EXP GDC HDMI-to-mPCIe wiring diagram
Here you go!
BEWARE to asses correctly the pin number on the HDMI connector, you will notice that on the pic there is 2 lines with pin number.
The upper one is for the HDMI cable connector view, the line under is for the EXP GDC HDMI connector, since when you look at and pug it it invert the pin number.
Thank you a lot nando4, i forgot to open a new thread like you asked. ^^
- Just to clarify, i mapped the cable using the continuity mode of a multi-meter, checking carefully each pin/trace on the mpci-e/HDMI connector.
- I also checked with the impedance mode, to check if i missed some connection due to internal SMD component present, but not visible to me, not visible with the continuity mode.
- I got the same result in both cases after checking carefully, you should also recheck, because i didn't opened the cable to look for inside!
- BUT, i can't say for sure this is real pinout, so take it at your own risk.
Always happy to help out! ^^
Retro-engineering the GDC v8.4d give some nice info:
- About the usb port:
- There is a 3rd jumper on the EXP GDC pcb called slim line with 2 mode, default and ultra.
- It seems the slim line switch control if the usb port is active, the pcb traces seems be routed to GND when ultra mode is ON, toward the HDMI connector when default.
- I didn't found any USB DATA +/- pins when mapping the GDC connector, either i miss them either they route on existing pins already used.
- I never tried the usb port, put the switch on ultra and never thought back about after.
- It work maybe if there is no video adapter connected to the GDC, the only possible solution i saw to possibly get the USB work.
This together let me think, if i didn't find any pin for USB DATA +/-, it is greatly probable the usb didn't work or the usb is routed on pci-e by a new unknown dark technology! I think they included in the design in the previous build, maybe, on the next design v9.0, the usb port is replaced by the 2nd HDMI connector for the pci-e lanes 3/4.
I could only assume that what make atm the EXP GDC work well with the v2.0 link, it is the fact there is no interference from the cable, especially by the usb data! The EXP GDC cable is really sensible to EM noise, wireless, smartphones, home electric furniture, etc.
- To check if the EXP GDC 8.4d shielding was good enough, i added a second layer of aluminum to shield against EM noise, connected to the HDMI ground shroud. Here some pictures how to! Obviously this was quickly done, you can improve this with more layers, also sleeve a wire inside to get a proper ground shielding, cover with normal tape to isolate the external layer.
- Take some double side tape and aluminum foil. Cut the desired length. Apply the foil on one side. Bend the edges and cut the excess.
- Get the tape stretched, turn it on the other side and stick the cable on it. You can decide how to do it better, more than one turn, etc. Time spent here: 5min.
- The job done quickly, but the result is not so bad. If you do it carefully with more turns it should end up nice and solid. But a bit less flexible!
- I did not notice further ingame fps improvement with this additional shielding. Still the room is small and not so noisy EM side. Maybe this would help in others situations.
=>Meaning anyway that the cable itself is not so bad when providing v2.0 link specs, at least the basic ones!
=> I clearly noticed a big improvement were there is a lot of EMI, i.e when my washing machine is running. I did not notice any link/screen corruption this time, was odd since i thought about it far after when i was putting the cloth to dry! OP SUCCESS! ^^
(Beware when manipulating your cable, beware the aluminum foil conduct electricity, so check it doesn't short anything on the laptop)
I know this is an old thread, but I just wanted to say thank you to Wimpzilla for creating this diagram for the community! I was having issues with loose wiring within the mPCIe part of the cable (due to lots of repeated use) and thanks to this I was able to both fix the cable and shorten it by 15cm.
Also, regarding the USB. I think I have discovered why it never worked for mPCIe despite it working for people like my friend who uses ExpressCard for his eGPU setup. As you identified, the Data lines are not wired up to the mPCIe end, but that's not the whole story. It turns out that if you have the HDMI + Ethernet style cable like I do (or fashion your own cable), those lines do in fact exist, and go all the way to the adapter PCB, where they don't connect to anything..... What is interesting here is that on the PCB, in addition to the 9 connections needed for the eGPU there are two unsoldered contacts. Thinking these could be USB, I checked the continuity and it appears they are in fact connected to the SMBus pins of the mPCIe. Maybe this was an error on the part of the designers or they added them only to realise they were unneeded (in the same way as all the unpopulated components). In any case, as I made my cable shorter I had some excess on the 5 loose wires in the cable, so checked continuity and found that the Red wire inside the bundle with Ground, 3.3V etc is D- and the White wire in the neighbouring bundle is D+, so I carefully soldered them directly to the mPCIe contacts and it works!
So if anyone else fancies the "fun" of resoldering their own cable, remember that you can add the USB communication back if you want to. Note that there is glue under the heatshrink to hold the wires in place (but doesn't do a good job as I discovered), so you'll need to apply some heat to get it off easily. Also, I used Sugru to re-seal the cable but I'm sure other techniques will work. Here are some pictures:
After Heatshrink and Glue removal
Resoldered Topside (note the SMBus pins are not soldered to despite looking like wires go to them)
I hope others will find this useful
Thanks in advance
I was Hoping someone would be able to help me make a new hdmi to m.2 nvme I see that they have the diagram for hdmi to pcie and hdmi to express card but what about Nvme m.2 to hdmi an since im using the v9.0 I would need to take both ends off of an hdmi and re-solder/wire them to the nvme m.2 slot any help please :(((