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 Guide - Vitrolight / Hydis LVDS connection via HDMI... 
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Sharp Eyed Eagle!

Joined: Wed Jan 13, 2010 7:12 am
Posts: 436
Location: UK
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OK, I've been meaning to do this guide for a while, but I haven't had much time recently.
I originally tried to keep this post short, but it hasn't worked so far. :)

The story up to now is that the first HDMI + USB adapters I made for Zach (zacherynuk) are working OK...
http://www.wastedspace.co.uk/cms/2012/0 ... irst-rift/

Although, there were some very slight Green "sparklies" on the panel image...
As most of you know, this is caused by the LVDS cable at the panel end not having twists in the data pairs, and because it's not properly shielded.
The HDMI cable itself appears to work great!

So, on Zach's second cable, I've put some light twists in the LVDS data pairs, then used thin foil tape on each pair to shield them from noise.

It's taken me a while to get the second cable sorted 'cos I wanted to find some HDMI connectors which were easier to solder to (the first cable used HDMI sockets cut from a cheap HDMI switch box).

(I also messed up the pinout on the second cable 'cos I didn't label the LVDS wires like I did on the first one :oops: - I'd already sent the panel and first cable back to Zach, so it was difficult to see which way around the panel plug went in :roll: ).

Anyway, so I found some of those nice HDMI twisty things and thought I'd make a guide while I'm finishing this cable.
The twisty things break apart easily and give you two little breakout boards on the HDMI sockets...
http://www.ebay.co.uk/itm/290649898092

I then unwrapped the LVDS cable and found the correct pinout order (with the help of the Hydis datasheet).

I tried to give some thought to how the power and control signals should be connected, just for the rare chance that somebody might (stupidly / accidentally) plug the LCD or controller side into a "normal" HDMI socket...

Here's what I came up with...

Normal HDMI Type A socket / plug pinout...

Pin 1. TMDS Data2+
Pin 2. TMDS Data2 Shield
Pin 3. TMDS Data2–
Pin 4. TMDS Data1+
Pin 5. TMDS Data1 Shield
Pin 6. TMDS Data1–
Pin 7. TMDS Data0+
Pin 8. TMDS Data0 Shield
Pin 9. TMDS Data0–
Pin 10. TMDS Clock+
Pin 11. TMDS Clock Shield
Pin 12. TMDS Clock–
Pin 13. CEC
Pin 14. HEC Data- (Optional, HDMI 1.4+ with Ether)
Pin 15. SCL
Pin 16. SDA
Pin 17. Ground
Pin 18. +5V
Pin 19. Hot Plug Detect

The panel LVDS data pairs should of course match the HDMI TMDS pairs (Data 2+/-, 1+/-, 0+/-, C+/-).
(All shield grounds need to be connected to Ground!)

Then, this is how I've connected the control / USB / power wires...

Pin 13. Backlight ON/OFF + PWM.
Pin 14. USB +5V (Red)
Pin 15. USB Data- (White)
Pin 16. USB Data+ (Green)
Pin 17. GND / (USB Black)
Pin 18. +5V (Backlight Supply)
Pin 19. +3V3 (Panel Supply)

Ofc, the LVDS data pairs should connect like the normal HDMI TMDS pairs do. There are just the two wires per data pair on the Hydis panel.
(no separate shield wires on the original cable, hence the sparklies!).

I then used pin 18 for the +5V backlight supply (since it's normally for +5V anyway).

The 3V3 panel supply went on pin 19 because the hot-plug detect pin in HDMI usually just has a pull-up resistor to +5V, so very little current should flow if the panel was accidentally plugged in to HDMI.

PWM + Backlight ON/OFF is usually on the White wire which plugs directly into the 6-pin connector on the controller.
I connected this via HDMI pin 13 (normally CEC, Consumer Electronics Control).

Note: The PWM and Backlight ON/OFF control signals are normally connected together inside the LVDS cable wrappings.
So, it doesn't look like these panels are using PWM for varying the backlight brightness, it's either fully ON or fully OFF.

The USB data pair (Green and White in most USB cables) should go through the DDC pins because it's likely that these pins are separately shielded inside the HDMI cable (if it's a decent cable).

