lcd4linux-devel

[Lcd4linux-devel] Patch for multiple displays

[Stefan B. <st...@tr...>]

Hi Michael and others,

someone wanted to connect 4 displays at once, but it didn't work.
See here:
http://www.linuxforen.de/forums/showthread.php?t=3D235915

The problem is in drv_HD_goto(int row, int col), file drv_HD44780.c, lin=
e  =

839.
Here is a patch:

-------------------------
     /* handle multiple controllers */
     for (pos =3D 0, controller =3D 0; controller < numControllers;  =

controller++)
     {
         pos +=3D CROWS[controller];
         if (row < pos)
         {
             currController =3D (1 << controller);
             break;
         }
     }

     for (pos =3D 0; pos < controller; pos++)
         row -=3D CROWS[pos];
-------------------------

Greetings, Stefan

Re: [Lcd4linux-devel] Patch for multiple displays

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

Hi Stefan,

> someone wanted to connect 4 displays at once, but it didn't work.
> See here:
> http://www.linuxforen.de/forums/showthread.php?t=235915

Hmmm..... how did you solve the problem that you need 5 control signals 
(4 enable, 1 strobe) but have only 4 (either the four "real" control 
signals or DB4..DB7?

I know that theoretically we could use up to eight control lines (high 
data lines + control lines), but that would require some heavy 
modifications to the parport abstraction layer

> The problem is in drv_HD_goto(int row, int col), file drv_HD44780.c, line  
> 839.
> Here is a patch:

Could you please provide a "real" patch (a context diff)?


TIA, Michael

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

Re: [Lcd4linux-devel] Patch for multiple displays

[Stefan B. <st...@tr...>]

Hi Michael,

here's the patch:
---------------------------
--- drv_HD44780.c       2007-06-05 23:07:08.000000000 +0200
+++ drv_HD44780_new.c   2007-06-05 23:15:24.000000000 +0200
@@ -843,8 +843,9 @@
             currController =3D (1 << controller);
             break;
         }
-       row -=3D CROWS[controller];
      }
+    for (pos =3D 0; pos < controller; pos++)
+       row -=3D CROWS[pos];

      /* column outside of current display's width */
      if (col >=3D CCOLS[controller])

---------------------------

I didn't solve the problem with the control signals, i have to ask why
there are restrictions how they are wired.
For example, he has four displays and wants to set the four enable lines=

to DB4-DB7 and STROBE + RS to the control signals..

Greetings, Stefan



Am 05.06.2007, 22:09 Uhr, schrieb Michael Reinelt <re...@eu...>:

> Hi Stefan,
>
>> someone wanted to connect 4 displays at once, but it didn't work.
>> See here:
>> http://www.linuxforen.de/forums/showthread.php?t=3D235915
>
> Hmmm..... how did you solve the problem that you need 5 control signal=
s  =

> (4 enable, 1 strobe) but have only 4 (either the four "real" control  =

> signals or DB4..DB7?
>
> I know that theoretically we could use up to eight control lines (high=
  =

> data lines + control lines), but that would require some heavy  =

> modifications to the parport abstraction layer
>
>> The problem is in drv_HD_goto(int row, int col), file drv_HD44780.c, =
 =

>> line  839.
>> Here is a patch:
>
> Could you please provide a "real" patch (a context diff)?
>
>
> TIA, Michael
>

Re: [Lcd4linux-devel] Patch for multiple displays

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

Hi Stefan,

> here's the patch:
> ---------------------------
> --- drv_HD44780.c       2007-06-05 23:07:08.000000000 +0200
> +++ drv_HD44780_new.c   2007-06-05 23:15:24.000000000 +0200
> @@ -843,8 +843,9 @@
>             currController = (1 << controller);
>             break;
>         }
> -       row -= CROWS[controller];
>      }
> +    for (pos = 0; pos < controller; pos++)
> +       row -= CROWS[pos];
> 
>      /* column outside of current display's width */
>      if (col >= CCOLS[controller])
> 
> ---------------------------


Are you *really* sure about this? Without trying, just by looking at the 
code, I guess your patch is wrong. You would decrement 'row' two times...

> I didn't solve the problem with the control signals, i have to ask why
> there are restrictions how they are wired.
> For example, he has four displays and wants to set the four enable lines
> to DB4-DB7 and STROBE + RS to the control signals..

The restriction comes from the fact that control and data signals share 
the same bits (signals are 8 bit wide), If I allow them to get mixed, 
I'd have to resize the data type to 16 bit, and declare the lower 8 as 
data lines and the upper 8 as control lines. This would require massive 
rewrite of the parport abstraction layer, and probably a rewrite of all 
parport drivers.


bye, Michael

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