LCD display remains empty

[selbstdual]

I wrote this to display Geez on a lcd and it showed nothing. Can this be due to the code. Circuitry is the one in the manual next to lcdout. PIC 16F628A.

    Define OSC 20
    
Go:    
    LCDOUT "Geez"
    Sleep 100
    GOTO Go

Greetings

[mat janssen]

Whe you read the book that came with your version of picbasic you will see that some declarations must be made for the LCD.
In the declartions the display driver will know how much pins and where the pins come from.
like this:

	        DEFINE	LCD_DREG PORTB
		DEFINE	LCD_DBIT 0
		DEFINE	LCD_RSREG PORTB
		DEFINE 	LCD_RSBIT 4
		DEFINE	LCD_EREG PORTB
		DEFINE	LCD_EBIT 5	
		DEFINE	LCD_BITS 4
		DEFINE	LCD_LINES 2
		DEFINE	LCD_COMMANDUS 2000
		DEFINE	LCD_DATAUS 50

[selbstdual]

I thought this was only necessary if you do not use the standard setup....

I tried and it did not change anything. So.

I got this:

   Define OSC 20
        DEFINE	LCD_DREG PORTB
		DEFINE	LCD_DBIT 0
		DEFINE	LCD_RSREG PORTB
		DEFINE 	LCD_RSBIT 4
		DEFINE	LCD_EREG PORTB
		DEFINE	LCD_EBIT 5	
		DEFINE	LCD_BITS 4
		DEFINE	LCD_LINES 2
		DEFINE	LCD_COMMANDUS 2000
		DEFINE	LCD_DATAUS 50
    
Go:    
    LCDOUT "Geez"
    Sleep 100
    GOTO Go

[mat janssen]

Let us see how you connected everything from the chip to the display.
Try to adjust the background voltage, may be that is the problem!
Put a pause of 1 sec. between the declaration and your programm. Maybe the display was not yet setup.

[selbstdual]

I have not told you yet that the LCD's functionality is not proven. I was given it by someone in a waste utilization for free.

How do I figure out whether it works or not? I was able to make the lcd's points show(two rows, all matrices black). What can I conclude from that?

[Dave]

selbstdual, If you can see all black pixels then it sounds like the contrast is set too high. How do you have the contrast circuit setup? It should be at minimum a 5k pot between VCC and ground with the center wiper connected to the contrast input pin.

Dave Purola,
N8NTA

[selbstdual]

Dave, does seeing the matrices mean that the display is working at all?

[Kamikaze47]

Try adding these 2 things:

   Define OSC 20
        DEFINE	LCD_DREG PORTB
		DEFINE	LCD_DBIT 0
		DEFINE	LCD_RSREG PORTB
		DEFINE 	LCD_RSBIT 4
		DEFINE	LCD_EREG PORTB
		DEFINE	LCD_EBIT 5	
		DEFINE	LCD_BITS 4
		DEFINE	LCD_LINES 2
		DEFINE	LCD_COMMANDUS 2000
		DEFINE	LCD_DATAUS 50

                PAUSE 100
    
Go:    
    LCDOUT $FE,1,$FE,2,"Geez"
    Sleep 100
    GOTO Go

[selbstdual]

First of all I want to make sure that the lcd is working at all. How do I do that?

[Kamikaze47]

first, make sure that when you apply power, the top line of the LCD displays solid blocks. If this is the case, try the additions i suggested above.

If this is not the case, you probably need to have a contrast control for the LCD. You need a variable resistor and hook it up like this:

LCD pin 3
   |
   |   +5v
   |    |
   |    |
   |    \
   |    /
   ---->\ variable resistor (10k or bigger)
        /
        \
        |
        |
       gnd

[bbazor]

I am not sure if this is your problem, but you might want to try changing "Define OSC 20" to all capitals "DEEFINE OSC 20". The compiler may not recognize lower case in DEFINE statements.

Ben

[selbstdual]

Can we come back to the topic whether the display works or not? Actually the blocks are black, when power is applied. But does that mean that symbols can be displayed? How to figure that out?

[Archangel]

I wrote this to display Geez on a lcd and it showed nothing. Can this be due to the code. Circuitry is the one in the manual next to lcdout. PIC 16F628A.

    Define OSC 20
    
Go:    
    LCDOUT "Geez"
    <font color=red>Sleep 100</font color>
    GOTO Go

Greetings

Try changing sleep 100 to pause 100 or even pause 1000
JS

[Kamikaze47]

Can we come back to the topic whether the display works or not? Actually the blocks are black, when power is applied. But does that mean that symbols can be displayed? How to figure that out?

Did you read my last post?

When power is applied, does the entire screen show blocks, or just the top line? There is a big difference.