8.9 touch screen solution


18 posts
by godFather89 » Mon May 21, 2012 1:50 pm
I've decided to add a touch screen to my raspberry pi and wanted to share the progress.

As an LCD panel, I decided to use a 8.9" WSVGA (1024x600), 18 bit (260 Kcolors) LCD panel (A089SW01). This panel has the advantage that it has built in backlight controller and has a pretty good resolution at a decent size. This kind of LCD panel can be found on ebay pretty cheap (but not as cheap as RPi). I ordered one at a total cost of 205 RON.
There are 8.9" rezistive touch panel kit's on ebay with a total cost of 150 RON. Haven't ordered yet, I'm waiting to finish the LCD.
The LCD will be driven from the HDMI output, using the TFP403 and SN75LVDS83 chips. The LCD panel also has EDID I2C interface. I have no problem with designing and making my own PCB (already made lots of PCBs with 0.5mm pin space). The total cost for the controller would be at about 50 RON.

So the total cost for this RPi addon would be about 400 RON (~125 $). Pretty expensive but I think it's all worth it.

For now I ordered the LCD panel. After the panel arrives, I'll start working on the controller and the touch panel will be the last piece.

After all this is done, I am thinking of making the whole thing portable (much like a tablet). From what I've read, the RPi draws about 2.4W from the 5V power source. I noticed the regulators on the board are linear regulators which are not very efficient. I was thinking of adding a battery pack and a little step down PSU that gives all the required voltages 5V and 3.3V at maximum efficiency. I would estimate that the whole thing will draw at maximum 5W (including the PSU inefficiency), which means that from a 44Wh notebook battery pack it would stay awake at full processing power for about 9 hours.

Any opinions?
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by godFather89 » Mon May 21, 2012 1:52 pm
I forgot to add that the LCD panel will arrive in about 3-4 weeks so I have a lot of time of thinking and designing.
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by jack3d » Mon May 21, 2012 2:08 pm
any links to the display? price?
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by godFather89 » Mon May 21, 2012 2:59 pm
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by godFather89 » Tue May 22, 2012 8:53 am
I noticed there are lots of 8.9" capacitive touch digitizers as replacements for Samsung P7300. Like this one from ebay.
I'm wondering if there can be found any documentation for this digitizers since a capacitive (multi)touch panel would be more fun than a rezistive one.
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by Swiftek » Fri May 25, 2012 12:46 am
That sounds like an exciting project, and I find myself wishing I had your PCB skills. I'm a PC tech from way back, but I don't even own a multi-touch device yet, so I don't have a clue where to start with that.

Are the touch panels that you refer to separate from the display? Is that a typical design for modern gadgetry like phones and tabs?

I'm interested in building something similar and I'd love to hear how the vid controller turns out. Please update us when you can.
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by godFather89 » Fri May 25, 2012 5:37 am
Swiftek wrote:That sounds like an exciting project, and I find myself wishing I had your PCB skills. I'm a PC tech from way back, but I don't even own a multi-touch device yet, so I don't have a clue where to start with that.

Me neither. Well I actually have a Desire, but the multitouch part is not that good...

Swiftek wrote:Are the touch panels that you refer to separate from the display? Is that a typical design for modern gadgetry like phones and tabs?

In most designs they are separate so that if you break the touch panel, you don't replace the screen too.

Swiftek wrote:I'm interested in building something similar and I'd love to hear how the vid controller turns out. Please update us when you can.

I'm designing it. The LCD panel should arrive next week but I'm not sure I can work on it in the next weeks (since I'll have a big exam).
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by Swiftek » Fri May 25, 2012 2:38 pm
Thanks for all the info. I look forward to hearing what you learn and seeing what you come up with.

Are you designing and building the controller yourself because there isn't anything off the shelf that will do what you want?
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by godFather89 » Sat May 26, 2012 11:05 am
I hope this project will be finished somewhere in the middle of June (just the screen, no touch panel).
I'm designing it myself because the commercial ones are pretty big (since they have some functionality I don't need) and I hope mine will be a bit smaller and the power consumption will also be smaller. And, of course, I'm designing it to learn something new...
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by Stephan123 » Mon May 28, 2012 9:23 am
Hello !

Can you post a picture of the finished project?

Yours sincerely,

Stephan
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by godFather89 » Mon May 28, 2012 11:13 am
As soon as I get it working... If I get it working :D
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by Stalthy » Mon May 28, 2012 12:59 pm
Dear forum users. On the norwegian forum Diskusjon.no there was a user which have posted a worklog.

The text is in Norwegian, i could probaly translate some parts, but not too much. This shows that he have gotten an screen and has probaly answears to many of your questions, if you have any pherhaps i could translate them and post them into his worklog? ;)

Link: http://www.diskusjon.no/index.php?showtopic=1431272
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by Bluemerlin » Mon May 28, 2012 1:46 pm
Stalthy wrote:Dear forum users. On the norwegian forum Diskusjon.no there was a user which have posted a worklog.

The text is in Norwegian, i could probaly translate some parts, but not too much. This shows that he have gotten an screen and has probaly answears to many of your questions, if you have any pherhaps i could translate them and post them into his worklog? ;)

Link: http://www.diskusjon.no/index.php?showtopic=1431272



Google has done it's best guess at translation. I would have thought that screen with work out of the box. The 7" liliput takes hdmi input and outputs touchscreen as a standard USB HID device.

Very little to configure, but not cheap.
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by slippern » Mon May 28, 2012 7:47 pm
Im going to order the Lilliput screen for my car setup.
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by warlock666 » Thu May 31, 2012 5:48 pm
Is the liliput touchscreen multitouch ?
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by godFather89 » Thu Jun 07, 2012 7:35 pm
Here I am again with some feedback. I did the little board but all I get are some vertical stripes on the screen (some 15" XGA lcd panel). The problem is that it's kind of impossible to meat the PCB requirements for a diy board.

But, I found this board on ebay and it seems just perfect (12-15 quid). With some tweaking (if not directly) should work with the raspberry. The problem is that the seller doesn't ship to Romania. If anyone from UK could buy one and sell it afterward to me, it would be great.

Thanks!
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by godFather89 » Fri Jun 08, 2012 12:59 pm
Well, I guess I'll go with a lapdock. Seems much cheaper since you get a screen, keyboard+trackpad, usb hub and battery pack + charger all for about 120$ (even less if you can get a good deal).
The thing is I ordered the LCD screen, now I have to find someone to buy it (idiot me) :( .
Maybe I'll even mod it so that the keyboard+trackpad can be deattached from the rest of the "tablet" and give the screen a touch panel.
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by rfincher1 » Wed Jun 27, 2012 6:41 pm
Here's a touch screen monitor with 1600x1200 and 1080p that runs on 12 volts for $148 USD, free shipping. USB interface for the touch screen:

http://www.aliexpress.com/product-fm/58 ... alers.html

Rick
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