[Lcd4linux-devel] WRAP platform and LCD4Linux

[Luis C. <lfc...@lf...>]

Hi!

as most of you know, i'm half of the team that brought a largely 
undocumented I2C-HD44780 driver to LCD4Linux (l4l).

Until now, my experiments were less then satisfactory, but up to some 
extent, I could honestly say that l4l did in fact work with the I2C driver.

With the 2.4 series kernel, a lot of tweaking was needed in order to 
make the special AccessBus driver to compile and load properly.

For the newer kernels, things were a lot easier, and there was a 
scx200_acb driver which seems to work perfectly ok with it (i haven't 
tested it myself).

But still, the results were less then perfect.

This was all fine until Till Harbaum released his LCD2USB.

After having assembled the components in the PCB (while almost frying an 
LCD module), I was absolutely amazed of how well it is working with the 
same WRAP board. The same lcd4linux.conf file produced such an 
incredible different results, with this new interface!!! Light years faster!

This performance comes with a price... a 6% price to be accurate.
While my I2C approach takes about 0.0% of CPU time (analysed with top), 
the USB variant eats something from 5 to 6.4% of CPU time.

This doesn't seem much for a server, but it is a lot to a 266Mhz router.


Conclusions (this is getting toooo looooooong):

I will probable just write a WIKI page describing the I2C LCD interface. 
The code is probably not going to get much more additions, no 8bit 
interface, no other fancy stuff.

I do however strongly recommend the LCD2USB interface for those that 
still want to invest some time with WRAP. (no Stefan, don't waste 
anytime reprogramming the GPIO pins, it's worthless)

It costs a bit extra, as I recomment that you buy the USB extension 
board (it has some ESD protection for the CPU) and buy (or build) the 
LCD2USB circuit from Till Harbaum.


Be good to each other, be happy!

Luis Correia
Bering uClibc team member,
LCD4Linux developer

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