Is an AVR (i hav ATmega16) capable of running a touch screen?
Touch screen and AVR
Author
Message
Level: Posting Freak
Joined: Sat. Dec 17, 2005
Posts: 1659 View posts
Location: Europe- Estonia- Tallinn
which touch screen are we talking about? Depends on the interface of course.
PProbably yes tough I have not tried it.
There are resistive, capacitve and other touch systems...
You want probably use the Analog-to-Digital converter. 10Bit should be enough for the x/y position. Normally you don't have pixel resolution, I think.
Do you want to have a PC interface on the other side?
E.g. USB, RS232...
A driver is necessary.
Michael
Quote:
which touch screen are we talking about? Depends on the interface of course.
that's actually my next question. im still thinking of a project that i'll do at home, on spare time, of course. and touch screen on avr crossed my mind.
is there a touch screen readily available on the market at a very low price?
Quote:
Do you want to have a PC interface on the other side?
i don't know yet. maybe my first target is to make a touch screen run on a mega 16. i found a site using mega128. but i dont have this micro. and i think it has lots of RAM, so it is very feasible. so i was thinking, try using the mega16.
any ideas?
Level: Moderator
Joined: Mon. Jul 18, 2005
Posts: 100181 View posts
Location: (using avr-gcc in) Finchingfield, Essex, England
As Michael says, reading a touch panel is merely a matter of using a couple of ADCs if it's of the resistive variety (an Indium tin oxide "sandwich"). Perhaps more to the point is what kind of LCD panel were you hoping to use beneath the touch panel? Some LCDs are capable of being driven by an AVR (generally if the LCD is in a "module" that includes an intelligent timing generator) while some aren't (raw panels where you have to drive the H and V syncs and need a large RAm based frame buffer than most AVRs don't have the capability to hold)
Cliff
alright. Maybe i should research first on the lcd and touch screen. thanks, cliff.
Level: Raving Lunatic
Joined: Fri. Jun 11, 2004
Posts: 2405 View posts
Location: Vilanova (Barcelona)
I had interfaced LCD with touch panels easily to my STK500.
TVI Electronics sells ready made boards M16 powered with 64x128 or bigger LCD's (quite nice Optrex LCD's with contrast ratio up to 60) and (4W resistive) touch panel. Perhaps you can grasp some ideas from there.
Guillem.
What should i have to develop this project i have in mind?
i was actually thinking that the LCD and touch screen are already in one device.
Level: Raving Lunatic
Joined: Fri. Jun 11, 2004
Posts: 2405 View posts
Location: Vilanova (Barcelona)
You can find modules that have both, but usually there are two different things sold separately. That was the main reason why I ordered TVI electronics module.
Anyway, I recommend you to look your supplier's catalogs, since probably they sell modules with touch screen. There are few of them, but I alway seen that touch screen has a separate connector and you need then to handle it by yourself, althoug it is quite easy. If it is 4 wire resistive, then simply connect them directly to four analog inputs of your AVR.
Guillem.
Level: Moderator
Joined: Mon. Jul 18, 2005
Posts: 100181 View posts
Location: (using avr-gcc in) Finchingfield, Essex, England
There are modules that include both (lets face it the entire PDA industry is generally based on this!) but those tend to be the larger panels without intelligent controllers because the ARMs (usually) at the heart of PDAs tend to be those with a large LCD timing generator built onto the silicon.
However, when I was involved in the design of this:
http://www.old-computers.com/mus...
back in about 1991..1992 it was actually done with separate LCD and touch panel, the LCD was connected to and driven by the main Z180 micro while the touch panel was handled by a "slave" Z8 microcontroller that did the ADC and reported values back to the Z180 every now and again.
Cliff
Quote:
is there a touch screen readily available on the market at a very low price?
I believe this is a cheap one. Haven't tried it(yet), but someone else on this forum said he succesfully tested the touch screen with AVR chip.
http://ledsee.com/index.php?page...
Earth LCD has lots of surplus LCDs they put in 'kits'... many have touch screens
alright... thanks, guys.
anyway, i went to the site lennart specified. i'll probably be ordering the 128x64 LCD at 18euros and have it shipped here in the philippines :(. it comes with a AD7843 touch screen driver. i'll try to make a schematic if it will fit in a mega16 micro.
Quote:
it comes with a AD7843 touch screen driver
If you look at datasheet for this it is a real tiny 16-pin chip.
Since it's an A/D chip I wondered if it would be possible to use A/D in i.e. mega16. Have a look at this thread
https://www.avrfreaks.net/index.p...
Take a look at this application note, it's using the same touchscreen that you bought. It's using the avr's a/d convertor.
http://www.mcselec.com/index.php...
and here you can see the 240x128 touchscreen from ledsee in action running on M128.
http://www.youtube.com/watch?v=9...