USB +5V power goes through HDMI pin 14. This is usually for "Ethernet via HDMI", so you'll probably need to use a newer HDMI 1.4 cable for this pin to be connected.

(I suppose it still might do some damage if connected to a normal HDMI socket, but I tried to choose the pins in a way that minimizes the risk.)

Also important is that all the "shield" and Ground pins are connected together. On the HDMI sockets which I cut from the HDMI switch, the PCB already joins all the Grounds together, which actually made things easier.

On the HDMI twisty things, you'll need to join all the "shield" and Ground pins together manually (with short bits of wire etc.)
You can see in the photos where I've started to join the Ground pins to the metal shield / housing on the HDMI sockets.

For the controller end, I originally used a short piece of 34-pin 2mm pitch IDC connector which I had laying around.
This isn't ideal, as they're quite expensive to buy for what they are (in the UK at least). The plug was slightly longer than the controller's socket, so it overhangs the left side. I also had to remove the shroud around the white "keypad" connector to get it to fit.

For the second cable, I've re-used the original plug. It was a pain to remove the pins and solder directly to them, but it looks a lot better.

Right, so here are the important bits first... (thanks to @rfurlan for posting the datasheets)...

Watch out for the controller end plug pin ordering...
Pin 1 is closest to the white "keypad" connector, and is usually marked with a white Tipex spot on the plug (not necessarily on yours though).
Pin 2 is then directly opposite pin 1 (nearer to the PCB's edge). So, the panel "power" pins are on...

1. VSEL 3V3
2. VSEL 3V3
Then the gap of two pins is 3+4. Then...
5. GND
6. GND
And so on.

btw, it looks like the LVDS pinout for the smaller controller and the 7-in-1 are the same.

CONTROLLER END! Note: Only pins 1 to 16 are used on the 1280x800 Hydis panel...
Image

PANEL END!
Image

My crappy diagram of the signals + HDMI Sockets...
Image

Panel end plug + wires labelled...
Image

EDIT: The above picture should say 19 TO 23! These are all "nc" (no-connection) and cut short inside the original LVDS cable.
You need to ensure that the ends of these cut wires won't short out between each other, or to the foil.

There are actually some spare Ground wires which aren't normally used. You could in theory use these to ground the foils (soldering might be tricky though).

Plug + foils closeup...
http://i45.tinypic.com/2tml2.jpg

Plug + foils wide view...
http://i46.tinypic.com/rbxf9t.jpg

Controller end adapter + USB...
http://i49.tinypic.com/6gejqe.jpg

Panel end adapter closeup...
http://i45.tinypic.com/29z1ws5.jpg

FIRST cable, Zach's controller...
http://i46.tinypic.com/140gsd2.jpg

FIRST cable, Zach's panel working...
http://i46.tinypic.com/2rr0213.jpg

phew! :shock:


Last edited by OzOnE2k10 on Fri Oct 05, 2012 5:50 am, edited 4 times in total.



Thu Oct 04, 2012 11:19 am
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Binocular Vision CONFIRMED!
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Joined: Wed Aug 15, 2012 1:38 pm
Posts: 322
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Great job getting that working! I would have loved to make a guide for you guys, but Palmer told me I couldn't yet. :P It's a bit different from the way I do it, but looks like it works for you!


Thu Oct 04, 2012 1:16 pm
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Sharp Eyed Eagle!

Joined: Wed Jan 13, 2010 7:12 am
Posts: 436
Location: UK
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I know, I read somewhere that you were sworn to secrecy. lol

This isn't really exposing any secrets I suppose, just need the datasheets and a bit of soldering skill.

I've just seen WickedAndy's great post though. Doing a PCB layout would have been ideal, but it's difficult to find cheap PCB makers here in the UK....
viewtopic.php?f=140&t=15247&start=510#p83258

So, my "guide" is probably only good for reference - I would definitely recommend using some of those breakout boards instead.
Maybe Andy or somebody could do a group buy or something?

I did think about using HDMI + USB "chassis mount" cables, but they're also quite expensive when priced up.

OzOnE.


