optrex 323

a typo in serdisplib versions 1.97.5 - 1.97.7 renders the driver for this display unusable.
this bug has been fixed in version 1.97.8.

optrex 323 is a low-cost graphic display. i bought two displays at Neuhold Elektronik for only less than 15 € / each.

optrex323 showing my logo	output generated by graphlcd (and a 2nd optrex laying in front)
only few electronical parts are needed (7 resistors and 2 voltage regulators)	different view (resistors are underneath the voltage regulator)

when connecting an optrex 323 to the parallel port you don't have to fool around with different wirings because fortunately a 'reference wiring' exists which is used by all projects i know (the document is written in german, i will try to translate the most important parts).

you'll find further examples of projects using an optrex 323 below (links).

signals:

    Signal name  PC            LCD     Signal name
    --------------------------------------------------------------------------------------
    Data 0       2             12      SI   serial data input of LCD
    Data 1       3             11      SCLK serial Clock line of LCD
    Data 2       4              9      D/C  (or sometimes labelled A0) command/data switch
    Data 3       5              8      CS   first high active Chip select input
    Data 4       6              7      /CS  second low active Chip select input
    Data 5       7              6      /RES low active Reset input
    Data 7       9              3           high active Backlight input
    Ground      18              4      Ground for printer port and +9V
    Ground      18             13      Ground for printer port and +5V
                --             10      +5V (0.4 mA) Chip power supply
                --              2      +9V (125 mA) Backlight power supply

    

circuit:

part list:

    Part#   Type                Value        Annotation
    ---------------------------------------------------------------------
    R1-R7   Resistor            1 kOhm       
    IC1     Voltage Regulator   7805         
    IC2     Voltage Regulator   7809         'stronger' version

    

the pixel space of an optrex 323 can be split into three areas:

• double-sized pixels (dark-grey in the picture above, 4 columns (two on each side))
  unusable for normal displaying of images or other generic output
• "standard area" (normal grey, 115x54)
  used by the built-in font-generator, if only this area is used, no translation is needed.
• "usable area" (light-grey, 117x62)
  standard area plus 8 rows and 2 columns surrounding the standard area

to be able to use all 117x62 pixels, each pixel operation has to be translated:

examples:

setPixel(0,0) needs to be translated to column = 117 and row = 54
setPixel(1,4) will be column = 0 and row = 0

pages vs. rows:

another item to take care of: the display is organised in colums and pages: 8 pixel-rows are combined to a so called page.
as only whole bytes can be transferred to the display, a single pixel cannot be changed without knowing its 7 'neighbour' pixels.
so a display buffer was introduced in the library. pixel changes are all done in this buffer and in a separate step only changed pages are transferred (using an optimising algorithm) to the display. the display buffer is also responsible for the translation of 'real' x/y-addresses to corresponding display addresses.

using the third parameter of serdisp_init(), driver specific options and custom wiring can be set.
common information about passing options and customisable wiring can be found in a separate document.

    examples:
    
      serdisp_init(sdcd, "OPTREX323", "WIRING=3;INVERT=YES");
    

  0 .. no delay
  1 .. one call of gettimeofday()
 >1 .. delay at least x nanoseconds