Re: [Lcd4linux-devel] Driver for "Bit-mapped" displays

[Ernst B. <e.b...@xe...>]

On Tuesday 01 August 2006 23:04, Michael Reinelt wrote:
> Hi there,
>
> >>> Since such displays don't fit the drv_generic_text and
> >>> drv_generic_graphic models well (There is no concept like rows/cols or
> >>> pixels), I'll probably have to code the driver from scratch.
>
> Well, maybe. But try to keep as close as possible on the "generic text"
> side, as lots of widgets depend upon it.

Well, sure.

> > struct WIDGET_GPO only has "int num", I could abuse that to contain the
> > bit location (like num = (byte_location << 3) | bit_location)
>
> You can define one single symbol as a GPO, but you can group them, too.
> Just as you like.

Ah, that was the missing bit... I somehow had the impression they were 
single-bit. So unless I implement different brightness levels/greyscales per 
segment, GPOs should do the trick.

> >>>  - drv_generic_bitmapped: Provides a "framebuffer", where each bit is
> >>> linked to a segment on the display and helper routines
>
> Please don't do that yet. Write a driver, do it the "ugly" way, wait for
> the next display that fits into this area, try to find commonalities,
> and then think about a "generic" part.

hmm, I probably could base the driver on generic_text and generic_gpio, add 
some "translation" layer in the driver mapping the different text areas on 
different virtual rows. No new widgets or changes to layout.c needed here, 
but probably hard to adapt to different displays.
>
> This stuff is difficult: I've got a fisplay here that shares a part of
> graphic area (about 100x8 pixels) with lots of symbols and a 7-digit
> area. Where would that one fit into? I've no idea....

Heh. 100x8 Pixels would fit into 25 GPOs. (just kidding)

...
>
> Hmmm... you can render all alphanumeric into 7-digit, too, by mixing
> upper and lowercase.

Well, I know... my very first computer had eight 7segment chars as only 
display...

> As I said above, don't try to generalize at this time.
>
> >>>  - a specialization of the "Bar" class, for those nifty equalizer bars
> >>> found on my display
>
> That could be a GPO, too. GPO's are 32 bit at the moment, so if your
> bars exceed 32 leds....

Yep, some sort of "percent value" => "bit pattern" translation would be 
missing, but could be quite easily added as evaluator plugin.

> There may be a "TrueType" Widget for graphic displays in the future (any
> volunteers? :-)

Well, sorry. I'll pass... Though there are quite some 7Segment Truetype fonts 
out there *g*.

> bye, Michael (looking forward to see your cool display working with
> lcd4linux!)

Well, looking forward myself, having it sit arround in a box half done for 
quite a while now ;)

BTW, in case someone wants to play in the same sandbox, the display I used is 
still sold by Pollin (www.pollin.de) for 75 cent (50cent if you order three). 
They also have some example schematic for it (bit banging iface on parport, 
with some pascal software)

/Ernst