Thu Oct 04, 2012 1:25 pm
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Joined: Wed Aug 15, 2012 1:38 pm
Posts: 322
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A breakout board would be awesome. Unfortunately, I have to crank these things out so quickly that I don't have time to wait for boards. I may have to design my own eventually, though, and etch them myself. Hopefully by then we'll actually have dev kits, though!


Thu Oct 04, 2012 1:35 pm
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Sharp Eyed Eagle!

Joined: Wed Jan 13, 2010 7:12 am
Posts: 436
Location: UK
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Andy said he'll post the gerber files soon, so anyone could then send them off to a board house.

There are some cheaper places around than what I usually use (especially in the US).
In bulk, they should work out very cheap, and that's including the HDMI sockets / headers etc.

If anyone does decide to make their own cable though - make sure you label the wires on the LVDS cable! :P


Thu Oct 04, 2012 1:51 pm
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One Eyed Hopeful

Joined: Sat Sep 08, 2012 2:06 am
Posts: 47
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Amazing guide OzOnE2k10, thank you for the awesome instructions! I'm still hoping you'll sell these at some point. :)


Thu Oct 04, 2012 2:28 pm
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Golden Eyed Wiseman! (or woman!)

Joined: Fri Jul 08, 2011 11:47 pm
Posts: 1498
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Wow, great info OzOnE2k10!


Thu Oct 04, 2012 10:05 pm
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Binocular Vision CONFIRMED!
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Joined: Sun Oct 03, 2010 2:56 pm
Posts: 295
Location: England
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And I can confirm the first cable works a charm :)

Speckles are really not a problem, when strapped to your head they seem to dispear, so unsure where the dodgy LVDS end bit is picking up the EMI.

Cracking job, and a cracking guide for those with a steady hand :)

_________________
My HMD Blog: http://www.wastedspace.co.uk/cms/category/projects/vintage-head-mounted-display-upgrade/


Fri Oct 05, 2012 4:42 am
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Sharp Eyed Eagle!

Joined: Wed Jan 13, 2010 7:12 am
Posts: 436
Location: UK
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Thanks, guys.

@Zach - That's good to know...

Yep, the sparklies were quite subtle, and only visible on certain scenes (usually on high-contrast edges).
So, I wanted to make this second cable better. I've just finished it, and it wasn't too bad at all to wrap the foils...

btw, the foil tape I used worked quite well. The cable is still fairly flexible, and that won't matter too much once it's in the HMD anyway...
http://www.ebay.co.uk/itm/Self-Adhesive ... 0838144149

(I've linked to the photos here to save space on the post)...

Foils + panel end adapter done...
http://i46.tinypic.com/9uy877.jpg

Foils grounded...
http://i50.tinypic.com/fdeu5x.jpg

Foils wrapped + panel end adapter closeup...
http://i47.tinypic.com/v61xc6.jpg

Foils wrapped + TFT connector closeup...
http://i45.tinypic.com/fd9e0j.jpg


You can see I've sandwiched the LVDS data pairs between two strips of foil tape.
I've also used the spare Ground wires from the TFT end to Ground the foils themselves. I then carefully re-wrapped the whole thing.

I don't think it's at all necessary to use foil on anything other than the data pairs.
In fact, it would probably be good enough just to lightly twist the data pairs together before soldering to the HDMI adapter.

To save the hassle of unwrapping the cable at all, a single layer of shielding around the whole cable might work too.
It's more ideal to shield each data pair separately (like I've done) to avoid crosstalk, but I might be going a bit overboard tbh.

btw, it's important to take notice of the polarity of the data pairs. Each pair has a "plus" and "minus" wire, and it won't work if those get swapped!

On the first cable, I also used epoxy on the HDMI adapters to cover the solder points and hold the wires in place.
Again, it's not really mandatory either, but will obviously make the cable stronger.
If you do use epoxy, it would be better to use some flexible silicon stuff instead (so the wires can move a bit without putting strain on them).

Of course, you should thoroughly test your cable and the USB pass-through connection before using epoxy etc.
Also make sure the panel / backlight / USB power connections are definitely correct and not shorted to other wires or to each-other.

The Hydis panel itself runs on 3.3V (labelled "VSEL" on the controller pinout and "VDD" on the panel pinout).

