TFT LCD - how to hack 'em?

[Hank Fletcher]

So 7" TFT LCD photo frames are for sale now for around $60, which begs the question: Why aren't we hacking them? A full colour, cool looking display, an SD card reader, and the remote control to boot - seems like a good deal for the price to me!

I've seen video on Youtube of a guy working through a "How to Make Your Own Video Game System" guide. He's using a CRT for the display, though, but the heart of his VGS is just an Atmel mcu. I think it's time to upgrade our hacking skills, and get a PIC running some DIY graphics on a photo frame.

Uh... anyone know where I can start? I'm having trouble finding any info on a project like this. Links, advice, speculations, usual digressions... it's all good, baby!

 

[ArtemisGoldfish]

What sort of hack are you expecting from it? Just a software hack, or being able to utilize the screen seperately?

 

[Mike - K8LH]

I've fantisized about the same thing Hank, but like you I have no idea where to start.

Mike

 

[AtomSoft]

This is what i like seeing.. Someone noticing a nice lard LCD for so cheap just used on another product. I own some LCDs and GLCDs from cellphones and wish i knew how to hack it to use it for my own selfish purpose lol. Hopefully someone with some know how will pop up and share some info...

 

[Hank Fletcher]

I'm more of an end-results kind of guy, even knowing the dangers of that characterizing me as a charlatan - but hey, I is what I is. The deal is, I don't care at what level I'm hacking, as long as it does what I want, and is a) cheap, and b) easy. I'm more goal-oriented than process-interested, if you follow me. If I learn something about the process on the way to my goal (which I invariably do), than that's groovy, too.

So I think the goal with the TFT LCD is to just do what we've being doing with 7-segs, LED matrixes, and LCD text displays, only bigger, better, and (relatively) cheaper. The goal is to be able to display characters or graphics, even just simple ones, using little more than a cheap mcu and the hacked display. Part of the learning process (or learning about the process, if you will), will be figuring out what we can get for the least amount of cash and effort.

We could expand our experiments to include interfacing with composite video or VGA monitors. I noticed (through searching this forum for "composite video") that there was someone else who was recently interested in this, too. The idea is striking a compromise between what's cheap and what's easy. If it's easy, but it's too expensive, than it's no good. If it's cheap, but the amount of work is so involved that I'm essentially building things from scratch, it's no good. So I'm thinking experiments with old CRT VGA monitors (cheap as free), or if composite video or some other interface works better, we might consider some of the automotive video devices that are available for <$100 now (many include several interface options on one device).

I really like the VGA option. No matter where you are right now, you're probably within 50' of a VGA CRT monitor nobody wants anymore. Fodder for experiments, I say, but instead of tearing the thing apart, why not find out what happens when we start fiddling with the connect pins? Plug it into the wall, you don't have to fiddle with the AC power, just tinker with the connector pins.

I like the VGA CRT digression, because the follow-up could be using a small (like 15") LCD monitor that has a VGA connector. I appreciate that from an engineering stand-point, it's all topsy-turvy, because you'd be using a digital mcu (like a PIC) to interface a digital monitor (the LCD monitor) via an analog connection (or is the VGA connector pseudo-analog... it could be considered digital if you just wanted to have black and white or a handful of colour options). The way things are going market-wise with monitors, it's not going to be long before 15" LCD monitors are cheap-as-free. Re-use, Recycle... Hack!

The other thing I like about the DIY VGA signal digression (the first being that it's as cheap as nothing) is that I know it can be done (that is, that it must be relatively easy). There are some Youtube videos of guys doing weird things to the horizontal and vertical control of their old monitors, but this one is the only one along the lines of what I'm looking for (at least what I could find):
YouTube - Lesson 7: Experiments 2, 3 & 4.

By the way, the correspondence course this guy's working through looks wicked-awesome, so I recommend checking out the link to the lesson source (it's in the description to either his first or last lesson video, I can't remember. They're all worth watching, so you won't mind looking for it!). For less than $400 bucks you get all the gear and instruction material you need to do what he's doing (minus the monitor, I think, but that's no biggy). He's using the SX28 chip to make that Break-Out style game, and you gotta admit, it looks pretty cool considering the small amount of parts he's using to make it happen.

Apparently the SX28 is like a PIC on steroids, but other than the fact that it's faster (like about 100MHz), it doesn't seem to have anything more in the way of features beyond what's in the PICs most of us are using here. I'm convinced you can do it with a PIC - it might be monochrome, it might not be high-res, but you can do something, I'm sure of it. I see there are some RF signal PICs, but I'm not going there for this right now. I'm talking cheap, common, easy PICs.

Just because the VGA protocol (that is, coming out of VGA driver card) is 640x480 and a ton of colours, doesn't mean that we can't come up with our own PIC driver to connect to the VGA monitor. So we'll simplify: drop the colours, drop the resolution, maybe even drop the vertical frequency. Still, doesn't it seem like we ought to be able to drive the monitor with at least the resolution and frequency that some folks have worked out for various, smaller LCD graphical displays?

