OLED Display Noise problem

**gunayburak** · - 29th May 2016, 13:18

Originally Posted by 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.

Code:

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** · - 29th May 2016, 13:50

Originally Posted by gunayburak

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.

Code:

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** · - 29th May 2016, 14:03

Originally Posted by Scampy

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.

Code:

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** · - 4th June 2016, 10:53

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** · - 5th June 2016, 09:22

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

**tumbleweed** · - 5th June 2016, 14:14

Usually issues with junk appearing in the display have to do with not allowing the LCD time to process commands.
If you want to hammer the display as fast as possible then you might try reading the BUSY status flag between operations.

Try this and see if it gets any better (untested, so beware)...

Code:

'-------------------------------------------------------------------------------
define OSC 4
OSCCON=%01101010    'OSC is @ 4 MHZ

'------------- LCD DEFINES ------------------------
DEFINE LCD_DREG PORTB   'LCD data port 
DEFINE LCD_DBIT 4       'LCD data starting bit 0 or 4 

DEFINE LCD_RSREG PORTA  'LCD register select port 
DEFINE LCD_RSBIT 7      'LCD register select bit

DEFINE LCD_RWREG PORTA  'LCD read/write port
DEFINE LCD_RWBIT 0      'LCD read/write pin bit  

DEFINE LCD_EREG PORTA   'LCD enable port 
DEFINE LCD_EBIT 6       'LCD enable bit

DEFINE LCD_BITS 4       'LCD bus size 4 or 8 
DEFINE LCD_LINES 2      'Number lines on LCD

DEFINE LCD_COMMANDUS 6200   'command delay time (in us) - clear display requires 6.2ms
DEFINE LCD_DATAUS 50        'data delay time (in us)

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

pause 500           'wait for display powerup
                        
lcdout $FE,$28      'function set 4-bit mode
call lcd_busy_wait
lcdout $FE,$08      'display off
call lcd_busy_wait
lcdout $FE,$06      'entry mode set
call lcd_busy_wait
lcdout $FE,$17      'char mode + internal power
call lcd_busy_wait
lcdout $FE,$01      'clear display (requires long delay)
call lcd_busy_wait
lcdout $FE,$02      'home
call lcd_busy_wait
lcdout $FE,$0C      'display on
 
MAIN:
    call lcd_busy_wait
    lcdout $FE,$80,"BU BiR DENEMEDiR"
    call lcd_busy_wait
    lcdout $FE,$C0,"  iKiNCi SATIR  "
goto main

'sub lcd_busy_wait
'read lcd busy flag until busy=0
WAITST CON 1        ' delay 1us
busy var bit
lcd_busy_wait:
    busy = 1
    TRISB = TRISB or $F0        'set PORTB D4-D7 to inputs
    @ bcf LCD_RSREG, LCD_RSBIT  'RS=0
    @ bsf LCD_RWREG, LCD_RWBIT  'RW=1
    pauseus WAITST

    'wait for lcd busy flag (D7) to be low
    do while (busy = 1)
        @ bsf LCD_EREG, LCD_EBIT    'EN=1
        pauseus WAITST
        busy = PORTB.7              'read busy bit (bit 7 in upper nibble)
        @ bcf LCD_EREG, LCD_EBIT    'EN=0
        pauseus WAITST
        ' dummy read of lower nibble
        @ bsf LCD_EREG, LCD_EBIT    'EN=1
        pauseus WAITST
        @ bcf LCD_EREG, LCD_EBIT    'EN=0
        pauseus WAITST
    loop

    TRISB = TRISB and not $F0       'set PORTB D4-D7 back to outputs
    @ bcf LCD_RWREG, LCD_RWBIT      'RW=0
 return

You might find that you need to split the cursor position commands and data...

Code:

    call lcd_busy_wait
    lcdout $FE,$80        'move cursor
    call lcd_busy_wait
    lcdout "BU BiR DENEMEDiR"   'send data

Even with doing things like this some displays just don't like being continuously written to and you need to use delays.
Reading the BUSY flag really needs to be done for each byte transferred, so it may not help much at all.