The backlight is usually +5V and is powered from the controller via the small plug with the red wire.
(the panel has a step-up converter for the LED backlight).

btw, I've already got the 5x lenses from the US and will be buying a panel + controller very soon.
I'm not so great with the physical construction part, so no doubt I'll be badgering people on here for info. ;)

Unfortunately, UK customs decided to charge me £11 extra just for the privilege of buying the £25 lenses. :(
Oh well, that's the chance you take. It was only USPS as well, so customs just like to be awkward I guess.


Fri Oct 05, 2012 5:47 am
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Joined: Wed Aug 15, 2012 1:38 pm
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Well no wonder you guys are getting sparkles! Those wires are really long. I keep them 1-1.5" on each side, and I don't need any foil for a perfect picture. Why make them so long?


Fri Oct 05, 2012 5:54 am
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Sharp Eyed Eagle!

Joined: Wed Jan 13, 2010 7:12 am
Posts: 436
Location: UK
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It's a good point, as personally I would make it just long enough for the HDMI socket to reach the outside edge of the HMD case.

I only kept it longer to give people the choice in where to place the socket on their HMD.
I see what you mean though, it wouldn't take much to avoid the sparklies.

I think it's just the LVDS end which is most susceptible.
Like you say, keeping the cable shorter should do the trick (and maybe putting a few light twists in the data pairs?).


Fri Oct 05, 2012 6:41 am
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Two Eyed Hopeful
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Joined: Mon Oct 31, 2011 4:04 pm
Posts: 64
Location: waltham abbey essex uk
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OzOnE2k10 wrote:
OK, I've been meaning to do this guide for a while, but I haven't had much time recently.
I originally tried to keep this post short, but it hasn't worked so far. :)

The story up to now is that the first HDMI + USB adapters I made for Zach (zacherynuk) are working OK...
http://www.wastedspace.co.uk/cms/2012/0 ... irst-rift/

Although, there were some very slight Green "sparklies" on the panel image...
As most of you know, this is caused by the LVDS cable at the panel end not having twists in the data pairs, and because it's not properly shielded.
The HDMI cable itself appears to work great!

So, on Zach's second cable, I've put some light twists in the LVDS data pairs, then used thin foil tape on each pair to shield them from noise.

It's taken me a while to get the second cable sorted 'cos I wanted to find some HDMI connectors which were easier to solder to (the first cable used HDMI sockets cut from a cheap HDMI switch box).

(I also messed up the pinout on the second cable 'cos I didn't label the LVDS wires like I did on the first one :oops: - I'd already sent the panel and first cable back to Zach, so it was difficult to see which way around the panel plug went in :roll: ).

Anyway, so I found some of those nice HDMI twisty things and thought I'd make a guide while I'm finishing this cable.
The twisty things break apart easily and give you two little breakout boards on the HDMI sockets...
http://www.ebay.co.uk/itm/290649898092

I then unwrapped the LVDS cable and found the correct pinout order (with the help of the Hydis datasheet).

I tried to give some thought to how the power and control signals should be connected, just for the rare chance that somebody might (stupidly / accidentally) plug the LCD or controller side into a "normal" HDMI socket...

Here's what I came up with...

Normal HDMI Type A socket / plug pinout...

Pin 1. TMDS Data2+
Pin 2. TMDS Data2 Shield
Pin 3. TMDS Data2–
Pin 4. TMDS Data1+
Pin 5. TMDS Data1 Shield
Pin 6. TMDS Data1–
Pin 7. TMDS Data0+
Pin 8. TMDS Data0 Shield
Pin 9. TMDS Data0–
Pin 10. TMDS Clock+
Pin 11. TMDS Clock Shield
Pin 12. TMDS Clock–
Pin 13. CEC
Pin 14. HEC Data- (Optional, HDMI 1.4+ with Ether)
Pin 15. SCL
Pin 16. SDA
Pin 17. Ground
Pin 18. +5V
Pin 19. Hot Plug Detect

The panel LVDS data pairs should of course match the HDMI TMDS pairs (Data 2+/-, 1+/-, 0+/-, C+/-).
(All shield grounds need to be connected to Ground!)

Then, this is how I've connected the control / USB / power wires...

