Post by thread:9237-op lcd interface

I purchased this unit from mpja, and found their spec sheet which shows pinouts. What it doesn't describe is the method of interfacing with the unit. Anybody kn ow how to work with this device? Thanks! PS: I appreciate the replies to my rs232 question - very helpful. Get HushMail. The world's first free, fully encrypted, web-based email system. Speak freely with HushMail.... http://www.hushmail.com

Have a look at: ftp://ftp.ee.ualberta.ca/pub/cookbook/faq/lcd.doc This FAQ covers the Hitachi 44780 LCD interface, and compatibles. - Keelan >I purchased this unit from mpja, and found their spec sheet which shows >pinouts. What it doesn't describe is the method of interfacing with the >unit. Anybody know how to work with this device?

From: <spam_OUTfirewall_fredTakeThisOuTHUSHMAIL.COM> > I purchased this unit from mpja, and found their spec sheet which shows pinouts. What it doesn't describe is the method of interfacing with the unit. Anybody know how to work with this device? > Try looking at Myke Predko's website for interfacing PIC's to LCD's. There is a lot of information about what is needed to set up the interface as well as displaying characters. Take a look at: http://www.myke.com/engres/lcd.htm as well as some of his other articles at Rentron: http://www.rentron.com/pic.htm Michael Barker P.S. - How is the LCD unit? I was interested in purchasing one of these as well as the 20x1 LCD modules. Myke - hope you don't mind me plugging your sites-they've come in handy plenty for me, especially after I bought your book on PICs.

Michael: I purchased a few of these and so far, I have yet to get any of them working. On e of them may have been shot when I hooked it up in reverse - $3.95 pissed away - no biggie. Yet the other two don't seem to respond at all. I would think that even without a signal I should be able see something happen with the display whe n the LCD voltage is adjusted from 0-5V, but I see no changes. The backlight LED works great, so the worst case is they become sophisticated night-lights ;-) I'm using the 4-bit interface. I thought timing might be an issue, so I slowed t he 16F84 down to eliminate that as an issue. I can see the appropriate signals r eaching the device on my o-scope, looks like clean signals with sharp rise/fall transitions. I'm not one to give up easily, so I'll keep plugging away - if you have suggestions, I'd be really happy to hear them. Thanks! --{Original Message removed}

Fred, These displays, and any using the 44780 controller chip, are particular about the initialization routine to get them ready for use. Make sure you have properly initialized the display, and then just feed it the data, and it should work. I've used a couple of these displays, and they work fine. The key is initialization. Also, make sure you have the read/write (R/W) pin grounded. Otherwise, you'll be commanding the display to send data to the PIC instead of the other way around. Let me know if this helps you get it going. Regards, Jim {Original Message removed}

The documentation really sucks on this module, but I finally got it. My problem was that the LCD drive voltage must be NEGATIVE. Not a mention of this in the do cs - just 0 to 6VDC. As a side note I put together a simple 2 cap, 2 diode circu it to create (-)3.3 VDC from the OSC2 pin on the 16F84 (RC osc). Could also be d riven from a PORTx pin if your code allows. I haven't seen this anywhere (in rel ation to this or any other LCD module), so if you have a place to post the (12kB GIF) circuit, I'm sure others would appreciate it. Thanks for all the help from everyone that contributed. In the end I can highly recommend the 9237-op from M arlin P. Jones (http://www.mpja.com). Fred At 12:51 AM 10/9/99 -0500, you wrote: {Quote hidden}>Fred, > >These displays, and any using the 44780 controller chip, are particular >about the initialization >routine to get them ready for use. Make sure you have properly initialized >the display, and then >just feed it the data, and it should work. I've used a couple of these >displays, and they work fine. >The key is initialization. Also, make sure you have the read/write (R/W) >pin grounded. Otherwise, >you'll be commanding the display to send data to the PIC instead of the >other way around. Let me >know if this helps you get it going. > > >Regards, > > >Jim >{Original Message removed}

At 03:39 AM 10/10/99 -0400, Fred wrote: >The documentation really sucks on this module, but I finally got it. My >problem was that the LCD drive voltage must be NEGATIVE. Not a mention of >this in the docs - just 0 to 6VDC. As a side note I put together a simple 2 >cap, 2 diode circuit to create (-)3.3 VDC from the OSC2 pin on the 16F84 (RC >osc). Could also be driven from a PORTx pin if your code allows. I haven't >seen this anywhere (in relation to this or any other LCD module), so if you >have a place to post the (12kB GIF) circuit, I'm sure others would >appreciate it. Thanks for all the help from everyone that contributed. In >the end I can highly recommend the 9237-op from Marlin P. Jones >(http://www.mpja.com). I've got one of these parts, but haven't tried to interface it. The MPJ catalog references -5 V for backlight, but the spec sheet states +5 V. Apparently there are a number of conflicts in the spec. If you could post your 12k GIF file to the list (or privately), I'd appreciate it. Have you connected the backlight and contrast adjustment too? ================================================================ Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ralKILLspamlcfltd.com Least Cost Formulations, Ltd. URL: http://lcfltd.com/ 824 Timberlake Drive Tel: 757-467-0954 Virginia Beach, VA 23464-3239 Fax: 757-467-2947 "Vere scire est per causae scire" ================================================================

Fred, I'm glad to hear you got it working. And regarding you fix and findings, I have plenty of space on my website to put such things. So, if you want me to, I'll post it there and post a link on the list stating such. Send me a file with whatever you want to put in it, and I'll format it and post it to my website. Thanks and Regards, Jim {Original Message removed}

Robert A. LaBudde wrote: > I've got one of these parts, but haven't tried to interface it. The > MPJ catalog references -5 V for backlight, but the spec sheet states > +5 V. > Have you connected the backlight and contrast adjustment too? Steady on here! Don't get confused. The backlight (usually) has two quite separate connections, which may be marked plus and minus 5V. That doesn't mean it requires a negative supply - it doesn't! It means you can put a switching transistor in the negative line for logic level control. Overall, it is *entirely* separate from the logic supply. Very separate indeed, the E-L backlit boards usually had the connections at the opposite end of the board to guarantee isolation of the sundry hundred-volt supply, as do many LED backlights simply in legacy. The negative contrast voltage requires less than one milliamp and thus charge pump setups (using signal diodes, not power diodes) work fine. -- Cheers, Paul B.

Ouch, I just ordered a bunch of these. Have had absolutely no problem with 4-bit, 8-bit and serial pic setups on Powertip and Optrex units in the past, and figured that if these have a 44780 chip, they must be ok too. Hope somebody finds the solution. Has anybody confirmed they do need -5v contrast voltage? Bill Kichman, P.E. Cornwall, PA {Original Message removed}

I was going to wait for Jim to announce his site, but there's been a bunch of in terest in this - He recently posted my circuit here: http://www.jpes.com/LCD01.html The test code for this is from here: http://home1.gte.net/cramer/PIC/normpic.htm Between the two, you should be able to make it work, if not, let me know. At 09:03 PM 10/11/99 -0400, you wrote: >Ouch, I just ordered a bunch of these. Have had absolutely no problem with >4-bit, 8-bit and serial pic setups on Powertip and Optrex units in the past, >and figured that if these have a 44780 chip, they must be ok too. Hope >somebody finds the solution. Has anybody confirmed they do need -5v >contrast voltage? > >Bill Kichman, P.E. >Cornwall, PA > >{Original Message removed}