Controlling large LCDs with a microcontroller

Discussion in 'The Projects Forum' started by El3ctroded, Oct 27, 2009.

  1. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    I'm thinking of starting a new project where I would need to display data to a large LCD. There won't be a ton of data displayed, I just need the large screen size for to display 2 or 3 pages of data in a very easy to see fashion.

    Anyway, it has to be a graphic lcd, and it should be 6-7". But the problem is how to interface with a mcu? There's a lot of good information on smaller lcds, but not so much for larger ones, nor is there much good info or sources at decent pricing. So I was thinking of maybe using a cheap 7" lcd made for automotive video...?

    As for the mcu, typically I use Pic16F series mcus for everything I do, and would hope to keep with one of them, but if required could move to a more powerful pic24 or pic32.

    I was just looking for suggestions from people who might have worked with larger lcds, or if someone knows of a site where someone documented working with them, cause all I'm finding are sites documenting character lcds or small graphic lcds.

    Thanks!
     
  2. russ_hensel

    Well-Known Member

    Jan 11, 2009
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    Look on the vendors site for spec sheets, and google for other projects using similiar technology. Or maybe someone on this site will have used them.....
     
  3. BMorse

    Senior Member

    Sep 26, 2009
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    most QVGA or TFT LCD's (may they be only 3" or 17", still have the same type of connections) although if you are going to use a uc to control it make sure you have enough pins to connect to it, and the uc should preferrably have a PMP bus (such as the Pic32MX uc's)..... see his forum about connecting LCD's to uc's >>>http://www.mypic32.com/web/guest/forums/message_boards/message/34606

    My .02
     
  4. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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  5. BMorse

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  6. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    When I mentioned in the OP about possibly using an LCD made for automotive video I was talking about one with composite input... If it works well, it would seem to be more versatile, and possibly cheaper, this way. However I do have a concern: Using NTSC, could I get a sharp image? I'm not sure if this would be a problem or not, but that 2nd link had screenshots that looked really good.

    Also, I mentioned the difficulty I was having trying to source larger LCD panels. I can find 320x240 color screens, but that's about the largest, then what I find jumps to 15" and above... I guess I could pull the LCD out of the mobile video screen and see if I can replace the NTSC circuitry... I will have to take one apart anyway to install the touchpanel. I've got a couple of the 7" mobile screens and a couple of 7" 5-wire touchpanels with USB controllers on order ($180 for 2 7" screens and 2 7" touchpanels). If I don't use them for this, I will use them in my vehicle for the kids ;)

    I'm looking all directions here. I don't want to settle on one method until I figure out what's going to be easiest/quickest. It seems the NTSC controller may be faster to get working since there's so much out there and NTSC is a standard whereas the LCD panels I've looked at (the small 320x240 ones) seem to each have differences, using slightly different controllers, even if the the interface is the same.

    Thanks
     
  7. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Try the Parallax Propeller.
     
  8. BMorse

    Senior Member

    Sep 26, 2009
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    As a display?????? The op is looking for a display not uc.
     
  9. BMorse

    Senior Member

    Sep 26, 2009
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    Are you going to be displaying in color? Is it mainly going to be text? or would Black and white be sufficient? I have some code and a circuit for producing Composite video for a TV (with the Pic32MX uc from Microchip), except I have not gotten around to doing color yet...... I was working on a project where my home automation can display messages as an overlay on the TV screen.....
     
  10. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    It will be in color. I would want it to look pretty good, but expect it to be all on a black background. There will be a bit of text, and at least 10 icons...

    I figure the text will be color, but a single color. The icons will be fairly complex.
     
  11. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Are you a seasoned programmer? If so for what?
     
  12. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    My most recent project consists of 2 boards, each with a wireless transceiver. One board uses I2C 512k serial EEPROMs and interfaces with several external devices including a thermal printer. It also uses a 16button matrix keypad, and character LCD which it accesses through an I2C port expander. The other board acts on commands received from the first.

    Another very recent project is a controller for a device that communicates with a PC via RS232 using a custom framed protocol and can configure many parameters stored in the mcu's EEPROM to alter how the controller works.

    A third project is like the 2nd but with wireless modules and a PC software interface that is controlled by the hardware.

    I use state machines and software timers a lot for my coding, and rarely use either internal or external interrupts because I just usually never need them.

    So while I wouldn't consider myself an expert, yeah, I guess I'd say I'm seasoned in C.
     
  13. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Do you want a touchscreen on it?
     
  14. El3ctroded

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    Feb 4, 2008
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    Yes, I've already mentioned that I purchased touchscreens to go with the LCDs I ordered, and have already learned how to use them by studying documentation from other projects out there.
     
  15. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    Blueroom: You mentioned the Propeller, so I checked it out. I see they have an NTSC library. It looks nice. Thinking of my needs, which are basically:
    1) output 2 pages of NTSC, each page containing about 10 icons and several lines worth of text
    2) input data from a 5-wire touchpanel
    3) control about 10 IO lines for outputs

    What would you recommend for me to purchase to quickly get started with a propeller on this project, needing to do only those 3 things?

    Thanks
     
  16. blueroomelectronics

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  17. El3ctroded

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    Feb 4, 2008
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    No, I meant, judging from my needs, which Propeller kit would be best to start out with?
     
  18. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    It's the touchscreen that'll be tricky. The propeller generates NTSC color video, I've never used one but Parallax stuff tends to be user friendly.
     
  19. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    Ah, Ok.

    As for the touchscreen, I've got a pretty through document that details how to reliably get presses, and the math behind it, so I think I'm Ok with that.

    I've found something called the "Chameleon PIC 16-Bit System" that basically uses a PIC as a master device and a Propeller as a slave with a bunch of media functions already embedded in it, looks like it will greatly simplify my project!
     
  20. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    There's also a AVR chip someone wrote code to mnake it a self contained VGA driver. I think it's open source. You could use that as the screen driver and just write the text to it with your PIC. From what I remember it does colour text too.

    This is not the driver I was thinking of but it looks pretty cool;
    http://avga.prometheus4.com/index.php?p=2-3
    [​IMG]
     
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