Author Topic: LCD Controller  (Read 4655 times)

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Offline logictom

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LCD Controller
« on: January 29, 2011, 06:22:01 pm »
I've been looking at an LCD for a project but I'm having trouble finding a controller.
The LCD is WVGA(800x480) 24bpp, what I'm looking for is something that will generate all the clk, hsync, vsync R[0-7] etc etc
I've found a couple of chips but nothing that does 24bpp and a few that do WVGA at 18bpp.
I found one (SSD1963QL9) but of course that can't be bought anywhere...

If I get the LCD this is the first time I will be working with something other than the 16x2 kind of LCD so I'm not sure if I'm barking up the wrong tree.
Is this the usual route to hooking up an LCD? Micro>Controller>LCD
Is this something I should implement using a second micro? I'm planning on using it in my Renesas design for the competition and there's not enough free pins to implement the controller, plus I figured it would eat up a fair chuck of the processing power.

If anyone has any ideas, advise or even a book recommendation for this sort of stuff I'd appreciate it  :)

 

Offline jahonen

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Re: LCD Controller
« Reply #1 on: January 29, 2011, 06:28:37 pm »
Those things are usually used with a MCU with built-in LCD controller (ARM9 etc.), which takes care of all the dirty stuff. But it certainly is possible to roll your own, perhaps not with a MCU but a FPGA.

Regards,
Janne
 

Offline jahonen

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Re: LCD Controller
« Reply #2 on: January 29, 2011, 07:07:20 pm »
I like to add that those LCD's are much more difficult to drive than those character monochrome ones, since they usually do not have internal display RAM, thus needing constant refresh from a controller with clock-cycle precise timings. Pixel clock is around 25 MHz or so, which makes it very difficult to drive from a MCU without dedicated LCD controller block.

A FPGA can do it (probably you still would need external RAM for display memory) but I guess that solution is out of scope in this case.

Regards,
Janne
 

Offline CafeLogic

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Re: LCD Controller
« Reply #3 on: January 29, 2011, 09:11:27 pm »
Going from character to controller-less graphics is quite a leap. You might want to think about using one with a built in controller first. If you really want to do it. Here you go:

STM32 appnote about implementing the controller with the DMA
more info on that

PIC24 family with built in LCD Controller

My personal writeup on bit-banging it with a PIC32 (for monochrome stn)  
« Last Edit: January 29, 2011, 09:24:34 pm by CafeLogic »
 

Offline CafeLogic

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Re: LCD Controller
« Reply #4 on: January 29, 2011, 09:19:06 pm »
Just noticed your lofty resolution requirements. In that case, you might need something from the LPC1780 series. I don't know if they released it yet. Someone else was coming out with a chip with an on-board XGA controller also but I can't remember who it was, maybe Renases.
 

Offline mikeselectricstuff

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Re: LCD Controller
« Reply #5 on: January 29, 2011, 11:53:07 pm »
Because of the bandwidth needed to drive this sort of resolution, most people tend to use a more powerful MCU with onboard LCD controller, e.g. LPC2478. Another option is an intelligent display, where the graphics horsepower has been offloaded to an onboard processor that accepts high-level commands to draw lines, text etc. For example this range
If you are doing simple stuff like displaying pre-rendered bitmaps etc. or text only, then there are some cheaper options based around CPLDs or FPGAs, but these will be very applicaiton-specific.
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Offline reagle

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Re: LCD Controller
« Reply #6 on: January 30, 2011, 07:12:54 pm »
I just had to go through a similar search for a project at work. Your choice is basically an external controller from Epson (Mouser carries a lot of them), a micro with an integrated one, or a second micro bit-banging things. What I found so far are:
Freescale MCF532x series, or i.mx (those are like Cortex A8 1Ghz parts ;) ), Atmel ARM9 parts, and possibly Amulet graphics chip if you'd rather not deal with that stuff directly.  And then there is a question of graphics libraries- some chip vendors supply them, while others expect you to pay.
In your case, I'd suggest Amulet:http://www.amulettechnologies.com/products/chips.html.Plop it in, add some local flash and memory for frame buffer and talk to it serially. All images are preloaded and you don't have to deal with graphics much. An easy way out (not the cheapest, but definitely faster)
« Last Edit: January 30, 2011, 07:16:49 pm by reagle »
 

Offline logictom

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Re: LCD Controller
« Reply #7 on: January 31, 2011, 09:16:20 pm »
Thanks for all the responses!
I'm looking through all the options mentioned and weighing up the options.
When I posted I hadn't purchased an LCD but had just a bid on one on eBay which I have won so will be using that, the one mentioned in the first post.
I've just started a few different labs at uni but will be back and forth working on this and will no doubt be calling on your expert advise again:)

For anyone curious: LMS700KF07-004
 


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