EricMiddleton
Posts: 47
Joined: Wed Jan 18, 2012 3:47 am

Re: Touch Screen LCD

Thu Jan 19, 2012 1:47 am

I will need to interface with a touch screen LCD for a project I'm going to be working on. Does this panel seem good: http://search.digikey.com/us/e.....ND/2165879 ? And if I get it, what are my options for interfacing it with the RPi? And how would I connect the touch sensor? Thanks for any help you can give me.

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tzj
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Re: Touch Screen LCD

Thu Jan 19, 2012 2:53 am

from what I"ve seen on the data sheet, it MAY work by HDMI but the LED back light requires just under 20v to run.

and there"s me thinking LEDs were low voltage, in this context.
http://www.themagpi.com <---- Checkout the MagPi
(The MagPi - Co-Founder)

EricMiddleton
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Re: Touch Screen LCD

Thu Jan 19, 2012 3:24 am

Thanks for the reply. I can manage a 20v connection, I'm just worried about connecting the LCD data signals to the board. If I were to connect using HDMI, how would I do it? I'm assuming I would need some sort of HDMI controller?

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tzj
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Re: Touch Screen LCD

Thu Jan 19, 2012 3:36 am

well I may be confusing myself with this a little bit but you could use an HDMI to dvi adapter and match the pinouts? someone will either back me up or tell me am completely wrong, but that"s how we learn
http://www.themagpi.com <---- Checkout the MagPi
(The MagPi - Co-Founder)

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tzj
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Re: Touch Screen LCD

Thu Jan 19, 2012 3:39 am

n yes you"d more than likely need an d/a controller.
http://www.themagpi.com <---- Checkout the MagPi
(The MagPi - Co-Founder)

Themroc
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Re: Touch Screen LCD

Thu Jan 19, 2012 4:09 am

Eric Middleton said:


Does this panel seem good: http://search.digikey.com/us/e.....ND/2165879 ? And if I get it, what are my options for interfacing it with the RPi? And how would I connect the touch sensor?


This one needs sync signals + 3*8 bit digital RGB, which is not available on the RasPI. You could get that out of some converter chip from HDMI or (probably easier) DSI. The Toshiba TC358762XBG might do the trick, but don't ask me where to get it. The touch sensor also needs a chip, I'd guess it has to contain at least 2 ADCs.

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rurwin
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Re: Touch Screen LCD

Thu Jan 19, 2012 8:25 am

I'm sure it would make a great project, but by the time you had built everything that needed building, would it be any cheaper than this?

(There's loads of companies selling those from China, all using the same text. That one is cheaper than the rest. Caveat emptor.)

rabc
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Re: Touch Screen LCD

Thu Jan 19, 2012 12:28 pm

What about buying generic screens from China? Like this screen.

EricMiddleton
Posts: 47
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Re: Touch Screen LCD

Thu Jan 19, 2012 10:34 pm

The end goal is to have a small touch screen PDA-like device. So obviously cost and size are the main goals here. I am planning on making about 4-6 of them to use on an experiment involving technology in schools, so cost is really key here.

Felix
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Re: Touch Screen LCD

Thu Jan 19, 2012 11:22 pm

Ok i got a 7 inch screen (touchscreen)

for under 100$ if someone is interested i'll give the link for it.

[have to search for it]

EricMiddleton
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Re: Touch Screen LCD

Fri Jan 20, 2012 8:20 pm

7 inches is way too big for this. I'm trying to get a screen that is about as big as the raspberry pi board so that it all fits nicely. I want it to feel the same as a smart phone or any other PDA, so probably a 3.5-4.5 inch max. Also, how do professionally developed PDAs and smartphones connect to screens? If they were to use the same SoC, would they use DSI or something different?

igu
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Re: Touch Screen LCD

Fri Jan 20, 2012 8:28 pm

A screen as big as the raspi?

Are you sure?

EricMiddleton
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Re: Touch Screen LCD

Fri Jan 20, 2012 9:02 pm

That would be a 4in. diagonal screen (3.98in to be exact), which fits perfectly with the purpose of the device.

EricMiddleton
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Re: Touch Screen LCD

Fri Jan 20, 2012 10:18 pm

How about this screen: http://www.newark.com/kentec-e.....20Displays ? The size is perfect, it has the touch panel and it also has a controller built in. Would I just use the GPIOs to interface with the controller?

grumble53
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Re: Touch Screen LCD

Fri Jan 20, 2012 11:15 pm

Let us know how you get on Eric. I have limited knowledge and I would appreciate hearing about your experience using such a screen.

Ian

Neon22
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Re: Touch Screen LCD

Fri Jan 20, 2012 11:47 pm


kenk
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Re: Touch Screen LCD

Sat Jan 21, 2012 12:35 am

I too am looking for a touch screen for a project, although my size requirements aren't as small as yours. I found this one which may be interesting to use, it uses USB only, so you will have to write a driver for it, but it is powered by USB as well. A powered hub might do the trick.

7 inch touch screen monitor

http://www.amazon.com/Lilliput.....B003L9FVJM

Its a bit pricey, but you may be able to find it cheaper somewhere.

EricMiddleton
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Re: Touch Screen LCD

Sat Jan 21, 2012 1:18 am

kenk said:


I too am looking for a touch screen for a project, although my size requirements aren't as small as yours. I found this one which may be interesting to use, it uses USB only, so you will have to write a driver for it, but it is powered by USB as well. A powered hub might do the trick.

