LCD display, connecting the dots...

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haarts
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Joined: Wed Jan 03, 2007 1:14 pm

LCD display, connecting the dots...

Post by haarts »

Hi all,

I am very new to the world of electronics and I have problems connecting a LCD display(4x40 char, type ym4004-01). The display has the correct controller and has room for 18 wires numbered 1 till 18. Now my wonderful IOWarrior24 has 16 pins... Obviously I do not know which pin I should connect to which hole on the LCD display. To make matters more interesting I do not have a datasheet for the LCD display. Are there any conventions I should follow(connect hole 1 on the LCD with pin 1?)? What is the numbering on the pins on the IOWarrior? The docs weren't quite clear(page 9, section 4.2.2 contradicts page 26, section 8.4.4, I think it is only for IOW40.)
Thanks in advance!

Harm
Guido Körber
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Post by Guido Körber »

Have a look at our application note #5: Driving Display Modules With IO-Warrior

4x40 displays usually use two controller chips. To drive this display with IOW24 requires some additional circuit (see app note 5).

If you don't have the pinout of the display module you are out of luck. You can of course just try if it follows the usual pinout but you might as well blow up the display trying this.
haarts
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Post by haarts »

I see. Looks like I do not have an alternative. What is the 'usual pinout'? for a board like this?
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Post by Guido Körber »

HD44780 based displays have the same layout for the first 14 pins of their connectors. On a dual controller module usually the E signal is moved to the pins 15 and 16 as there are two of them.
haarts
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Post by haarts »

Got it(http://en.wikipedia.org/wiki/HD44780_Character_LCD)! I should have asked Wikipedia first. Thanks for your help.
haarts
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Post by haarts »

So that means I can not use the nice male 16-pin connector on the IOW24? As pin 6 (as per wiki page in my previous post), which was the clock/E is now on the 15th and 16th pin. Then probably pin 17 and 18 are the backlight. (And now I see how I could blow up my display. :) )
Am I correct?
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Post by Guido Körber »

Yes, right. Though since quite a few displays have the connector pins in a single row you would have to do some hand soldering in any case. If you use only half of the display then wiring is not too hard using the 16 pin connector. But to drive the second chip you need to add the circuit to select the E signal.
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Post by Guido Körber »

Forgot to add: Quite a few of the connections can be found out by looking at the display. If pin 6 has no conenction then you can be sure that both E signals can be found above pin 14. Check the pins 17&18 if they are connected to anything that looks like it could be the backlight.

Though there may be an EL backlight in the module. LED backlights can be easily powered by 5V, but EL backlights need voltage boosters as they run with 70V or more.
haarts
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Post by haarts »

I am pretty sure I just have a LED backlight. So that such be OK. I'll give not connecting pin 6 a try. If I do not connect him, I should see nothing right? Then I can slowly try 15 and 16 and as soon as I found out which is carries the E signal I can hook up the backlights to the remaining pins. Okay! That should do it. Thanks again.
haarts
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Post by haarts »

On a related issue, I read in Application Notes 5 page 13 section 3.5 that I can make some additional circuitry in order to drive two hd44780 controllers. How ever I am puzzled by the 'Px.x' entry in both schemas. What do they represent? I can only find P0.0, P0.1 etc. And I can't believe 'Px.x' means 'just get any of the P pins'. Or is it?
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Post by Guido Körber »

Yes, it means to use any pin that happens to be available.
haarts
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Post by haarts »

Alright, I think I have everything connected. However I do not know how exactly use the sample program IOWarriorProber. I assume the LCD display is set on interface 0? Then I send an 'Enable LCD Mode' followed by a 'init display' followed by a 'write to display'. Is this the correct way of doing it?
haarts
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Post by haarts »

Is there anything I should see when I 'init display'?
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Post by Guido Körber »

If the contrast setting is correct you should see faint rectangles as soon as you apply power to the module. Once you initialize the module it depends on the mode you set if you will see anything. If you clear the display and don't activate the cursor you should see nothing. The rectangles should fade when you initialize the display.
elektronik12356
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Re: LCD display, connecting the dots...

Post by elektronik12356 »

Hey there,
I have 4*40 ym4004 lcd. but i dont know how to send characters(commands) to the lcd. Can u give a simple example or link a data sheet? thank you...
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