Dangerous Prototypes

In development => Project logs => Topic started by: colin.i on November 08, 2011, 07:27:07 pm

Title: Super cheap touchscreen LCD
Post by: colin.i on November 08, 2011, 07:27:07 pm
Hey guys,

I just wanted to share a "project" i've been messing with lately.  A while back I noticed some cheap ($7) 240 x 160 lcds on eBay with touchscreens.  Obviously I had to buy a few of them.  Since then, they've just been sitting on my desk shelf downstairs. Just recently I got around to hooking one up and making a little proto board for it.

The thing about these LCDs is that they don't have a controller -- you have to drive them yourself with a higher powered processor (PIC32).  Luckily, Matt Bommicino from CafeLogic did all the dirty work and wrote up a sweet site (including firmware) about how to drive these screens.

(http://http://i.imgur.com/HaPvPl.jpg)
(http://http://i.imgur.com/XUjfrl.jpg)
(http://http://i.imgur.com/VX4QDl.jpg)

The coolest part of this is that I left my PicKit2 programmer at home, so I had to run it all from a ChipKit Uno32 using the default bootloader.  As you can see in the third picture (top right corner), the code uses about 25% of the processor time.  This includes a stripped-down version of Microchip's graphics library (ie clock, buttons, text, etc).

Here's the kicker:  If you already have a PIC32 lying around, this thing costs you under 15 bucks to set up!  A graphic lcd with backlight and touchscreen for <$20?!  I'll gladly share my board layout (once I fix it up for v2) if people are interested.

Link to screens: http://www.ebay.ca/itm/3-Graphic-LCD-Di ... 2314wt_905 (http://www.ebay.ca/itm/3-Graphic-LCD-Display-w-4-wire-Touch-Screen-IDW-TFS-/160487836391?pt=LH_DefaultDomain_2&hash=item255dd20ae7#ht_2314wt_905)

Link to CafeLogic: http://www.cafelogic.com/articles-2/dri ... h-a-pic32/ (http://www.cafelogic.com/articles-2/driving-a-controllerless-graphic-lcd-with-a-pic32/)
Title: Re: Super cheap touchscreen LCD
Post by: sqkybeaver on November 08, 2011, 07:36:35 pm
Fantastic thanks for sharing.
Title: Re: Super cheap touchscreen LCD
Post by: hak8or on November 09, 2011, 06:28:28 am
Very awesome find! Thanks a huge bunch!

The information that we have on the LCD is the best part, we have the pinout and everything. Also, the control mechanism is similar to how the larger LCD panels are driven.
http://www.fpga4fun.com/GraphicLCDpanel.html (http://www.fpga4fun.com/GraphicLCDpanel.html)
http://hackaday.com/2011/09/09/putting- ... h-an-fpga/ (http://hackaday.com/2011/09/09/putting-laptop-lcds-to-use-with-an-fpga/)
Title: Re: Super cheap touchscreen LCD
Post by: colin.i on November 10, 2011, 08:23:42 pm
I've been messing with the compiler optimization, and does it eve39r make a difference!

Level - Flash % - Ram % - CPU %

0 - 44 - 50 - 23.47
1 - 44 - 39 - 07.83
2 - 44 - 39 - 07.56
3 - 44 - 46 - 06.51
s - 44 - 38 - 07.63

This is with a frame rate of 30fps and a screen draw rate of 75fps.  Not only is it $15, but with optimization (I think you get up to level 2 free?) it only uses up a meager 8% of your CPU time!
Title: Re: Super cheap touchscreen LCD
Post by: Greeeg on November 10, 2011, 10:12:12 pm
Nice. I've actually got one of these screens. I'm just waiting on a breakout board for the 0.5MM ribbon cable.

This is where I'm getting the breakout, http://http://www.tplabs.info/catalog/ffcfpc-dip-20-pin-adapter/
Bought my screen from the same ebay seller.

It looks like your breakout board has the ~+20v boost converter on it. What IC are using?
Title: Re: Super cheap touchscreen LCD
Post by: colin.i on November 11, 2011, 12:15:27 am
I used a TPS61041 from TI.  As to why:  a) free samples, b) after looking at a lot of circuits, they seemed to be the simplest for the price range.  The 20v line only needs a few mA so I wanted to use a controller that was more suited to small currents.