to read the chip markings (grr)... but I had a bit of a further poke around, and found a listing for a discontinued internal board for HTPC (!) setups: https://www.pulse-eight.com/p/117/internal-hdmi-cec-adapter
A reasonable bit of eye-strain later I at last identified that I was staring at an AT90USB162-15AU. Here's a reference for the -16AU: https://www.mouser.com/ProductDetail/Microchip-Technology-At...
Huh. 16MHz. That answers that then.
(Now I'm a tad more idly curious why the firmware was unreadable.)
Otherwise you might try binwalk with the --disasm option (you'll need capstone installed for it to work) then it will attempt to search files for assembly for any of wide range of processors (obviously would fail if the firmware is encrypted, but I doubt a cheap product like this would bother). I'll also just briefly say that even though RCDATA is microsoft's recommended way to embed a file into an executable I've seen plenty of software that embeds files in other creative ways, so I wouldn't rule out the possibility that the firmware is somewhere else in the executable, binwalks entropy analysis mode can sometimes work firmware that is otherwise hard to locate.
While on the page I was curious if the firmware was open source. While writing this and properly articulating the bit about HDMI royalty (and also just now realizing it might need to deal with HDCP... ah) I now realize the question is moot, but I didn't think of any of what while looking at the webpage, so I wondered if it would be interesting to have a cursory poke at the firmware download.
7-Zip (also available as a commandline program as p7zip-full on debian et al) is honestly grossly understated it its capabilities. I didn't feel like remembering how to invoke binwalk so tried `7z x firmware-v7.exe` almost as a bit of a challenge and it actually worked :)
It output even more lines of metadata than I included. I removed probably 50% of output so as not to spam the subthread.Awesome.
Hmm... what if I do the same to `flash.exe`?
HMMmmmm, RCDATA you say?Extracting (`7z x ../flash.exe` from an empty subdir) produced newline-less ASCII hex output ("EF19541A19D258B099B877545DE0B65BBBC5602..."), so after a bit of `printf "$(cat 101 | sed 's/../\\x&/g')" > 101.bin` I came up with... nothing.
Binwalk has no idea what it is. Perhaps the start of the files ring bells for some humans?
For what it's worth, having realized this might be touching HDCP or for all I know might be an FPGA bitstream, I emphasize my interest is purely coming from a decidedly non-exhaustive sense of "ooh that's a cute product, I wonder what firmware it runs and how it broadly works internally" entirely made up of idle curiosity :)