first design for an hdmi to lvds adapter


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by EiNSTeiN_ » Fri Jan 13, 2012 1:58 am
hello forum,

I have a significant number of LCD panels from old laptops, so I was disappointed when I saw that the r-pi didn't have an lvds output. Given the fact that we don't (and probably won't) have access to the gpu docs or drivers source code, I have doubts on just how straightforward it will be to use the onboard DSI connector.

So I made this today, it's an hdmi to lvds adapter: http://g3nius.org/hdmi-to-lvds.tar.gz

This is an early board design, there are a couple things I haven't worked out, so it will definitely change before I have it produced. I wanted to share this sooner rather than later. It would be great if anyone with electronics knowledge could review the schematics. I made this in an afternoon so more pair of eyes won't hurt.

It works using 2 ICs, the first one is a hdmi receiver and the other one is an LVDS transmitter. between them there is 3 x 8-bit color channels, or 24 bit total. The LVDS transmitter has several modes, the one I used will be compatible with 18-bit displays aswell as [some] 24 bit displays. According to the datasheet, it will be compatible with only a minority of 24-bit capable displays but this is fine since I mostly have 18-bit LCD displays available.

The current BOM should cost in the area of 25$ for a single unit. The main IC on there is the ADV7611 which cost 15$ at digikey. It may be possible to sample the other IC from Texas Instrument and save 7$.

EiN'
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by Gert van Loo » Fri Jan 13, 2012 12:19 pm
Look at Toshiba's website. They have DSI to LVDS converters. But there is no datasheet with details unless you request them. I just posted a request for that yesterday. If I get the data sheets and if you can wait a few months we will test here at Broadcom if that works. May save you a lot of trouble and cost.
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by grmnygrmny » Fri Jan 13, 2012 2:18 pm
Gert said:


Look at Toshiba's website. They have DSI to LVDS converters. But there is no datasheet with details unless you request them. I just posted a request for that yesterday. If I get the data sheets and if you can wait a few months we will test here at Broadcom if that works. May save you a lot of trouble and cost.



I was under the impression that the DSI on the board wasn't hard connected to the GPU, i.e. no acceleration?
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by Gert van Loo » Fri Jan 13, 2012 3:46 pm
grmnygrmny said:


Gert said:


Look at Toshiba's website. They have DSI to LVDS converters. But there is no datasheet with details unless you request them. I just posted a request for that yesterday. If I get the data sheets and if you can wait a few months we will test here at Broadcom if that works. May save you a lot of trouble and cost.


I was under the impression that the DSI on the board wasn't hard connected to the GPU, i.e. no acceleration?



Where did you get that idea from? All video ports, in or out, are handled by the GPU.
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by Neon22 » Sat Jan 21, 2012 11:22 am
Interestingly here is a board that converts DVI to LVDS specifically targetting the PixelQi display. PQ3Qi-01

http://www.systemation-inc.com.....o-adapters

This is a 10.1 inch display  LVDS Single Channel. The LCD is 6 bits per color. Resolution is 1024 x 600. Also drives the backlight.

It looks like a complex design. I had hoped it would be simpler than this. I believe this card cost approx 255 USD.

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by EiNSTeiN_ » Mon Jan 23, 2012 3:07 pm
255$ is excessive ... I re-worked my first design with a less expensive IC and the bill of material would come up to around 24$ for a single unit (it goes down with volume...).
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by funny » Tue Jan 24, 2012 11:15 am
EiNSTeiN_ said:


255$ is excessive ... I re-worked my first design with a less expensive IC and the bill of material would come up to around 24$ for a single unit (it goes down with volume...).



Hi, Good work. Many people here looking for this alternative.

Many thanks.
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by lokiji » Mon Feb 13, 2012 11:28 am
guys, may I ask you, how far is this project? Does it work or not? Cos I have a spare laptop screen and would like to connect it to the raspi.
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by Thedge » Sat Feb 18, 2012 5:17 am
hi gentlemen, i couldn't follow the whole thread  due to i don't know much of the terms , any ideas where i can get more info about all of these? (i tried dsi connector in google and get  nintendo's console links only ), and about that i hear nintendo ds  screens are cheap and usually they fit in any project.

thanks in advance for any help
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by DB2k » Thu Apr 12, 2012 9:55 pm
Hi

I can barely contain myself but it looks like someone might have made what I (we?) want?

I've asked for teh data sheet

http://www.alibaba.com/product.....board.html
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by MattPurland » Sat Apr 14, 2012 12:15 pm
You might want to check this out: http://stores.ebay.co.uk/njytouch
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by Gert van Loo » Sat Apr 14, 2012 1:20 pm

i couldn't follow the whole thread  due to i don't know much of the terms ,


DSI is a standard interface not a standard connector (search for MIPI). The two 'thusfar unused' ZIF connectors on the Raspi are one for DSI (Raspi->DSI-screen) and one for CSI (Camera->Raspi).
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by zfh10 » Sun Apr 15, 2012 9:14 am
DB2k said:


Hi

I can barely contain myself but it looks like someone might have made what I (we?) want?

