Re: [Lcd4linux-devel] WG: USB based hd44780 units ...

[Michael R. <re...@eu...>]

Hi Till,

> i have a simple question regarding some of the supported usb devices 
> and their drivers. I am currently building a small and cheap (about 
> $5 easy to obtain standard parts) diy usb interface for the hd44780.

Hey, sounds great! My soldering iron is already warming up :-)

> I am now wondering why drivers for similar devices (e.g. the BWCT and
>  USBLCD) aren't included into the hd44780. Is there any reason these 
> devices are not included as interface drivers for the generic 
> hd44780? This would have the advatage, that all those special case 
> handlers from this driver would be available to the usb devices as 
> well.

Well, you may be right, maybe it would be better to make all HD44780
stuff into one driver. On the other hand, the drv_HD44780.c file looks
already complex enough to me :-)

As the "normal" HD4470 driver uses the parallel port (and/or i2c bus),
there are some other files and libs that have to be linked in (generic
parport support, ppdev, ...). All the USB-to-HD44780 drivers don't need
this stuff, but USB support.

Another reason for not merging the drivers is the fact that some drivers
are maintained by people who own just this specific display and/or
interface. So modifications won't interfere with other drivers.

If you think of our "embedded customers", who don't compile a 'generic
LCD4Linux' with all drivers, but prefer a as-small-as-possible
executable with just one (small) driver included, they would not benefit
from such a 'generic' driver.

So I'd prefer the situation as it is, with every Interface having its
own small and simple driver (as long as the interfaces don't have too
much in common)

> I am thinking of making my interface compatible to the bwct (and 
> perhaps add some more features like e.g. adjustable backlight and one
> or two input buttons).

you're right, the BWCT interface has a very nice protocol: it's very
simple, doesn't have too much own intelligence, but passes through the
features the HD44780 provides.

adjustable backlight would be cool (but take care of power
consumption!), keys would be cool, too (although not supported by
lcd4linux at the moment). If your electronics has some spare outputs (to
connect a LED or something) or inputs, I'd appreciate that, too.

Please keep me up to date with your electronic design, as I'm really
very curious :-)


bye, Michael

-- 
Michael Reinelt <re...@eu...>
http://home.pages.at/reinelt
GPG-Key 0xDF13BA50
ICQ #288386781