Hello, two comments / questions for you...

I'm not sure if it is the same LCD driver chip, but the one in an LCD 
from Lumex I used on this project:
http://www.celestialaudio.com/MC9S12NE64/index.html
had so many problems in 4-bit mode that I gave up and used it in 8-bit 
mode.  I discuss this a little on the webpage.

So if possible, for starters anyway, can you switch to 8-bit mode to 
eliminate that source of possible error?

Secondly, is there a "dimming voltage" on the LCD you are using?  The 
lumex datasheet spec and schematic were given in an unclear way and 
tripped me up.  So for awhile I was doing everything right but no 
display b/c I had that voltage wrong.

Good luck to you.  I was not happy about the problems I had with this 
LCD as well.

J



Matthew Mucker wrote:
> All,
> 
> I've been debugging this problem for weeks and haven't found where my error
> is, so I'm turning to the list for help. I'm trying to drive a Hitachi 44780
> LCD module in 4-bit mode from a PIC chip.
> 
> I have my PIC 16F628 connected to the LCD module as follows:
> 
> RB4 --> LCD_E
> RB3 --> LCD_RS
> RA0 --> LCD_D4
> RA1 --> LCD_D5
> RA2 --> LCD_D6
> RA3 --> LCD_D7
> 
> I have tested each of these outputs and verified that I can write a logic
> '1' or '0' and get the expected voltage.
> 
> I've used Myke Predko's page (www.myke.com/lcd.htm) as my main reference.
> 
> According to MPLAB SIM, my code is writing the following when the LCD_E line
> is blipped:
> 
> 			LCD
> 			DATA	LCD
> TIME			7654	RS	notes
> 
> 0			0011	0	send 0x03, wait 5msec
> 5.1964		0011	0	send 0x03, wait 160 usec
> 5.5218		0011	0	send 0x03 a third time, wait 160 usec
> 5.8472		0010	0	Enable 4-bit mode (following commands are
> two nybbles)
> 6.0126		0010	0
> 6.1766		1000	0	00101000: 4-bit mode, 2 line display, 5x7
> font
> 6.3248		0000	0
> 6.5068		1000	0	00001000: disp. Off, cursor off, blink off
> 6.6730		0000	0
> 6.8370		0001	0	00000001: clear display, wait
> 12.0356		0000	0
> 12.1996		0110	0	00000110: increment cursor/no shift
> 12.3658		0000	0
> 12.5298		1100	0	00001100: display on, cursor off, blink off
> 12.6968		0000	0	
> 12.8608		0010	0	00000010: home cursor
> 18.0618		0101	1
> 18.2258		0111	1	Letter 'W', first character to be displayed
> 
> The LCD doesn't seem to initialize and for sure my characters aren't being
> displayed. I'm getting quite frustrated with this project. I'm hoping
> someone out there can spot the error of my ways for me and help me get back
> on the straight and narrow.
> 
> Thanks,
> 
> -Matt
> 
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