AW: [Lcd4linux-devel] USB based hd44780 units ...

[<li...@ha...>]

Hi,

 --- Urspr=FCngliche Nachricht --- 
Datum: 20.01.2006 16:43
Von: Paul Kamphuis <pau...@xs...>
> Till, I really like the idea of a $5 DIY USB interface for a HD44780. 
> What are you planning on using?
There's a nice project to do software bit-banging usb with atmel avrs
(http://www.obdev.at/products/avrusb/index.html). I flashed the sensor 
example code onto one of my atmega8 demo boards and it was immediately
recognized by my pc. It should be quite simple to add 4 bit lcd interface
to this. The firmware doesn't need to know much about the display, since
the bwct driver sends the hd44780 commands via usb. I'll only have to do 
some small tests to e.g. prevent the pc from switching the display into
8bit mode. Other than that i can just forward any command directly to the
display. I am planning to allow for two controllers and make contrast and
backlighting configurable via usb. Only few parts will be needed besides 
the avr itself. Even the 40mA for the backlight leds may be driven
directly 
by the avr. The whole device is meant to be open source/open hardware, so
you can start heating up the soldering irons ...

The whole device will not be 100% usb compliant. The soft-usb
implementation
does not allow for all the necessary crc checks and the like and the
final
device will not meet the usb spec regarding power consumption etc. But it
should work good enough for most applications.

I do understand, that the other usb adaptors are sold with few different 
display types only. But i'd like to use as much different display as the
generic hd44780 driver does. I am still not convinced, that having a
seperate
usb driver doing much of the same things the generic driver does (e.g. 
adopting the addressing scheme for 16 col displays) is a clever thing ...

Ciao,
  Till