Would this $3 touchscreen work?


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by oso2k » Sat Jan 05, 2013 2:19 am
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by aTao » Sat Jan 05, 2013 3:04 am
Sure, no problem, if you can work out how to read the touch screen X and Y resistance and how to connect to the flexible circuit cables that have contact pads 0.3*0.5mm
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by oso2k » Sat Jan 05, 2013 4:27 am
I'm an electronics newb. How would recommend connecting this to the Pi's composite or HDMI jacks? Is some intermediate board necessary? Is it necessary to connect via GPIO?

I found the datasheet (http://beyondinfinite.com/lcd/Library/Sharp/LQ038J7DH52.pdf/) on it just now.
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by aTao » Sat Jan 05, 2013 10:12 am
oso2k wrote:I'm an electronics newb. How would recommend connecting this to the Pi's composite or HDMI jacks? Is some intermediate board necessary? Is it necessary to connect via GPIO?

I found the datasheet (http://beyondinfinite.com/lcd/Library/Sharp/LQ038J7DH52.pdf/) on it just now.


If you call yourself an electronics newb then this is not a good project. Making a connection with the display is a huge challenge for anyone that does not have the correct socket to plug it into. Its a shame since there are many mobile device displays like this one that are cheap.

If you could make he electrical connection then the data sheet has all the signal information, you would have to program the GPIO, HDMI could be used but would need a lot of interface circuitry (again not really suitable for a "newb") At first glance it looks like the display requires that you set up 6 bits of Red, Green and Blue data then pulse a clock signal. Also there is a sync signal to indicate start of frame and start of line. So, using GPIO, you would need extra GPIO pins or equivalent (like output and latch each of R,G,B)

As a rule, if there is any part of the data sheet that you dont understand then you are going to find it very difficult to design a circuit from scratch.


But if you really want to try, then go on, give it a go, some people find it better to learn that way. You will almost certainly need a microscope to solder a connection to it.
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by oso2k » Sat Jan 05, 2013 11:02 am
I think I'll attempt the HDMI route using dvi2par technique (http://www.harbaum.org/till/dvi2par/index.shtml).
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by atul_geek » Sat Jan 12, 2013 8:00 pm
oso2k, did you get any far on this one? I am no expert but would like help if I can to get this thing working.
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by oso2k » Sat Jan 12, 2013 9:21 pm
Not yet. I was gonna buy a few with the next paycheck and start collecting the electrical components as well. I'll probably need some help figuring out the components list. Some parts on the DVI2PAR connector remain in German even after Google Chrome translates the page. I'll also need a place to fab up the board.
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by tonyrayo » Wed Mar 06, 2013 8:01 pm
Hey guys, I actually picked up 5 of these displays and was going to see if anyone at the local Hackerspace (HacDC for me) could help me out. That link to the DVI2PAR project is great though; although TI isn't providing samples for that part anymore, it shouldn't be a problem (TI has actually upgraded the part from 86 MHz to 165 MHz to support full 1080p [and even 1920x1200], which is overkill for us, however the new part has the same pinouts, voltage and timing, so I expect if any changes need to be made it would be in the code (aka the easy part).
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by oso2k » Thu Mar 07, 2013 12:54 am
Keep us upto date!
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by tonyrayo » Mon Nov 18, 2013 6:51 pm
Apologizes all around, as this is a project that fell through the cracks (also local gurus of all things electronics were even stumped by this, although to their credit this is not their forte and only one engineer had any experience with audio/video... sadly it was all on the audio side =p). I just recently returned from a 2-month business/personal trip to Japan (which turned out to be way more business than I had intended) and have a good amount of leave coming up that will take me into next year.

I'll update this post soon as I want to have a dedicated user-editable site for this project. Also there is a flexible ribbon output (as seen with many TFT-LCD screens), so I don't think it will come to direct-board soldering. I'm not sure how others feel about this, but my main goal is to create a working display. I think I finally came to terms with how the board actually reads touch input, but to actually translate that data into something the Pi could use is not something I can see easily accomplished (lol anyone good with audio pulse modulation? - since we aren't using the audio pins maybe we can come up with a cheap ADC solution x.x).
"... I've never seen the Icarus story as a lesson about the limitations of humans. I see it as a lesson about the limitations of wax as an adhesive." - Randall Munroe (xkcd)
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by mahjongg » Mon Nov 18, 2013 11:13 pm
this is a digital R/G/B+sync input LCD panel, which means that it needs a continuous stream of R/G/B values, it has no "frame buffer" of itself. That almost certainly rules out techniques used with other small LCD panels where you simply write an image into the panels frame buffer, and hardware refreshes the display. It means you want the PI to do the refreshing, (or you need to build an expensive frame buffer board like used in LCD monitors) so you need a very high band wide channel, such as the PI's DSI interface, but such hardware, ( to convert the high-speed DSI data stream to the digital R/G/B signals and sync signals ) does not exist yet.

Another solution would be a HDMI interface board, just like the ones used in LCD monitors......
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by tonyrayo » Mon Jan 13, 2014 2:34 am
mahjongg is absolutely right. I wanted to go the most direct route and have had partial success with the RA8875 Driver Board from adafruit (not bad for 2 hours of hacking, although right now it would give most people a seizure or a headache at the very least as well as other issues). Now $34.95 (without s/h + VAT if applicable) kind of defeats the purpose of using these mass-produced, cheap displays. The driver board is very generic (it even has breakout points for touchscreen data, however I believe you can still make use of the built-in driver; I haven't gotten to this point yet), which is great for testing but this means it also carries a lot of features that we don't actually need. The end should be to design a driver around a cheap micro-controller that can interface with an Arduino/Pi/etc.

My hope at this point is to first get it 100% working using the hardware I mentioned and then see what is actually needed. I was actually hoping to reverse engineer the chip used in the Tapwave Zodiac (two versions, Z1 and Z2 were released simultaneously, with the only differences being the Z2 had 4x the base memory and the units had varying colors of grey shells) but this product is hard to come by; the few out there on auction sites are going for large amounts. I can't believe a UK friend owned an N-Gage but none of my former Palm-loving friends ever bought a Zodiac (that I'm aware of at least)! Maybe when some results are posted a kind individual would donate their unit for a brief period. In the meantime I'm going to work with what I have and hunt down some technical documentation on the Zodiac itself.
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by oso2k » Mon Jan 13, 2014 3:16 am
Well..I'd be happy to get rid of my lot of these for $5 each, shipped. A little more electronics skills required than I was hoping for.
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