[lcdproc] 4x40 LCD and parallel port

[Jon]

On Thu, 30 Sep 1999, Scott Scriven wrote:

> I think the existing HD44780 code uses the 4-bit interface.
> (?) It might be a good starting point for what you're doing,
> though.  All you need to do is implement a few functions for an
> LCDd driver; the hard part is probably figuring out how to talk
> to the LCD properly.
> 
> There's a mini-howto for writing LCDd drivers in the
> distribution, in  server/drivers/drv_base.h .  I can help if
> you like.  But as for communicating through the parallel port,
> I'm pretty clueless.



a 4x40 driver would probably be easier to write seperatly from the
existing driver, as each has different wiring needs.

A 4x40 lcd pretends that its two 2x40 lcds
the top 2 lines being lcd1 and bottom two being lcd2

On a regular LCD, theres a select line used to tell the lcd when your
talking to it..  on the 4x40, there are two select lines.. one for each
lcd half.

so it would require another dataline (the existing driver only uses 7
bits, 4 for data, 3 for control) and there is one last line free on the
parallel port for data.


most people tend to not want to use a parallel ports control lines, as
they differ depending on the hardware (some cards/ports may not implament
All the control lines, so your work may not be portable.)  however they
all support the 8 databits atleast.


the best way to think of it
imagine having two 2x40 lcds, one on top of the other

the driver will need to know this, and pretend theres a 4x40 area, and
depending where text should be, write to the correct lcd.

i too have one of these lcds and would love to see support for it, but im
not profecent in C (or spelling as you can tell) to create a new driver..




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