Large LCD to display images

I am fairly new to Arduino (not to programming or electronics in general), but I am looking to create a device that will display images (doesn't matter the ultimate format, jpeg, gif, bmp whatever is best) on a large LCD using the Arduino (if possible).

Basically LCD would be color and hopefully 10"+. Resolution isn't as important, but must be legible. 640x480 something like that.

General Purpose is to create a rotating display of announcements without a PC.

Images can be loaded on a memory card and can handle that part.

Mainly has anyone been able to display images using arduino on a large screen?

I see lots of examples on small under 5" screens.

Any thoughts on how I could make this happen on a large screen or what screens would be ideal?

Simply a large digital picture frame.

Thanks, Regulus

This is an excellent start thanks Richard. Now I just need to figure out the rest of it.

I hadn't thought of TV out, definitely an easier solution.

Thanks, Chris

Well, maybe.

It's actually quite difficult to create good looking text displays on TVs. I suspect that it's hard enough that an Arduino doesn't have the horsepower to do it

You probably can do it with a digital monitor and a computer display, although it won't be easy.

You also have memory problems. You need to have memory for the frame buffer (640 x 480 x whatever number of bits per pixel you need) and you need to have a character set memory, which could be read only.

The only really good way this works, assuming that the announcements just flash change from one to the other, is to have a double buffer frame memory, where you write one while you display the other, and flip to the other buffer when you change to the next announcement.

Okay, maybe you understand it, but let's tell the folks at home what we are talking about.

In a TV, the bandwidth of the video channel is limited, and has some fairly non obvious ways to specify color. Even HDTV, which is much better than standard TV has these problems.

Anything with a very sharp edge has "issues" when the bandwidth is limited. Character generators for TV stations have very complex shapes that don't have sharp edges, and know what the effects of the transitions they do make are on the monitors. That is why they look good, even over complex backgrounds.

When you build a system that JUST displays text, your problems are somewhat simpler, but you can't just use a 'binary' character set. The edges need to be smoothed. If it's just characters against a simple color background, then the character set ROM has to be carefully constructed, but using it is easy: it really is just a block copy of the character into the frame buffer.

This means you need more bits per pixel then you might otherwise think, in both the frame buffer and the character set ROM, and making up the character set is not simple.

With a computer monitor, there is enough bandwidth, and you can use very simple frame buffers and character sets. As a result, you have fewer memory operations.

without a PC

Does that mean "without a bulky box"? Or "I want the challenge of creating graphics without the luxury of PC hardware"?

If it's the former, I've got some old tablet PCs like Fujitsu Stylistics and Points, and some internet appliances, that have PC(-like) capabilities without the PC form. They might be suitable to your purposes, and I have more than I need (or, some would say, "ought to have" ;D) at the moment. Drop me a PM or email if you're interested.

I know it's nice to tinker and create but what you talking about is a digital picture frame, £20 from tesco's, they also sell a 2.4" digi pic frame for less than £10, i bought one it has a nice 320x240 RGB LCD in it, better still it has an 8bit data bus

Interesting. Well, my actual problem to solve is as follows:

remote location of these electronic slide shows of announcements / ads / whatever. They need to be cheap. Need to have very little maintenance (pc's tend to need lots of care and feeding). Small is a bonus since it will need to attach small kiosk devices.

I could easily create a PC version on a laptop or tablet but they will get expensive if I need to setup 500 of them.

Arduino probably isn't the right solution unfortunately, probably a single board computer is better but they are $150 for just the board and like using a sledge hammer to push in a thumbtack.

Chris

yes it is basically a digital picture frame. but that was just the surface of what the application is going to be used for. Maybe I need to look into the ability to hack a digital frame instead of approaching it from this angle.

Hi Regulus, Don't let me put you off your quest, i love hardware hacking but sometimes the product is already right in front of you, i have 5 digi pic frames scattered around my shop displaying special offers, they are a good eye catcher, there is quite a bit of info on digi pic frame hacking if you digg deep enough, www.hackaday.com is a good start.

pc's tend to need lots of care and feeding

Bah: Windoze PCs need "lots of care". Put a real OS on the same hardware, and it can run for years without intervention.

If you're really going to do 500 or more of these, you'll probably want to design your own hardware to save unit costs. Or cut a deal with someone making digital photo frames to open the kimono and let you put your custom firmware on their hardware.

It's fairly likely that some of the photo frames on the market have an SPI on their CPU chip, which would let you attach a Wiznet or Microchip Ethernet module to give you a convenient internet interface. Google for hacked picture frames, and you'll probably find that someone has done a bunch of work that will give you a huge head start.