Pin 13. Backlight ON/OFF + PWM.
Pin 14. USB +5V (Red)
Pin 15. USB Data- (White)
Pin 16. USB Data+ (Green)
Pin 17. GND / (USB Black)
Pin 18. +5V (Backlight Supply)
Pin 19. +3V3 (Panel Supply)

Ofc, the LVDS data pairs should connect like the normal HDMI TMDS pairs do. There are just the two wires per data pair on the Hydis panel.
(no separate shield wires on the original cable, hence the sparklies!).

I then used pin 18 for the +5V backlight supply (since it's normally for +5V anyway).

The 3V3 panel supply went on pin 19 because the hot-plug detect pin in HDMI usually just has a pull-up resistor to +5V, so very little current should flow if the panel was accidentally plugged in to HDMI.

PWM + Backlight ON/OFF is usually on the White wire which plugs directly into the 6-pin connector on the controller.
I connected this via HDMI pin 13 (normally CEC, Consumer Electronics Control).

Note: The PWM and Backlight ON/OFF control signals are normally connected together inside the LVDS cable wrappings.
So, it doesn't look like these panels are using PWM for varying the backlight brightness, it's either fully ON or fully OFF.

The USB data pair (Green and White in most USB cables) should go through the DDC pins because it's likely that these pins are separately shielded inside the HDMI cable (if it's a decent cable).

USB +5V power goes through HDMI pin 14. This is usually for "Ethernet via HDMI", so you'll probably need to use a newer HDMI 1.4 cable for this pin to be connected.

(I suppose it still might do some damage if connected to a normal HDMI socket, but I tried to choose the pins in a way that minimizes the risk.)

Also important is that all the "shield" and Ground pins are connected together. On the HDMI sockets which I cut from the HDMI switch, the PCB already joins all the Grounds together, which actually made things easier.

On the HDMI twisty things, you'll need to join all the "shield" and Ground pins together manually (with short bits of wire etc.)
You can see in the photos where I've started to join the Ground pins to the metal shield / housing on the HDMI sockets.

For the controller end, I originally used a short piece of 34-pin 2mm pitch IDC connector which I had laying around.
This isn't ideal, as they're quite expensive to buy for what they are (in the UK at least). The plug was slightly longer than the controller's socket, so it overhangs the left side. I also had to remove the shroud around the white "keypad" connector to get it to fit.

For the second cable, I've re-used the original plug. It was a pain to remove the pins and solder directly to them, but it looks a lot better.

Right, so here are the important bits first... (thanks to @rfurlan for posting the datasheets)...

Watch out for the controller end plug pin ordering...
Pin 1 is closest to the white "keypad" connector, and is usually marked with a white Tipex spot on the plug (not necessarily on yours though).
Pin 2 is then directly opposite pin 1 (nearer to the PCB's edge). So, the panel "power" pins are on...

1. VSEL 3V3
2. VSEL 3V3
Then the gap of two pins is 3+4. Then...
5. GND
6. GND
And so on.

btw, it looks like the LVDS pinout for the smaller controller and the 7-in-1 are the same.

CONTROLLER END! Note: Only pins 1 to 16 are used on the 1280x800 Hydis panel...
Image

PANEL END!
Image

My crappy diagram of the signals + HDMI Sockets...
Image

Panel end plug + wires labelled...
Image

EDIT: The above picture should say 19 TO 23! These are all "nc" (no-connection) and cut short inside the original LVDS cable.
You need to ensure that the ends of these cut wires won't short out between each other, or to the foil.

There are actually some spare Ground wires which aren't normally used. You could in theory use these to ground the foils (soldering might be tricky though).

Plug + foils closeup...
http://i45.tinypic.com/2tml2.jpg

Plug + foils wide view...
http://i46.tinypic.com/rbxf9t.jpg

Controller end adapter + USB...
http://i49.tinypic.com/6gejqe.jpg

Panel end adapter closeup...
http://i45.tinypic.com/29z1ws5.jpg

FIRST cable, Zach's controller...
http://i46.tinypic.com/140gsd2.jpg

FIRST cable, Zach's panel working...
http://i46.tinypic.com/2rr0213.jpg

phew! :shock:


Sat Mar 02, 2013 6:12 am
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