LCD Control

[boboco]

Hi Steve, Hi Alec,

Alec, I've tried all sorts of delays, or even different program parts, to write line 2, all without success, but thanks anyway.

Steve, I usually allow 1 sec. startup, but trying 2 secs made no difference. The setup is a control circuit for medical laser x-y-z control containing analog and digital circuits. This model is supplied via laboratory power supply, is smoothed and filtered (100nF everywhere) and the line shows ca. 20 mV ripple in operation. The oscillator is decoupled from the VCC line because that causes lots of nasty noise usually. If you wish, I’ll send you the circuit diagram.

The code is the usual:


DEFINE LCD_etc…. ‘Setup LCD

Pause 1000 ‘Settle pause

LCDOUT, $FE, 1, “ Blah blah” ‘Write #1

GOSUB somewhere ‘Fetch, calculate variable

LCDOUT $FE, $C0, “ Blah “, DEC Variable ‘Display variable

I haven't got another unit of this size and type, to take another type for test will involve (sigh) a large amount of work as this is built-in and direct connected. If I don't get it to work, though, I'll buy a new one eventually. I don't like getting beat, though.

One point, I’m using a 16F877 and have the LCD defined to the D-Port as the only port free. I’m wondering if some register needs to be set/reset. I’ve been caught like that before. Is anything known? I’ve not found anything in the PIC Data book, but something with the parallel port control possible?

Greetings,

Rob

[Rhatidbwoy]

I was having a problem with HANTRONIX 20 x4.

I fixed the problem with a pause. In description to what I was getting was that I would get the second line to go and the fourth line to go. Not the first nor the third line to light. I played with many things, but what came to work was that I need a pause.

When you write your first line you normally would not need a clear screen (lcdout $fe, 1). So the second thing would write. leaving nothing for hte first line. This is were the pause is needed. So it looks something like this:

lcdout $fe,1
pause 10 'what ever value. I used 10
lcdout $fe, address (first line), (what ever you want to write here)
lcdout $fe, address (second line), (what ever you want to write here)

This might lead to something good and it might not, but it is something worth your while to try. I tried this with the 20x4 HANTRONIX and I got my screen to do what I wanted it to do.

[boboco]

Hi Rhatidbwoy,

I've tried all sorts of delay times beween lines, nothing works. I've ordered a new display, as I suppose this one to be defect. Thanks anyway.

Greetings

[Acetronics2]

Hi, Boboco

Was it a 50% Discount ???

...

Seriously, you should ask a question about that on the Displaytech site ...

Alain

[Dave]

boboco, As Rhatidbwoy mentioned I have found in the past (8+ years) that most LCD displays require anywhere from 5 to 15 Milliseconds to execute a clear command "$FE,01" or a home command "$FE,02". I have found this to be true with displays from OPTREX,ITRON,and CRYSTALFONTZ. They are all compatable with HD44780 type lcd controllers found on most lcds. Also whenever I use a command to place the cursor to a different location on the lcd I always use "PAUSEUS 100" as I have found in the past some displays require this delay. I have had no problems with any LCD or VFD displays using delays in my software as I have mentioned. LOL

Dave Purola,
N8NTA

[Luciano]

Initialization of a 16x2 LCD.

(4 bit Interface).

The first picture is the initialization of a Hitachi HD44780.
The second picture is the initialization of a Samsung KS0077.

Best regards,

Luciano

Hitachi HD44780 initialization
(The above picture)

E=1  D7=0  D6=0  D5=1  D4=1
E=1  D7=0  D6=0  D5=1  D4=1
E=1  D7=0  D6=0  D5=1  D4=1
E=1  D7=0  D6=0  D5=1  D4=0

E=1  D7=0  D6=0  D5=1  D4=0
E=1  D7=1  D6=0  D5=0  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=1  D6=1  D5=1  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=0  D6=1  D5=1  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=1  D6=1  D5=0  D4=0

Samsung KS0077 initialization 
(The above picture)

E=1  D7=0  D6=0  D5=1  D4=1
E=1  D7=0  D6=0  D5=1  D4=1
E=1  D7=0  D6=0  D5=1  D4=1
E=1  D7=0  D6=0  D5=1  D4=0

E=1  D7=0  D6=0  D5=1  D4=0
E=1  D7=0  D6=1  D5=0  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=1  D6=0  D5=0  D4=1

E=1  D7=0  D6=0  D5=1  D4=0
E=1  D7=0  D6=0  D5=0  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=0  D6=0  D5=0  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=1  D6=1  D5=1  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=0  D6=1  D5=1  D4=0

E=1  D7=0  D6=0  D5=0  D4=0
E=1  D7=1  D6=1  D5=0  D4=0

[boboco]

Hi all,

thanks for the help.

Curious is that the first line functions exactly as it should in every way, only the second line not. If I turn the contrast up to maximal all pixels turn black, though, so at least the line isn't dead.

I've temporarily replaced the Displaytech with another type of unit. (all that work...., sob!) It worked at once so I take it that the Displaytech is bugged in some way. I've ordered a new one and hope that that will work, otherwise I'll have to change the whole construction to use some other. I'll report when I've got the results.

Another short question on LCD control +PBP. If I want to control a 4 liner, which is essentially two complete LCDs in one, I've been doing it by switching both enable lines via resistors from one port and shorting each of the enable lines respectively with another two ports to disable it.

It must be possible to program the PIC so that the selection of two enables is directly possible. (DEFINEs?) I've looked on the board but haven't found anything. Any ideas?

Greetings

Rob

[boboco]

Hi all,

thanks for the help.

Curious is that the first line functions exactly as it should in every way, only the second line not. If I turn the contrast up to maximal all pixels turn black, though, so at least the line isn't dead.

I've temporarily replaced the Displaytech with another type of unit. (all that work...., sob!) It worked at once so I take it that the Displaytech is bugged in some way. I've ordered a new one and hope that that will work, otherwise I'll have to change the whole construction to use some other. I'll report when I've got the results.

Another short question on LCD control +PBP. If I want to control a 4 liner, which is essentially two complete LCDs in one, I've been doing it by switching both enable lines via resistors from one port and shorting each of the enable lines respectively with another two ports to disable it.

It must be possible to program the PIC so that the selection of two enables is directly possible. (DEFINEs?) I've looked on the board but haven't found anything. Any ideas?

Greetings

Rob