This is what I've learned so far after an evening of surfing and reading. The VGA connector (VGA pinout and signals @ pinouts.ru) has three pins for red, green, and blue respectively (RGB), and a common pin for each of those. Sending 0V to any RGB pin will result in nothing happening (so a black screen if all RGB pins are constantly 0V), and sending 0.7V to any RGB pin will result in maximum luminescence (is that the right word for it?). If you constantly send 0.7V to all RGB pins at the same time, the result will be a white screen. We could just use voltage divider resistors to get the TTL outputs from a PIC down to 0.7V, and if someone wanted to get really fancy (and crossing your fingers that the PIC would be fast enough) make a R2R ladder to fine tune each RGB for a greater variety of colour mixes.

There are three more pins I think you need, and that's it. They are: the horizontal sync, the vertical sync, and the sync ground, and unlike the RGB pins, they're all TTL level voltages (so could be connected directly to a PIC's TTL output, I think). What exactly you have to do with the horizontal and vertical sync, I'm not entirely sure.

This is where the rubber hits the road with the hack: to what extent do we have to conform to the VGA protocol in order to get reasonable images on the screen? Maybe someone else can pick up the torch on this, and chime in with their two cents on timing the signals.

For that matter, if anyone wants to chime in with questions, comments, or even just to call me out on what I've said here, please do - it's all part of the fun!

 

[blueroomelectronics]

Another poster pointed out this site but it may be of interest
**broken link removed**

 

[Hank Fletcher]

PS:
Is there anyone out there in a more civilized city that might have a local electronics shop selling the DB15 female connector? If I'm breaking out VGA to a PIC, I'd rather use that than fray a cord! If you'd be so kind to pick up and send me one, I can pay in cash or karma. PM me, kind soul, and we'll work it out.

 

[Leftyretro]

I seem to recall that the propeller chip has built in support for a VGA interface, could make a cheap driver for a vga type display.

**broken link removed**

Lefty

 

[Hank Fletcher]

Another poster pointed out this site but it may be of interest
PICcoder - VGA clock with USB interface

Ooo... thanks!

 

[3v0]

Been thinking about this.

Along with the old VGA monitors there are as many or more old VGA graphics cards. One could talk to such a card with a PIC and let the card drive the monitor.

 

[Hank Fletcher]

I hopped via blueroom's suggestion to this link, which is really close to what I was talking about (he even describes the SX28 the same way I did - PIC on steroids!):
**broken link removed**

See, I told you it could be done!

 

[blueroomelectronics]

The book learning to fly the 24F includes an NTSC program & schematic for the powerful 24F series PIC. I was thinking of a dsPIC30F3013 version as this too has plenty of power maybe even enough for a colourburst signal.

 

[Hank Fletcher]

Been thinking about this.

Along with the old VGA monitors there are as many or more old VGA graphics cards. One could talk to such a card with a PIC and let the card drive the monitor.

That sounds like a good idea, too! Hacking a VGA card: something else to surf for...

 

[ArtemisGoldfish]

Hmm, yeah, it is an interesting idea, but the whole completely digital nature of those little LCD screens that they use in digital picture frames might be a problem (Possibly requiring a dsPIC for it's signal processing power?) You could always pick up one of those cheap little keyring photo viewers with the LCD screen and start off with that, though I wouldn't be surprised in the least if those just use glop-top chips.

 

[Blueteeth]

Some idea's

Photo frame:
I think it would be easier to go down the logic route, with CPLD's FPGA's. Most tft's have a 6-8 bit interface with simple sync control lines, that could be implemented as counters. As long as the CPLD/FPGA reads from frame memory (SRAM/DRAM) and keeps the display refreshed, you could just write to the RAM and it will be displayed. Advantage is, its all digital...but if you want to display video, moving pictures...it gets tricky as in the digital world thats a hell of a lot of data to move around.

Converting it to VGA would need fast ADC's, fast RAM (one for each colour) and logic to control it all. Its doable, but tricky.

TFT with VGA interface. Yep, MCU's can do this, but even AVR's have limit the resolution/framerate. And of course, VGA needs refreshing (doesn't have permenant frame memory, only a buffer). Faster MCU's will do the job nicely...but sitll tricky for displaying mulitple colours in a small area.

Blueteeth

 

[HFTekk]

So I've just got my dirty little hands on an in-dash entertainment system, which includes a 7# TFT-LCD display, with a touch panel. I want to hack this so bad, but am finding almost zero information on how to start. Has anyone made any progress on this in the two years since the last post was made?

 

[Hank Fletcher]

Hmm... been a long time since I've been on this forum...

The short answer: no. I kind of abandonned this project in favour of others. Microchip make MCUs dedicated to the task, and at the time of my peak interested, I was perusing their copious documents specific to display design, so might try that for a "from scratch" approach.

Kronos robotics (I think) at one time had a neat 'n' cheap packaged solution for small (cell-phone) size displays, which also used SD memory cards for holding the video info.

Hope that's some help - good luck, and have fun!

 

[Hank Fletcher]

And this guy really seems to know what he's doing:
YouTube - Kdg86's Channel