SED1335 320x240 LCD

[Demon]

I've found the datasheet, the SED1335 is part of the SED1330 group.

But there's tons of settings in there, many I'm sure I don't even need to worry about. I found some code over at CompSys though, so that should be a great help.

Now I'm waiting for the LCDs to come in so I can make some tests.

Robert

[Demon]

Ok, the LCDs came in and I figured out all the system settings.

LCD datasheet here (if you can call it that):
http://www.qingyun-it.com/products/y...LCM3202401.pdf

SED1335 controller datasheet here:
http://www.compsys1.com/support/docs/sed1330.pdf

I am driving it with a PIC 16F877 at 20MHz. Every thing goes fine, I can reprogram it over and over and change the text at will. But if I power OFF and back ON again the LCD goes crazy. It's like a TV that loses vertical control, just a blur of lines going super fast. If I wait 7 seconds or more before powering back ON everything boots up normal.

This is the 1st type of LCD controller that's ever done that to me and this is the 4th type I've tried so far. Has anyone ever encountered a similar problem? I'm guestimating that this particular controller requires a short break between power OFF and ON for some technical reason, why? No idea but that's what it looks like.

The initialization routine in the PIC seems fine 'cause it works perfectly if I wait 7 seconds or more. I can pull-down /MCLR as often as I want, the PIC resets fine and the LCD displays properly.

My rookie solution would be to control the power-up of the LCD with the PIC instead of feeding it directly from the supply line. A 10 second 'warm-up' period with a flashing LED and probably a transistor to power the LCD. The LCD datasheet says 90-100mA, that's more than what a PIC pin can drive (25mA if I read the datasheet properly). I was thinking of having the VDD direct to the LCD logic, and placing a transistor on the Vss like so (just to confirm I have my head on straight):

Base: control pin on PIC via a resistor, not sure what size but I know I need one.
Collector: LCD logic
Emitter: VSS

Does that make sense?

Robert

[mister_e]

Those are perfect for small and close to be obsolete products IMHO. Have a look to newer controller and LCDs. Varitronix do some really great.

I've never work wit those SED133X so far so i can't comment on. 7 Seconds seems to be a huge delay... maybe the initialisation is not done properly.

Those i used, needed less than seconds for a safe start-up delay.

In meantime, some GLCD are quite noise sensitive. May some 10uF tantalum + usual 0.1uF on VCC and as close as possible of the module could help.

I don't think that powering the LCD as you said will solve or help. Be sure of your LCD init timing.

That's all i see now.

[Demon]

Turns out it wasn't the LCD at all causing the problems, it was the PC power supply that I use on my bench.

If I take the wire to VDD. I can turn the circuit on and off real quick. I suppose the power supply was surging or something, not worried 'cause now I know not to do that.

Steve, I like this LCD 'cause it is affordable and easily available.

Robert