Hi Steve,

The characters look random when displayed.

The code uses the 4 bit interface, on port A of the PIC, with 3 port B lines
handling RS, R/W & E.

It reads the busy flag as part of the "LCD command" / "LCD data" before
proceeding with the write to the LCD.

Does the auto-increment of the "cursor" position work when addressing CGRAM
- the code is relying on this. However I also got the same results when I
did a "Set CGRAM address" for each byte (row) sent to the display.

I may try inserting an artificial delay between the LCD initilisation and
the custom character definition just to allow the LCD to settle.

This LCD is not acutally driven by a 44870, but emulates it. It is one of
the RS "Powertip" range, but the interface is identical (as far as i can
see) to the standard Hitachi chip.

Cheers,

Andy



-----Original Message-----
From: Steve Lawther [mailto:SLawther@HUSKY.CO.UK]
Sent: 21 February 2000 10:11
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: Custom LCD Characters


Andy,

The pseudo code looks fine - When you display a user character afterwards,
 is it blank, random, or has it a pattern to it?

Does your code check the busy bit from the display, or wait the maximum
amount of time in-between writes?

Steve Lawther

> -----Original Message-----
> From: Andy Baker [SMTP:AB@DATCON.CO.UK]
> Sent: Monday, February 21, 2000 9:51 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Custom LCD Characters
>
> Hi all,
>
> My current project is a pre-amplifier, where a PIC (16F84) is used to
> control the switching of the inputs, and to display on an LCD what you are
> listening to. This is all working fine.
>
> For an enhancement, I need some underlined characters for the display, so
> set about using the CGRAM feature of the 44870 -style LCD. Trouble is, it
> doesn't work. I don't have code here with me, but the the gist of what I'm
> doing is below. Anything obvious spring to mind as wrong. I'll post code
> tomorrow if I can.
>
> Alternatively, anyone got any working code I can compare mine against to
> spot the bug?
>
> Thanks,
>
> Andy
>
> Immediately after LCD initialisation, This is what I do:
>
> Set CGRam address (instruction 0x40 sent using known working LCD command
> fucntion)
> For Character = 0 to 7
> For Row = 0 to 7
> Lookup (Character , Row) in table to get data byte
> Write data byte to LCD using known working LCD data write function)
> Endfor
> Endfor
>
>
--------------------
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