LCDInfo.com

I don't use the read function but i need a free pin on the lpt to control the backlight. So R/W must be grounded.

Ok I`ve been doing some testing and changes with my LCD with Syridian, and found intresting things....

He found up that some SED1520 controllers need a 18Khz external clock, and some others need 2Khz clock.

Found some things on the schematic that did not seem right and changed them, the really bad thing is tat powertip datasheets don`t have a lot of information; I`ve written an e mail to their sale department (since i could not find any other adress) and told them about the issue of finding out if a 18khz is needed or a 2khz...

Any help with the schematic is welcome, the only thing we got LCDinfo to display was some random lines I will look somewhere to host the small video file showing the random lines...

http://www.laneros.com/attachment.php?a ... ntid=12500

Keep in touch!

did an experiment today...

I set the frecuency lower than 2Khz, and a line came up, a line from the top side of the display and you can see it going down all the way to the bottom.

no text was displayed, but several smal pixels from the line where missing.

It did not matter if LCDinfo was running or not, th e line kept going and going...

Any help will be most welcome...

NEW development...

Finally saw something on screen...

The weird thing is that it worked ant a CL frecuency of 130Hz...

Another thing, when I set the clock to a higher frecuency, everything disapears...Can see anything...

Been thinking something out...I`ve masured voltages on the pins of the LCD while working...
And got this results.

Pin 3 which controls contrast is set to darkest contrast (but can`t get the whole screen black) has a voltage of - 0.03V (yes with a minus), so i`ve been thinking that maybe the contrast control needs a negative power supply to get very dark contrasts...

Another thing...

The RES pin is at 4.71V
Pin 4 Ao 4V
pin 5 CS1 at -0.19V
pin 6 CS2 at -0.20V
pin 7 CL at 2.46V
Pin 8 E at 4.7V
pin 9 RW at -0.03V
Pins 10 to 17 at -0.20V
Pin 18 RES at 4.71V
pin 19 and 20 are backlight which are disconected

I can see text displaying on the left side of the LCD, but on the right side, I see random pixels don`t know if the display is damaged, but I think that maybe is a driver issue because of the lowe CL frecuency...

I will try to conect a negative supply to the contrsta control and raise the frecuency to see if anything changes...

Here is an image of what it shows...if any help...
http://www.laneros.com/attachment.php?a ... 2548&stc=1

I have recorded a small video of what it shows too, so if anyone wants it PM me and I`ll send it to you...


Any help please...

Call me a worry wort... But that -0.2 of a volt on some of those connections seems to me to indicate that the GND of the parrallel port and the GND of the 5Volt supply are not tied together properly. This is strange, as you are using the computer powersupply, and therefor all GNDs should be equal.

Maybe try tying the LPT port GND directly to the LCD GND, this should also bring up your supply to arround 4.9V, as that 0.2 volts is a GND offset. While this shoudn't be causing your problem... While you still have a problem, everything should be made perfect.

_________________
Syridian,
http://syridian.com

pin 18 of the LPT which is GND is tied up with GND of OSC and LCD...

1. What do you think about the error on CS2?, this morning I powered on the LCD and the text was writen in the lower part of the CS2...

2. Any explanation about the 130hz?
3. Can I put a negative voltage source for contrast adjust?

Thanks...

Yes, weired. Syridian what did you use?
I had worked on the driver and changed the wiring this weekend. But with no result. Did not get any useful on the display. I'll build up the hareware again to make sure it's not a hardware problem.

Just wondering...does anyone her have this same Display??

Would really help...

I think the driver is not comunicating well with CS2, maybe because of the CL signal...

Hmm Well.. I must admit.. I actually used a Frequency Generator here at work. And I must admit also it actually provided a squarewave signal that was -2.5Volts to +2.5Volts, not 0Volts to 5Volts. Maybe that could make the differance? However if I changed the frequency too much either side of the 2Khz, the screen lost sync, at first it would just go like a bad TV reception, and then it would loose it totally.

I wish we weren't so busy here at work... Cause then I could play with it again... I'll try to find some time to make up a 555 circuit, and try that in the next few days. If that gives me the same problem you two are having, then we will know that the OSC signal is the cause.

Anyway... gotta get back to work...

_________________
Syridian,
http://syridian.com

Did not get this thing to work
My 555 gives me about 1.5kHz. This may be the problem or i destroyed the lcd or what ever...
But i hope i could help you, by giving the source of the driver for the other type of SED1520 controlled lcd (the 18pin one).

So send my you email in a PM. BTW it's a MS Visual C++ project.

There are some things you have to change, because the 18pin lcd react a little bit different. As distinct from your 20pin the 18pin need a high level on CS1 and CS2. And the driver did not control the RW or WD pin.

Thanks for your help...

Have a question, can the 555 make a negative and positive square wave? like Syridian`s?? -2.5V and 2.5V, maybe that is the whole problem of the LCD....

It can't.. but you could ofset the GND just to the 555 circuit by 2.5Volts, this would effectivly give you the same signal.

_________________
Syridian,
http://syridian.com

jsc69,

The source is available in the developers section.

Just been gong through it, and there seems to be either some corruption in the file, or some strange characters in there. Looks to me like some of the newline control has been changed or something.

Anyway... Be interested to see if the code you have has these same errors. I'm not really sure if they would affect the compiling of the source though, maybe just the readablilty.

_________________
Syridian,
http://syridian.com

I will try to make the OSC make negative and positive wave, but my programming is as bad as my russian!!!

a teacher at my university asked me ant what speed was the driver sending the info to the controller...did not know...

but he told me that it must be around 126ms, between the train information waggons as he explained it to me...

Any answer?

thanks