ericsson r520/t65 (i2c-based)

ericsson r520/t65 displays are controlled using an i2c-based on-glass controller (model name unknown).

frontview of an ericsson r520 display	frontview of an ericsson t65 display

pinout for ericsson r520/t65 displays 1 VLCD +10V (lcd power supply, 10V +/-1V (measured)) 2 VLOGIC +2.7V (logic power supply, measured) 3 SDA i2c-SDA 4 GND GND 5 SCLK i2c-SCLK 6 /RES active low reset annotations the model name of the controller is unknown exact voltage ranges are unknown to me. i used a working cell phone to measure them display contrast may be changed by varying VLCD (about +/- 1V)

pages vs. rows:

the display is organised in columns and pages: 4 pixel-rows are combined to a so called page (one pixel requires 2 bit).
as only whole bytes can be transferred to the display, a single pixel cannot be changed without knowing its 3 '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 'page bytes' are transferred (using an optimising algorithm) to the display.

ericsson r520 display showing a test image	ericsson r520 display with output generated by graphlcd
shadow man ( © by redhat) rendered by multidisplay	another image rendered by multidisplay

i2c-displays only require two signal lines, SDA (data) and SCLK (clock).
furthermore ericsson r520/t65 displays have a RESET (/RES) signal line - but this one can be connected to a hardware reset circuit.

i used D0 and D1 to connect the display to the parallel port. if a hardware reset circuit was not used, /RES was connected to D5.

signals:

                      +----------------------------+
                      |         1 2 3 4 5 6        |
                      |         # # # # # #        |
                      +------================------+
                      |                            |
                      |                            |
                      |                            |
                      |          rear view         |
                      |    connector is visible    |
                      |                            |
                      |           ??n/a??          |
                      |                            |
                      |                            |
                      |                            |
                      +----------------------------+


   Signal name  PC            LCD     Signal name
   ----------------------------------------------------------
   Data 0       2              3      SDATA  i2c-SDA
   Data 1       3              5      SCLK   i2c-SCLK
   Data 5       7              6      /RES   active low reset (or via using a hardware reset circuit)
   Ground      18              4      GND    Ground
               --              1      VLCD   +10 V (lcd power supply, some value around 10V)
               --              2      VLOGIC +2.7V (logic power supply, some value around 2.7)


  Source: user "z01" from forum.lcdinfo.com; voltages measured by Wolfgang Astleitner

    

circuit:

with hardware reset circuit:

part list:

    Part#   Type                Value                  Annotation
    ---------------------------------------------------------------------------------------
    R1-R2   Resistor            1 kOhm       
    R3      Resistor            10 kOhm            
    C1      Capacitor           10 uF
    

with software reset:

part list:

    Part#   Type                Value                  Annotation
    ---------------------------------------------------------------------------------------
    R1-R3   Resistor            1 kOhm       
    

remarks:

• V_LOG needs to be about 2.7V
• changing V_LCD influences the contrast
  (possible values from +9V to +11V ==> low to high contrast; best readable when using +10V; all values measured using trial&error)
• default wiring in serdisplib is: DO = SDA, D1 = SCLK, and a hardware reset circuit is used for /RES.

as i2c-displays only need two signal lines, it may be driven using the serial port. also the power can be gained through it (so no extra power supply is needed!)

signals:

                      +----------------------------+
                      |         1 2 3 4 5 6        |
                      |         # # # # # #        |
                      +------================------+
                      |                            |
                      |                            |
                      |                            |
                      |          rear view         |
                      |    connector is visible    |
                      |                            |
                      |           ??n/a??          |
                      |                            |
                      |                            |
                      |                            |
                      +----------------------------+


    Signal name  PC            LCD     Signal name
    ----------------------------------------------------------
    TxD          3              1      VLCD   +10V (lcd power supply)
    TxD          3              2      VLOGIC +2.7V (logic power supply)
    DTR          4              3      SDATA  i2c-SDA
    GND          5              4      GND    Ground 
    RTS          7              5      SCLK   i2c-SCLK
    ---          -              6      /RES   active low reset, controlled using a hardware reset circuit


    

circuit, part list will follow ...

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, "ERICSSONR520", "INVERT=YES");
      serdisp_init(sdcd, "R520", "WIRING=SDA:D6,SCLK:D7");
    

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