Have you set the bias voltage?
You should have it at the point where the char cells are JUST starting
to get dark.
Without the bias voltage, even if you have it right, you won't see anything.

Second: Verify the timing, and sequence of events.  Add extra delays.



On 6/10/07, Matthew Mucker <matthew@mucker.net> 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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