AVR-Chat

Your problem sounds a lot like one I had once.  Do you have E and RS 
on the same port as D4-7?  If so, you might want to make sure you're 
not glitching the data lines when you output the control signals.  I 
wound up using a shadow for the port so that the data lines wouldn't 
change. 

Phil

--- In AVR-Chat@yahoogroups.com, John Johnson <johnatl@m...> wrote:
> I've been working on an LCD project for two (3?) days now, and 
still 
> have nothing to show for it. I'm trying to use 4 bit mode. I was 
> originally driving a PCF8754AN using I2C, which was in turn 
connected 
> to the LCD. I gave up on that this morning and switched over to 
driving 
> it directly from PORTB. Still no joy. Used someone else's library, 
> nothing. I've looked at the signals using DigiTrace, and they're 
doing 
> exactly what they're supposed to. Tried another LCD, still nothing. 
The 
> LCD stays blank, although at times I see garbage characters, and 
once a 
> flashing cursor. I've tried code written in WinAVR, and even tried 
> BASCOM, which is my emergency backup language just to see the 
hardware 
> is sound. Nothing.
> 
> My initialization sequence is right out of the 44780 data sheet.
> 
> wait
> 3		// 8 bit mode
> wait
> 3		// 8 bit mode
> wait
> 3		// 8 bit mode
> wait
> 2		// 4 bit mode
> 28		// 4 bit mode, 2 line display
> 08		// display off
> 01		// clear display
> 06		// Entry mode, increment, no shift
> 0C		// Display on, cursor off, blink off
> 02		// return home (added out of desperation)
> 80		// Set DDRAM address to 0 (again, out of desperation)
> 48 'H'	// Sent with RS high, should display an H
> 
> I've also added lots of delays so everything is nice and slow, also 
> didn't help.
> 
> I uploaded the waveforms in the Photos section, under the Waveforms 
> folder.
> I can also upload the DigiTrace file is you need it.
> 
> Thanks for any advice that might save my sanity!
> 
> Regards,
>    JJ