OLED Display Noise problem

[gunayburak]

I tried adding pause 100 command right after the lcdout commands but the noise only got lowered just a little .. This is definitely not normal .. But when I apply 1000 ms of delay it almost stops making noise on the screen(there is still a little) ... But It musn't be that bad .. It is an oled and the datasheet claims parameters for write/read around nanosecs .. Where do I do the mistake ? , May it have anything to do with the LCD or a defective circuit component ... On the other hand I think It musn't have because It can display chars succesfully with a huge amount of delay periods ...

[pedja089]

That sound to me as bad PCB design and/or power supply. But sill could be bad LCD driver.
If long delays make artifact disappear, then capacitive coupling between LCD signals and power lines can cause that.
You can try test that. Add pull down resistor 1K to LCD Enable pin, and create easy way to disconnect LCD and resistor from PIC, as close as possible to LCD.

pause 500
                        
lcdout $FE,$28
lcdout $FE,$17
lcdout $FE,$06
lcdout $FE,$08
lcdout $FE,$01
lcdout $FE,$02
lcdout $FE,$0C

lcdout $FE,$80,"BU BiR DENEMEDiR"
LCDOUT $FE,$C0,"  iKiNCi SATIR  "
PAUSE 10000' Disconnect only LCD enable pin before pause timeout
Main:
lcdout $FE,$80,"BU BiR DENEMEDiR"
LCDOUT $FE,$C0,"  iKiNCi SATIR  "
GOTO Main

Display shouldn't update any more. If you see dots then 99% problem is with PCB layout, and decoupling.
If there is no dots on LCD then problem is with LCD.

[gunayburak]

That sound to me as bad PCB design and/or power supply. But sill could be bad LCD driver.
If long delays make artifact disappear, then capacitive coupling between LCD signals and power lines can cause that.
You can try test that. Add pull down resistor 1K to LCD Enable pin, and create easy way to disconnect LCD and resistor from PIC, as close as possible to LCD.

pause 500
                        
lcdout $FE,$28
lcdout $FE,$17
lcdout $FE,$06
lcdout $FE,$08
lcdout $FE,$01
lcdout $FE,$02
lcdout $FE,$0C

lcdout $FE,$80,"BU BiR DENEMEDiR"
LCDOUT $FE,$C0,"  iKiNCi SATIR  "
PAUSE 10000' Disconnect only LCD enable pin before pause timeout
Main:
lcdout $FE,$80,"BU BiR DENEMEDiR"
LCDOUT $FE,$C0,"  iKiNCi SATIR  "
GOTO Main

Display shouldn't update any more. If you see dots then 99% problem is with PCB layout, and decoupling.
If there is no dots on LCD then problem is with LCD.

Well ;

I did exactly as you asked me to do and as you say it's got to do with the lcd then ...

[Scampy]

Well ;

I did exactly as you asked me to do and as you say it's got to do with the lcd then ...

I don't have the same chip, but used an 18F4580 with a 2 x 16 LCD and just changed the lines to run the LCD from port B to suit the EasyPIC5 development board and I don't get any strange random pixels and I'm running the chip at 20Mhz so the switching is much faster, so it would suggest that it is your hardware that is at fault.

ASM 
  __CONFIG    _CONFIG1H, _OSC_HS_1H
  __CONFIG    _CONFIG2L, _PWRT_ON_2L  
  __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
  __CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H  
  __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ENDASM


DEFINE  OSC 20    

DEFINE LCD_DREG  PORTB                  ' LCD Data port
DEFINE LCD_DBIT  0                      ' starting Data bit (0 or 4)
DEFINE LCD_EREG  PORTB                  ' LCD Enable port
DEFINE LCD_EBIT  5                      '     Enable bit  (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTB                  ' LCD Register Select port
DEFINE LCD_RSBIT 4                      '     Register Select bit   (on EasyPIC 5 LCD)
DEFINE LCD_BITS  4                      ' LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 4                      ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000               ' Command delay time in us 
DEFINE LCD_DATAUS 50                    ' Data delay time in us 

'-------------------------------------------------------------------------------
PORTA=%00000000     :      PORTB=%00000000
TRISA=%00000000     :      TRISB=%00000000 
'ADCON0=%00000001    :      ADCON1=%10110000
'ANSELA=%00000       :      ANSELB=%00000000
'OPTION_REG.7=0     
'-------------------------------------------------------------------------------                                 


pause 500
                        
lcdout $FE,$28
lcdout $FE,$17
lcdout $FE,$06
lcdout $FE,$08
lcdout $FE,$01
lcdout $FE,$02
lcdout $FE,$0C
 
MAIN:
              
lcdout $FE,$80,"BU BiR DENEMEDiR"
LCDOUT $FE,$C0,"  iKiNCi SATIR  "

goto main

Replaced the 20Mhz with a 4Mhz xtal and recoded and the display was fine.

[gunayburak]

I don't have the same chip, but used an 18F4580 with a 2 x 16 LCD and just changed the lines to run the LCD from port B to suit the EasyPIC5 development board and I don't get any strange random pixels and I'm running the chip at 20Mhz so the switching is much faster, so it would suggest that it is your hardware that is at fault.

ASM 
  __CONFIG    _CONFIG1H, _OSC_HS_1H
  __CONFIG    _CONFIG2L, _PWRT_ON_2L  
  __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
  __CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H  
  __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ENDASM


DEFINE  OSC 20    

DEFINE LCD_DREG  PORTB                  ' LCD Data port
DEFINE LCD_DBIT  0                      ' starting Data bit (0 or 4)
DEFINE LCD_EREG  PORTB                  ' LCD Enable port
DEFINE LCD_EBIT  5                      '     Enable bit  (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTB                  ' LCD Register Select port
DEFINE LCD_RSBIT 4                      '     Register Select bit   (on EasyPIC 5 LCD)
DEFINE LCD_BITS  4                      ' LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 4                      ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000               ' Command delay time in us 
DEFINE LCD_DATAUS 50                    ' Data delay time in us 

'-------------------------------------------------------------------------------
PORTA=000000     :      PORTB=000000
TRISA=000000     :      TRISB=000000 
'ADCON0=000001    :      ADCON1=110000
'ANSELA=000       :      ANSELB=000000
'OPTION_REG.7=0     
'-------------------------------------------------------------------------------                                 


pause 500
                        
lcdout $FE,$28
lcdout $FE,$17
lcdout $FE,$06
lcdout $FE,$08
lcdout $FE,$01
lcdout $FE,$02
lcdout $FE,$0C
 
MAIN:
              
lcdout $FE,$80,"BU BiR DENEMEDiR"
LCDOUT $FE,$C0,"  iKiNCi SATIR  "

goto main

Replaced the 20Mhz with a 4Mhz xtal and recoded and the display was fine.

What can I say .. I am so unlucky with these OLEDs .. But thanks for your effort anyway ..

[gunayburak]

Today a new EA OLED display has arrived yet the same problem still occurs ... There might be a picbasic incompatibility with the lcd because my connections are exactly the same with the code I shared , nothing more nothing less ..

[Scampy]

Looking at the data sheet, by default it's in 4/8 bit mode so should work the same way as a normal 2 x 16 LCD display. The only suggestion to prove if the OLED is part of a faulty batch would be to run the code above on a different PIC (18F4580 or the good old 16F877A) - If that works then the problem would appear to be with the original pic, if the OLED still gives odd pixels then its the display and I would send them back for a refund and order from a different supplier