LCD -- melabs sample program

[richard]

ever heard of default settings ?

from the book

PBP assumes the LCD is connected to specific pins unless told otherwise using DEFINEs. It assumes the LCD will be used with a 4-bit bus with data lines DB4 - DB7 connected to PIC MCU PORTA.0 - PORTA.3, Register Select to PORTA.4 and Enable to PORTB.3.

have you set port a to be digital ?

[Michael]

As I said, never picked up an LCD display in my life so yes, knowing the backlight pins beforehand would have been nice. Who's to say the backlight wasn't powered through the Vdd and Vss? If you're new to something, best to spell it all out, right?

My bad on not considering the code within the command LCDOUT and A4 and B3 being part of it's instruction set.

It would have been nice to see that in larger print or part of the example. We all are newbies at one point with everything so no need to -- well, you know.

Thanks kindly for the reply. It must be the fact I'm using a 16c72 but like I say, ADCON1 = 7 sets all pins to digital and it has Ports A & B as most PICs do.

Everything compiles fine also -- I'll get there. Spent too much time on it yesterday.

[Michael]

I'll have to look at ADCON1 -- maybe it doesn't influence Port A -- who knows.

[mark_s]

I hope you know the pic16"C"72 is a one time programmable pic vs. pic16"F"72. So you only get one shot to make it work. Also a common beginner's LCD problem is the contrast control.

[Michael]

contrast is fine.

I have a few thousand 16c72.

just a beginner with LCDOUT. It's using default ports is something you don't think of.

[Michael]

Ok, I give up. Hours spent on this. Maybe someone could be so kind as to look at the code and see why this doesn't function. Something simple perhaps. I realize the 16C72 is an antiquated part but I have a ton of them. I even used another LCD (yes hd44780's) -- even tried another xtal etc. Mclr is high to Vdd, ADCON1 is making pins digital. Changed the defaults because A4 isn't TTL on the 16C72 so used B7 and C7 for RS and E to avoid conflicts -- even did a TRIS on all the pins. Power supply is fine -- this is crazy.

DEFINE OSC 4 '16C72
ADCON1 = 7
TRISA = %00000000
TRISB = %00000000
TRISC = %00000000

DEFINE LCD_DREG PORTA
DEFINE LCD_DBIT 0 'a0 thru a3
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 7
DEFINE LCD_EREG PORTC
DEFINE LCD_EBIT 7
DEFINE LCD_BITS 4
DEFINE LCD_LINES 2

Pause 1000 ' Wait for LCD to startup

mainloop:
Lcdout $fe, 1 ' Clear LCD screen
Lcdout "Hello" ' Display Hello
Pause 500 ' Wait .5 second

Lcdout $fe, 1 ' Clear LCD screen
Lcdout "World"
Pause 500 ' Wait .5 second

Goto mainloop ' Do it forever

End

[Michael]

and for what it's worth all I get are a group of 16 squares on the 2nd line

[richard]

do you have the unused data pins 4 to 7 tied to gnd along with the r/w pin ?