7 inch touch screen monitor

http://www.amazon.com/Lilliput.....B003L9FVJM

Its a bit pricey, but you may be able to find it cheaper somewhere.


Wouldn't it be tricky to get hardware acceleration if you use a USB screen?

EricMiddleton
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Re: Touch Screen LCD

Sat Jan 21, 2012 2:23 am

OK, so here is what I have learned so far. Most LCD panels use an FPD-link (also know as an LVDS link) to interface with controllers. The Raspberry Pi has a Display Serial Interface (DSI) connector built in which is not directly compatible with the FPD link, so I would need some sort of adapter that would accept the DSI data and then transmit it to the panel using the FPD link. The only problem is that I can't seem to find a good way to do that, especially not in the form factor required for a PDA.

Themroc
Posts: 44
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Re: Touch Screen LCD

Sat Jan 21, 2012 2:34 am

Eric Middleton said:


OK, so here is what I have learned so far. Most LCD panels use an FPD-link (also know as an LVDS link) to interface with controllers. The Raspberry Pi has a Display Serial Interface (DSI) connector built in which is not directly compatible with the FPD link, so I would need some sort of adapter that would accept the DSI data and then transmit it to the panel using the FPD link. The only problem is that I can't seem to find a good way to do that, especially not in the form factor required for a PDA.


Lookie here:

"

Package
- TC358765: P-TFBGA 64-pin, 6mm x 6mm,
1.2mm height, 0.65mm ball pitch
- TC358764: P-TFBGA 49-pin, 5mm x 5mm,
1.2mm height, 0.65mm ball pitch
"

http://www.toshiba-components......65XBGA.pdf

EricMiddleton
Posts: 47
Joined: Wed Jan 18, 2012 3:47 am

Re: Touch Screen LCD

Sat Jan 21, 2012 3:20 am

Themroc said:


Eric Middleton said:


OK, so here is what I have learned so far. Most LCD panels use an FPD-link (also know as an LVDS link) to interface with controllers. The Raspberry Pi has a Display Serial Interface (DSI) connector built in which is not directly compatible with the FPD link, so I would need some sort of adapter that would accept the DSI data and then transmit it to the panel using the FPD link. The only problem is that I can't seem to find a good way to do that, especially not in the form factor required for a PDA.


Lookie here:

"

Package
- TC358765: P-TFBGA 64-pin, 6mm x 6mm,
1.2mm height, 0.65mm ball pitch
- TC358764: P-TFBGA 49-pin, 5mm x 5mm,
1.2mm height, 0.65mm ball pitch
"

http://www.toshiba-components......65XBGA.pdf


I did see that one but there are two issues with it. First of all, I don't know where I can buy one, and even if I did get one, I don't have the equipment to solder one. If you know where I can get a soldered one, like a breakout board, that would be perfect.

specsdude
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Location: In a small English village, far from the eyes of Mordor

Re: Touch Screen LCD

Sat Jan 21, 2012 2:23 pm

Some peopel mentioned getting component LCD screens from China-

After some research, I found this:

http://hk-rmt.en.made-in-china.....V-GPS.html

and I contacted manufacturers for a price quote:

For 50 pcs of A035QN02 V9, unit price is US$12.8 ( Ex-works, no tax).
We have 5K stock and you can pay us by Paypal / Western Union / TT to our company account.
 
Best regards,
 
Richard Yang 
--------------------------------------------------------------------
HONGKONG RMT ELECTRONICS CO., LTD.
I think this is the cheapest price mentioned so far, but IMO the real difficulty would be connecting it- would it need software or a d/a converter... stuff like that?
BTW I'm new here, I live in Hampshire, UK. Anyone else near me here?
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tommedema
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Re: Touch Screen LCD

Sat Jan 21, 2012 2:33 pm

Dave Seeber said:


Some peopel mentioned getting component LCD screens from China-

...


How do you connect such LCD screen to a raspberry? Don't you need to have HDMI/VGA/USB output?

Themroc
Posts: 44
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Re: Touch Screen LCD

Sat Jan 21, 2012 3:09 pm

Eric Middleton said:


First of all, I don't know where I can buy one, and even if I did get one, I don't have the equipment to solder one. If you know where I can get a soldered one, like a breakout board, that would be perfect.


It looks like you can't buy them, instead you'd have to ask these friendly folks for prices at 100.000 pcs,, "some samples" and the datasheets to be sent to


Mobile Future Inc.

Department D13

Eric Middleton

[Your Home Address]


Then buy this and that, read a bit here and there...

BTW here is the cheapest 3.5" touchscreen i found:

http://www.ebay.com/itm/iPhone.....3f0c6b598b

+

http://www.ebay.com/itm/New-Re.....3f0894dba9

Cheers!

EricMiddleton
Posts: 47
Joined: Wed Jan 18, 2012 3:47 am

Re: Touch Screen LCD

Sun Jan 22, 2012 4:03 am

Thanks for all the help; I'll call them on Monday. Quick question about the digitizer though. Can you point me in the direction of some information about it's interface? I know how the four-pin resistive panels work, but the iPhone digitizer uses projected capacitance, which I am not familiar with.

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