Results 1 to 10 of 10

Thread: Troubleshooting an HD44780? 20x4 char LCD

  1. #1
    Newbie
    Join Date
    Mar 2004
    Posts
    15

    Question Troubleshooting an HD44780? 20x4 char LCD

    Hello, I recently bought a charactor LCD and wired it up according to the ever so poular wiring diagram for parallel port with the 100k /10k pots. I turned everything on, adjusted the controls, and boom! I get the familiar 2 solid line default screen. Good start. I proceed to plug it into 2 different computers (XP/winamp/LCDdisplay and dos/MPXPlay) and try every bios setting for parallel ports, and even cut my 22ft parallel port cable down to 7ft.

    Not once have I gotten anything but those two solid bars. Do you guys have any ideas on what I could try or what I could setup to test to see if the thing should be working, and what I need to do to get MPXPlay to use it? I also adjusted all of the settings in the .ini file to no avail.

    I might try to get a couple bucks on ebay for it, and then buy a new one, but I am afraid that the same thing will happen the new one...

    Any help on diagonising my problem would be appreciated!

    Dwiel

  2. #2
    Low Bitrate BeamRider's Avatar
    Join Date
    Apr 2004
    Location
    Genova, I
    Posts
    92
    Hi
    I don't know your software but with my 20x4 I use jaLCDs.
    Most LCD control software need a portdriver installed to work and frequently it has to be installed manually.
    Look on the jaLCDs site and try with this software before buying another LCD

  3. #3
    Newbie
    Join Date
    Mar 2004
    Posts
    15
    That LCD software is obviously for windows, but I only have Windows XP and DOS. I wanted DOS on my carputer for quick boot times, but should I install windows 98 JUST so I can try using software with it to test my LCD? I'll do that if that is the next logical step. I was just wondering if that program you refered me to handles XP... I did a quick look around that site and found that it is in anther language, so I couldn't really get much use other than the software itself.

    Thanks for the quick response. I am gonna try the LCD with XP and then if that doesn't work, I'll go ahead and install 98 on my carputer.

    Any other ideas?

    Dwiel

  4. #4
    Maximum Bitrate Marsupial's Avatar
    Join Date
    Feb 2004
    Location
    Montreal
    Posts
    763
    I don't know any DOS applications for HD44780, but if you're to run it into XP, there is a need for a port extension
    see
    http://www.driverlinx.com/DownLoad/DlPortIO.htm
    named port95nt.

    If you haven't done that, you'll never get anything else then the test bars...
    -Mars

  5. #5
    Newbie
    Join Date
    Mar 2004
    Posts
    15
    I have tried that before, and just to make sure, I just reinstalled it, and tried running jaLCDs. I am still only getting black bars.

    I am installing 98 on my carputer as I type, and should be able to try that tommarow. My plan once I got 98 running was to first try winamp 2 + vis_LCDisp. I can also try jaLCDs.

    What else can I do to get this thing working?

    Thanks for the help thus far!

    Dwiel

  6. #6
    Newbie
    Join Date
    Mar 2004
    Posts
    15
    I can still not get my LCD out of the test pattern mode. :-( I installed Windows 98 on my target carputer, and have tried jaLCD, winamp plugin, etc. Does anyone have any more ideas?

    Thanks!

  7. #7
    FLAC Chairboy's Avatar
    Join Date
    Jan 2004
    Posts
    1,380
    I've made some hd44780 for microcontrollers, and I seem to remember putting a potentiometer on one line to play with the contrast. Your problem could be misadjusted contrast. Have you played with that pot once it's powered up?

  8. #8
    Newbie
    Join Date
    Mar 2004
    Posts
    15
    what would need to change? I currently have tried with the contrast at full and at low. What would I be doing as I adjust the contrast? Just keep clicking the button to retry to connect/display I take it?

    thx

  9. #9
    Maximum Bitrate Marsupial's Avatar
    Join Date
    Feb 2004
    Location
    Montreal
    Posts
    763
    what schematics have you used - seams its a circuit prob to me

    check this one



    also do continuity test on all connections and verify for shorts.

    What have you done so far to test the circuit?
    -Mars

  10. #10
    Newbie
    Join Date
    Mar 2004
    Posts
    15

    Post

    Thanks for the pic. I just checked the ciruit diagram I was using against your and they are the same. The one that I am using is at: http://www.myrolypoly.com/lcd_projec.../lcd-db25.gif:

    I will go ahead and test for shorts, but I believe I have done this before. I think I will also test all of the connections going from the LCD to the male printer plug. I have tested from the end of the parallel port to the male end and from the wires comming from the LCD connecting to the parallel cable, but never the whole thing at once. Should be the same, but it can't hurt.

    I was also going to test the parallel port out, but I didn't know what kind of software I could use this to test it with the voltmeter. Actually, now that I think of it, I can easily do this myself using the _outp() function in C++. I'll code up a quick test tonight and try to test it. The only computer I have Win 98 on is a bit flaky so I do not yet trust the parallel port.

    I'll hopefully get back to you with what was causing the problems ;-)

    Dwiel

Similar Threads

  1. USB -> Parallel -> HD44780 LCD
    By Zip-Lock in forum General Hardware Discussion
    Replies: 5
    Last Post: 03-09-2005, 06:31 AM
  2. Replies: 0
    Last Post: 07-24-2003, 03:42 PM
  3. GPS DATA on HD44780 char Display ??
    By felix99 in forum GPS
    Replies: 8
    Last Post: 01-10-2003, 05:56 PM
  4. 4x40 char LCD EL backlight & inverter. sell or trade...
    By Jarrod in forum Classified Archive
    Replies: 6
    Last Post: 03-06-2002, 10:31 AM
  5. 20x4 inverted char. LCD and x-10 mouseremote for sale
    By JustAGuy in forum Classified Archive
    Replies: 8
    Last Post: 07-27-2001, 03:51 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •