Re: [Lcd4linux-devel] display on WRAP-Board - how fast is i2c? ho w good is the lpc connector?

[Luis.F.Correia <Lui...@se...>]

Hi Stefan! 

> -----Original Message-----
> From: Stefan Krister [mailto:ste...@cr...] 
> 
> Hi,
> 
> I wish to connect a lcd to my WRAP-Board. I'm currently 
> examining on what connector the best results there will be.
> 
> I2C - the last I read here was "and beware! we are planning 
> new and unlikely features to this interface (yes, we are also 
> adding the kitchen sink)" - one year ago. What happened 
> meanwhile? Are there any circuit diagrams available?

Nothing much has happened since that statement, as both me and
Paul have been busy with some other stuff.

I2C is usable, but need some tweaking in the driver as the AccessBus
controllers are not in any of the default IOport locations.

(i can point you to this modified driver location if needed)

Then, a simple I2C 8 bit I/O extender is needed, we have successfully
used the PCF8574.

No 3.3-5v level adapter are needed as the PCF can be driver exclusively
at 3.3v, while the outputs to the LCD display fall within the TTL levels.

This affirmation was done my heart, as I don't have the breadboard 
assembly with me right now. But can confirm later on today.

The hardware is very simple, with support for a 4bit HD44780, which is
also the only type of display controller that is supported under the I2C
interface.

Of course other display controllers could be supported, provided that 
someone writes the driver code :P


> USB - I read about the thing, Till Harbaum developed, but I 
> think, it's too complicatet. The WRAP-USB is also limited to 
> 100mA - no way to drive a LCD and the interface.

The +5v line in the WRAP board is almost unuseable, speccially if you use
a miniPCI card that draws some power from it.

A 7805 can be added to the board (some tricky soldering involved) or the 
board can be converted to work from +5V directly (no PoE possible).

Only with these two options you can consider to use the USB interface.

> I prefer - until now - using the "J2" - LPC-Expansion on my 
> WRAP-Board.
> There are enough GPIO-Pins and a 3.3V power supply. Is 
> lcd4linux already  able to support this way?

I also had some thoughts on using the GPIO pins, but found it way too tricky
to be done correclty (at least from me).


> But that would not be enough for me .-))
> 
> I want also to have a RGB-backlight. Take a look at 
> http://www.lcd-module.de/eng/dog/dog.htm - theese "display on glas"
> modules are running with 3.3V, there are many colors and 
> backlight-colors available and - a RGB-backlight.
> 
> I think, the power consumption is o.k. for the WRAP-connector.
> 
> So, how to interface with that beast? I will use 2 shift registers
> (74HC595) what gives me 16 lines - D0 ... D7, E, RW, and RS. 
> The remaining 5 lines will be good for colorizing the 
> backlight in 32 different colors.
> 
> >From my WRAP I will make use of 4 GPIO lines. 2 for the input of the
> shift registers, 1 for both clock inputs and 1 for the latch.
> 
> So, how far is that possible with lcd4linux? I couldn't took 
> a look into the lcd4linux-source - it seems the server is 
> down for the last few days ... if anybody please could mail 
> me - thanks.
> 

Everything is possible to do with Lcd4Linux... provided that you write 
some code :)



Luis Correia   
Bering uClibc Team Member

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