I've asked for teh data sheet

http://www.alibaba.com/product.....board.html



or this?

http://www.alibaba.com/product.....A_DVI.html

I'd love it if we could source a cheap small LCD and controller board
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by DB2k » Sun Apr 15, 2012 9:26 am
zfh10 said:


DB2k said:


Hi

I can barely contain myself but it looks like someone might have made what I (we?) want?

I've asked for teh data sheet

http://www.alibaba.com/product.....board.html


or this?

http://www.alibaba.com/product.....A_DVI.html

I'd love it if we could source a cheap small LCD and controller board


Right - but for me thats not too great as I wanted a USB controller for a touch screen.
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by zfh10 » Sun Apr 15, 2012 9:37 am
this is $29, has HDMI, LVDS, DVI, and VGA?

http://www.ebay.com/itm/LVDS-V.....3f15c5e244
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by burtonshaw » Thu Apr 19, 2012 4:34 pm
One of these may be suitable http://stores.ebay.com/njytouc.....4340.l2563

My add-on to this, is how difficult would it be to find and use a laptop battery to power this and the raspberry - pi?
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by john_wage » Thu Apr 19, 2012 5:04 pm
The major downer with all the ones I've found already is they are very BULKY mainly because they have features not needed!

For instance they convert analog (VGA or RCA) signals also.. the entire IC used for converting analog signals is completely useless.. dead space. Digital to digital is just a  rearrangement of the bits, it can be done with one tenth of the components / space of one of those multi-purpose converters!
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by simplyfred » Fri May 11, 2012 12:18 am
The laptop screen i've just used with an NJYtouch LCD controller connects straight to the LCD pannel by LVDS connector, touch screen to USB.

Works in the car from regulated connector and with a 12v power supply in house.
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by simplyfred » Fri May 11, 2012 12:22 am
PS DVI as well on the board and nice crisp clear display, could have had a HDMI board  but Car PC didn't need it.
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by larsanders » Fri May 11, 2012 12:30 am
simplyfred said:





That"s nice. Please do a write up later about the setup.

I am trying to find an solution which would allow me to connect to an 1080p laptop LED-backlit LCD via HDMI, but I only find LED-backlit compatible controllers that have single channel LVDS. I would be great if the thread starter has made any progress on his board, so that we could have a small and compact board for this.
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by taco24 » Wed May 30, 2012 10:00 am
Unfortunately I'm not very familiar with LVDS but it seems to be quite complex so it won't be possible for hobbyists to implement it on their own.
If someone would make an easy adapterboard to connect any LVDS-screen to a raspberry pi the whole project would get an incredible boost around the world, because the low-cost raspi-board could be used for a wide range of additional applications (embedded systems, portable consoles, steering computer for robots and machines, home automation station, and many more ...) where there are currently no open hardware alternatives.
If it is possible to make it run with bulk (low cost) LVDS-screens out-of-the-box (nintendo ds-screens, iphone-screens, etc) it would be a perfect solution because those screens can be purchased easely on ebay..

As I understand it the LCD screens cannot be powered by the raspi so an additional power supply is mandatory. Maybe the raspi could be powered by the LVDS-adapter-board though.
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by peculiar2u » Thu May 31, 2012 4:59 pm
For those of you that want to attach an LCD panel to the Raspberry Pi I have discovered that several LCD manufactures are starting to make MIPI (SDI) panels in larger sizes. Check out this link: http://www.panelook.com/modelsearch.php ... ton=Search

I've been looking for an 8" panel solution to use with the Raspbery Pi and Hydis now makes a panel with an MIPI interface. The problem is that I can't find anyone to give me a quote on one...
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by Gert van Loo » Fri Jun 01, 2012 8:07 am
peculiar2u wrote:......The problem is that I can't find anyone to give me a quote on one...


The only way to get them interested is asking for a quote for 100K up.
I have done that occasionally. The problem you have after that is they will bombard you with emails and phone calls asking when the order is likely to happen.
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by paddyg » Thu Jun 28, 2012 9:30 pm
Any progress on this? On the mouser site they price 100unit quantities at
£2.92 for SN75LVDS83BDGGR
£4.89 for TFP401APZP (Texas design for adapter:http://www.ti.com/lit/an/slla325/slla325.pdf)
pcb and assembly is cheap in China as we know.
also https://groups.google.com/forum/?hl=en-GB&fromgroups=#!forum/pi3d
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by cosardindar » Sun Jul 01, 2012 11:54 pm
Hi! There is some solution by TI. It takes the video part of the hdmi side and reverts to lvds. This is a 2 chip solution. Used chips are TFP501 http://www.ti.com/product/TFP501 and DS90C387A http://www.ti.com/product/DS90C387A. Here is an application note about this http://www.ti.com/lit/an/slla325/slla325.pdf
Is there anybody succeeding this. I will sample these parts and have a try. But the IC's pins are so small that I am afraid if I can handle such soldering technique.
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