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PostPosted: Sun Feb 29, 2004 22:39 
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Joined: Thu Feb 26, 2004 1:40
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Location: Stockholm, Sweden
no that's with load.. without load I got like 0V.. strange i think..

what should i use to boost my voltage at my LPT pin 7 then?

btw.. can I use 74AC245 or 74HC245 instead of 74CLX245 or 74LVC245?


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PostPosted: Sun Feb 29, 2004 23:27 
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Joined: Sun May 05, 2002 22:05
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Location: Lappeenranta, Finland
Are you sure that the LPT port pin was driven high when you measured 0V ? The PCD8544 driver drives pin 7 high when it's selected and LCDInfo is running. When LCDInfo is closed PCD8544 driver takes pin 7 low again.

It's also possible that your parallel port isn't able to source enough current to power the lcd and that's why voltage drops.

Possible variation of the schematic presented in this thread would be to power the regulator from some external source instead of LPT port pin 7 and then route the LPT port pin 7 to one of the 3 unused inputs of the 74LCX245 and also route the lcd V+ pin to the corresponding 74LCX245 output. The reason doing it this way instead of wiring the lcd V+ straight to the regulator is that according to PCD8544 datasheet a proper startup sequence must be done just after powerup to not damage the display and this is only possible when the LCDInfo driver can control the V+ line of the lcd.

You could also control the V+ line using a transistor or fet but I think 74LCX245 outputs should be able to source enough current so there wouldn't be need for extra parts.

I can't recommend 74HC245 or 74AC245 because they're not spec'd for 5v input logic levels with 3.3v operating voltage.


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 Post subject:
PostPosted: Sun Feb 29, 2004 23:47 
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Location: Stockholm, Sweden
okay..
I think I got it.. but then I need something to get my voltage a bit higher than 2.15..

what component would you recommend to like boost it up 1.5 or 2?


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 Post subject:
PostPosted: Mon Mar 01, 2004 0:04 
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Location: Lappeenranta, Finland
The 74LCX245 would work as the buffer/booster in the connection I described in my previous post.

If the parallel port voltage drops because it's not able to source enough current then adding anything there without external power source would only make things worse.

But before deciding what to do you should first figure out what your parallel port outputs without load.


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PostPosted: Mon Mar 01, 2004 0:25 
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Joined: Thu Feb 26, 2004 1:40
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Location: Stockholm, Sweden
I digged in my box for my multimeter and found it :)
my output without load now is 0.14 and with load 4.23 on pin 7
on pin 1 it's w.o. load 4.23 and w. 4.27


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 Post subject:
PostPosted: Thu Mar 04, 2004 23:58 
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Joined: Sun May 05, 2002 22:05
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Location: Lappeenranta, Finland
Your voltage without load on pin 7 is still strange. So this is without anything connected to the parallel port and the pin driven high by software ? Your other voltage readings look fine. It's still possible that your parallel port is not able to source enough current to drive the display and circuit.


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 Post subject:
PostPosted: Fri Mar 05, 2004 10:48 
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Joined: Thu Feb 26, 2004 1:40
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Location: Stockholm, Sweden
henri:
got my display working..
Image

thanks anyway..

yes my voltage is a bit strange on my pin7.. but who cares?


-------------------
ADMIN EDIT:
jetage reported me that his display died using this schematic. So others might not want to try this one.


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PostPosted: Fri Mar 05, 2004 11:25 
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Joined: Sun May 05, 2002 22:05
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Location: Lappeenranta, Finland
Glad to hear that your display is working. Looks like you then decided to just connect the LPT port pins to the display inputs without extra level conversion. Like I mentioned in some of my earlier post in this thread it should work but it's possible that the display doesn't like it in longer use. But it's not very expensive display after all. ;)

A little addition to your connection could be some current limiting resistors to the data lines (lpt 2-6). Maybe few hundred ohms or 1Kohm or something like that.


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 Post subject:
PostPosted: Sat Mar 06, 2004 12:19 
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I think it's like you said..

What if I add the resistors then?
Will it work for longer or do you think the lifetime will be the same?


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 Post subject:
PostPosted: Sun Mar 07, 2004 0:07 
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Joined: Tue Feb 18, 2003 23:28
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they will protect the lpt lines ... nothing more :D


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 Post subject:
PostPosted: Mon Mar 08, 2004 16:29 
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Joined: Sun May 05, 2002 22:05
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Location: Lappeenranta, Finland
Also the resistors should limit the current flowing from lpt port pins to the lcd pins.

But I can't say anything definitive of how well it would work as I've only tested it the way described on the first page of this thread.


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 Post subject: Re: PCD8544 (Nokia LCD)
PostPosted: Wed Mar 10, 2004 16:00 
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Joined: Wed Mar 10, 2004 15:58
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Location: Sweden
Henri wrote:
I have a Nokia 3310 display interfaced to LPT port and experimental LCDInfo driver for it running.
Image
how much ohm do u have , so u don´t burn ur nice lcd :) it´s fantastic , keep up the good work 8)


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 Post subject: Re: PCD8544 (Nokia LCD)
PostPosted: Thu Mar 11, 2004 15:26 
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Location: Lappeenranta, Finland
c0rn wrote:
how much ohm do u have , so u don´t burn ur nice lcd :) it´s fantastic , keep up the good work 8)

I don't have any ohm as I don't use resistors. I'm using the 74LCX245 chip for the logic level conversion.


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 Post subject: Re: PCD8544 (Nokia LCD)
PostPosted: Thu Mar 11, 2004 19:13 
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Joined: Wed Mar 10, 2004 15:58
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Location: Sweden
Henri wrote:
c0rn wrote:
how much ohm do u have , so u don´t burn ur nice lcd :) it´s fantastic , keep up the good work 8)

I don't have any ohm as I don't use resistors. I'm using the 74LCX245 chip for the logic level conversion.
hmmm okej. I follow jetage schema :p , how much ohm do i need :)


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 Post subject: Re: PCD8544 (Nokia LCD)
PostPosted: Sat Mar 13, 2004 11:31 
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Joined: Sun May 05, 2002 22:05
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Location: Lappeenranta, Finland
c0rn wrote:
hmmm okej. I follow jetage schema :p , how much ohm do i need :)

Maybe 1kohm. But I've never tried this so I can't give any quaranties how it will work.


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