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GraphLCD driver library

The GU256X64-3900 driver
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Description
-----------
The GU256X64-3900 driver supports Noritake GU256X64-3900 VFD displays.
The VFD is either operating in 8 bit-mode connected to a single PC
parallel port or in serial mode connected to a single PC serial port.


Wirings
-------
The GU256X64-3900 driver supports the following connections on a
parallel port:
 - Standard
 - Satyr

Standard wiring:

  printerport   LCD          other
  -----------   ----------   ----------
  D0     (02)   DB0   (08)                (DataBit 0)
  D1     (03)   DB1   (07)                (DataBit 1)
  D2     (04)   DB2   (06)                (DataBit 2)
  D3     (05)   DB3   (05)                (DataBit 3)
  D4     (06)   DB4   (04)                (DataBit 4)
  D5     (07)   DB5   (03)                (DataBit 5)
  D6     (08)   DB6   (02)                (DataBit 6)
  D7     (09)   DB7   (01)                (DataBit 7)
  ACK    (10)   RDY   (12)                (Display Ready)
  INIT   (16)   nWR   (10)                (Write)
  GND    (18)   GND   (09)   GND          (Ground)
  GND    (19)   GND   (11)   GND          (Ground)
  GND    (20)   GND   (13)   GND          (Ground)
  GND    (21)   GND   (14)   GND          (Ground)
                VCC   (15)   VCC          (Power supply 5V)
                VCC   (16)   VCC          (Power supply 5V)

Satyr Wiring:

  printerport   LCD          other
  -----------   ----------   ----------
  nSTRB  (01)   nWR   (10)                (Write)
  D0     (02)   DB0   (08)                (DataBit 0)
  D1     (03)   DB1   (07)                (DataBit 1)
  D2     (04)   DB2   (06)                (DataBit 2)
  D3     (05)   DB3   (05)                (DataBit 3)
  D4     (06)   DB4   (04)                (DataBit 4)
  D5     (07)   DB5   (03)                (DataBit 5)
  D6     (08)   DB6   (02)                (DataBit 6)
  D7     (09)   DB7   (01)                (DataBit 7)
  BUSY   (11)   RDY   (12)                (Display Ready)
  GND    (18)   GND   (09)   GND          (Ground)
  GND    (19)   GND   (11)   GND          (Ground)
  GND    (20)   GND   (13)   GND          (Ground)
  GND    (21)   GND   (14)   GND          (Ground)
                VCC   (15)   VCC          (Power supply 5V)
                VCC   (16)   VCC          (Power supply 5V)

Note: The pin numbering may vary with other displays.


The GU256X64-3900 driver supports the following connection on a
serial port:

  serialport   LCD          other
  ----------   ----------   ----------
  DCD   (01)   DTR   (02)
  RxD   (02)   TxD   (04)
  TxD   (03)   RxD   (01)
  DTR   (04)   DSR   (03)
  GND   (05)   GND   (07)   GND          (Ground)
  DSR   (06)   DTR   (02)
               VCC   (06)   VCC          (Power supply 5V)

Note: The pin numbering may vary with other displays.

On display switches:
 SW No.   Function                 Default
 ------   --------                 -------
   1      Display address select   Off
   2      Display address select   Off
   3      Display address select   Off
   4      Display address select   Off
   5      Baud rate select         Off
   6      Command mode select      Off      switch DMA On/Off
   7      Operating mode select    Off
   8      Protocol Select          Off

Serial access to GU256X64C-3xx0 is nearly as fast as normal parallel
access but doesn't create the high system load of the parallel
approach. So for me serial access is preferred over normal parallel
mode. Even better is the DMA parallel mode. For DMA mode you have to
switch SW6 on the display to ON.


Configuration Parameters
------------------------
The GU256X64-3900 driver supports the following parameters in config
file:

Device
 Instead of using the direct output via port address (see Port), you
 can use the parport device (/dev/parportX). The advantage over the
 direct output via port address is that this works for non-root users
 also. But it's a little bit slower. The modules ppdev.o, parport.o
 and parport_pc.o must be loaded or compiled into the kernel.

Port
 Sets the port address of the parallel port. If this parameter is not
 given, 0x378 is used. To use this direct output, the program that
 uses the driver library has to be started with user 'root'.

Width
 Sets the horizontal size of the display. If this parameter is not
 given, a default value of 256 pixels is used.

Height
 Sets the vertical size of the display. If this parameter is not
 given, a default value of 64 pixels is used.

UpsideDown
 Rotates the display output by 180 degrees. This might be useful, if
 the LCD is mounted upside-down.
 Possible values: 'yes', 'no'
 Default value: 'no'

Invert
 Inverts the display.
 Possible values: 'yes', 'no'
 Default value: 'no'

Brightness
 Sets the brightness of your display's backlight.
 Possible values: 0 <= x <= 100)
 Default value: 100

AdjustTiming
 To get a timing that is as accurate as possible, the drivers measure
 the time for port commands (see: benchmark in syslog). You might
 decrease or increase the time to wait after port commands with this
 parameter. Normally, there is no need to change this parameter.
 Possible values: -50 <= x <= 50
 Default value: 0

RefreshDisplay
 Normally, most of the drivers do not update the whole display, but
 only the areas that have changed since last update. So it might be,
 that some faulty pixels would stay a longer time. To avoid this, the
 plugin makes a complete refresh from time to time. This parameter
 defines how often a complete refresh will be done.
 e.g.: A value of 5 means, that the plugin will make a complete
       refresh on every 5th update.
 A value of 0 completely disables complete refreshs. 
 Possible values: 0 <= x <= 50
 Default value: 5

Wiring
 Select the type of wiring your display is connected with.
 Possible values: 'Standard', 'Satyr'
 Default value: 'Standard'

Interface
 Select the interface your display is connnected to.
 Possible values: 'Parallel', 'Serial'
 Default value: 'Parallel'

DMA
 Enables/disables the usage of the controller's DMA mode which
 increases writing speed. This only works in parallel interface mode.
 Possible values: 'yes', 'no'
 Default value: 'yes'