For the price, this Sony ACX705AKM color LCD module looks great for a hobby project:
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I found a datasheet for it, and the MCLK is 3.26 MHz for a 60Hz vertical refresh rate. Given that high a data rate, and the >350Kb buffer required for 242 x 162 x 3 colors x 3 bit color depth, it seems like an AVR or PIC or MSP430 is going to need some help driving it.
Is there a combination of SRAM and something to clock data from the SRAM to the LCD module that is tractable for the typical hobbyist?
Would the LCD be likely to work if it got, say, a 1 Hz refresh (MCLK at ~54 kHz), or would it flicker? (That is, does the built-in support IC buffer the input somehow?)
Don't have any real ideas for you at this point, but you might want to check out this guy's page:
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He uses a ARM chip and a Spartan FPGA, though maybe it could be done using a CPLD. To get around the buffering issue, he...ummm...soldered wires to an old SIMM. Just...loose wires. Anyway. Not many specific details on that page, but if you contacted him he'd probably be able to point you in the right direction.
Also don't forget that video chips exist which are designed just for this purpose. Many of these types of chips currently live in laptops; might be a direction to research in. Ideally you could match up the original chip that went with the PDA these were supposed to be used in.
An LCD will not be happy with a slow frame rate at all : the screen will look blank. Moreover the time spent sending each line to the LCD scan registers should be very stable, if not some lines will be lighter than others.
As an alternative to "standard" architectures with pixel memory buffer, LCD controller, etc, you can read my last article published in Circuit Cellar (September 2003, "XY Plotter") : it describes a way to drive a graphical
320x240 B&W LCD directly from a PIC, without display memory nor display controller chip. This minimalist approach is however not suitable for all applications.
Friendly yours,
Robert Lacoste - ALCIOM : The mixed signals experts
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"Happy Segfault" a écrit dans le message de news: snipped-for-privacy@posting.google.com...
Note that you could drive it at 1bpp by simply tying the LSbits low, which brings your requirement down to (242 / 8) * 162 * 3 = 15 066 bytes assuming you have enough CPU horsepower to reconstitute this "compressed" data into a usable form.
How about patching the LCD to the LCD controller outputs of this board: . It's as simple as you're really going to get short of rolling your own LCD controller in an FPGA or discrete logic. It is certainly possible to do the latter - easy, even - but then the problem becomes how to manage contention to the SRAM so that your micro can update the display. One way to achieve this is to have an "in blank" signal coming from the LCD controller, which the micro can check for before writing a data byte.
There is no framebuffer on the module. The only "buffering" is a combination of the eye's persistence-of-vision illusion, and the capacitance of the LCD's electrodes. It won't be viewable at 1Hz. Running the LCM outside its recommended frame rate also has the risk of electrolyzing the LC material and causing permanent "burn in".
Only problem is that the LED lamps did not work. I even took apart my spare to see how things were wired up. The LEDs themselves would work, but would not illuminate from the connector. If anyone else has gotten the leds to work I would be interested in hearing about it. I basically just wired in a 3.8V fixed regulator with a resister to limit the current.
Everyone has a different take on these things. My Knee-jerk reaction to it would be
CPLD and a dual port ram, nice and simple you just write to the dual port ram from your micro, and use the CPLD to generate the timing signals. This seems a reasonably easy solution to me.
As others have said here, you could use a kind of vblank signal to let the cpu access the ram, then you could get away with single port ram (cost saving), if you use reasonably fast ram and implement a 9 bit fifo in the cpld you could probably have *nearly* unrestricted access to the ram, or atleast very deterministic anyway.
You could also go the whole hog and use a Spartan or the like to drive it and use the internal block rams for your frame buffer. They are dual ported also so you have a simple job there.
Sounds like a fun project, and a good chance to play with programmable logic if you haven't done it before.
I did a project for work about a year ago using an Epson S1D1 (formerly the SEDxxx series) part with a 320x240 display. These things are really slick, they interface multiple CPU busses and display busses, some have on-board display RAM and JPEG decoders. I see some of the low end parts pop-up on ebay now and then in small lots, but nothing that grabs my interest.
I really wanted to use these parts for my personal projects, but there a pain to find in small qty. Anyone know of a distributor?
This is how it's going to be: I'm willing to give up to five people each a
25MB webspace with FTP access. The sites must be related to electronics as a hobby in some way. Personal info is ok if it's just a small bio, updates on projects etc. If you want a weblog or some extended personal journal, you'll need to find a different site and link to it; basically just keep the focus on electronics projects and info and it'll be OK.
The domain is "macetech.com" and your site will be a directory of the form "macetech.com/~yourname." The root
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is my own site, which is nothing to brag about having been neglected for some time, though a new site design is currently about 75% complete.
No hosting of copyrighted materials or software cracks, etc.,. I have a reputation that isn't completely tarnished yet, and materials I find offensive/illegal on your site will be taken down. Put it up again, and the whole account will vanish. If you want, you can have a webmail account of the form snipped-for-privacy@macetech.com, but I would greatly prefer that those accounts be used primarily for site-related and project correspondence. I don't need to deal with complaints from someone getting spammed or hate-mailed from my domain. SpamAssassin is installed, but please save bandwidth by obfuscating the address on newsgroups, and avoid signing up for stuff online with it (that's what Yahoo is for). I won't enable an email account unless you ask for it, and the inbox will be limited to 5 megs.
Follow those simple requirements (stay on-topic, don't abuse the freebies), and it's no cost to you and no ads. Currently my bandwidth is capped at 10 gigs, so if you somehow manage to exceed that and shut down mine and everyone else's site, you probably won't get a second chance. Unless your site becomes popular, I don't think you'll go over 100-300 megs a month. More than a gig, and you should look into getting your own site...you're famous. This service costs me money, and though I have no plans to drop the service or change providers, it can't be ruled out. I will notify you if a change will occur, and will attempt to continue your site on the new hosting provider if possible.
This turned out much longer than I thought, sorry for the rant! The five accounts go to the first five emails I receive with the following information: your full name, your desired username, the city/state/country you live in, and whether you need a webmail account. I'll email you when the site is set up, with the details you need to access your (electronics-related, remember) website.
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