**gunayburak** · - 12th June 2016, 08:15

Originally Posted by tumbleweed

Usually issues with junk appearing in the display have to do with not allowing the LCD time to process commands.
If you want to hammer the display as fast as possible then you might try reading the BUSY status flag between operations.

Try this and see if it gets any better (untested, so beware)...

Code:

'-------------------------------------------------------------------------------
define OSC 4
OSCCON=%01101010    'OSC is @ 4 MHZ

'------------- LCD DEFINES ------------------------
DEFINE LCD_DREG PORTB   'LCD data port 
DEFINE LCD_DBIT 4       'LCD data starting bit 0 or 4 

DEFINE LCD_RSREG PORTA  'LCD register select port 
DEFINE LCD_RSBIT 7      'LCD register select bit

DEFINE LCD_RWREG PORTA  'LCD read/write port
DEFINE LCD_RWBIT 0      'LCD read/write pin bit  

DEFINE LCD_EREG PORTA   'LCD enable port 
DEFINE LCD_EBIT 6       'LCD enable bit

DEFINE LCD_BITS 4       'LCD bus size 4 or 8 
DEFINE LCD_LINES 2      'Number lines on LCD

DEFINE LCD_COMMANDUS 6200   'command delay time (in us) - clear display requires 6.2ms
DEFINE LCD_DATAUS 50        'data delay time (in us)

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

pause 500           'wait for display powerup
                        
lcdout $FE,$28      'function set 4-bit mode
call lcd_busy_wait
lcdout $FE,$08      'display off
call lcd_busy_wait
lcdout $FE,$06      'entry mode set
call lcd_busy_wait
lcdout $FE,$17      'char mode + internal power
call lcd_busy_wait
lcdout $FE,$01      'clear display (requires long delay)
call lcd_busy_wait
lcdout $FE,$02      'home
call lcd_busy_wait
lcdout $FE,$0C      'display on
 
MAIN:
    call lcd_busy_wait
    lcdout $FE,$80,"BU BiR DENEMEDiR"
    call lcd_busy_wait
    lcdout $FE,$C0,"  iKiNCi SATIR  "
goto main

'sub lcd_busy_wait
'read lcd busy flag until busy=0
WAITST CON 1        ' delay 1us
busy var bit
lcd_busy_wait:
    busy = 1
    TRISB = TRISB or $F0        'set PORTB D4-D7 to inputs
    @ bcf LCD_RSREG, LCD_RSBIT  'RS=0
    @ bsf LCD_RWREG, LCD_RWBIT  'RW=1
    pauseus WAITST

    'wait for lcd busy flag (D7) to be low
    do while (busy = 1)
        @ bsf LCD_EREG, LCD_EBIT    'EN=1
        pauseus WAITST
        busy = PORTB.7              'read busy bit (bit 7 in upper nibble)
        @ bcf LCD_EREG, LCD_EBIT    'EN=0
        pauseus WAITST
        ' dummy read of lower nibble
        @ bsf LCD_EREG, LCD_EBIT    'EN=1
        pauseus WAITST
        @ bcf LCD_EREG, LCD_EBIT    'EN=0
        pauseus WAITST
    loop

    TRISB = TRISB and not $F0       'set PORTB D4-D7 back to outputs
    @ bcf LCD_RWREG, LCD_RWBIT      'RW=0
 return

You might find that you need to split the cursor position commands and data...

Code:

    call lcd_busy_wait
    lcdout $FE,$80        'move cursor
    call lcd_busy_wait
    lcdout "BU BiR DENEMEDiR"   'send data

Even with doing things like this some displays just don't like being continuously written to and you need to use delays.
Reading the BUSY flag really needs to be done for each byte transferred, so it may not help much at all.

Thanks for your great effort but now it doesn't show anything on the display ..

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