Problems with LCD display

[fratello]

I recently bought some LCD's ; all are made in PRC, and "full compatible with HD44780 standard".
I try to use with an "old" schematic (with an "old" display (model -PRC 1602 A) this schematic work without any problem !).
But ... with original code (with only this : "LCDOUT $FE, 1, $FE, $0C" line ), none of them is initialized correctly on first "start" !
I put one picture with ...stranges characters that appear on the display (to all of them !).
After modification of program, they go right ... in 7 cases of 10 (I mean when I power on the schematic ...).

DEFINE LCD_DREG PORTC           ' LCD on port c
DEFINE LCD_DBIT 0               ' Data bits C0..C3
DEFINE LCD_RSREG PORTA          ' RS on PORTA
DEFINE LCD_RSBIT 1              ' RS on A1 
DEFINE LCD_EREG PORTA           ' E on PORTA
DEFINE LCD_EBIT 2               ' E on A2
DEFINE LCD_BITS 4               ' LCD 4 bit mode
DEFINE LCD_LINES 2              ' 2 line LCD display
Define LCD_COMMANDUS 2000       ' Command Delay (uS)
Define LCD_DATAUS 50            ' Data Delay (uS)


LCDOUT $FE,1:PAUSE 3000:LCDOUT $FE,1         ' Initialize LCD WITH HUGE PAUSE !!!
Pause 3000                    ' AND AGAIN ... 
LcdOut $FE, $80," DUAL TERMOMETER "
LcdOut $FE, $C0,"  AND THERMOSTAT "
PAUSE 5000                    ' AND AGAIN ...
LCDOUT $FE, 1, $FE, $0C                 ' Clear display, cursor off
Pause 1000

What can I do in this case ? Thanks in advance for any suggestion !

[HenrikOlsson]

Try increasing the LCD_COMMANDUS and LCD_DATAUS. Double or tripple them, if it OK then work your way down to the lowest values that works. Alternatively look in the datasheet for the specified delay needed.

[fratello]

I already try this, BEFORE increasing Pause ... I discovered the "scroll" code dont work fine too...I think these displays are "stinky" !

[Sherbrook]

I have had this problem with some cheap displays, they are slow to start up.
Try a pause before initializing

PAUSE 1000
LCDOUT $FE,1

Phil

[Archangel]

Hi Fratello,
I found it helps to add bypass capacitors on the power inputs of these too.

[fratello]

Thanks !
I found this great piece of code (Thanks to Mr.Darell !!!) ; ALL my LCD's work fine now !!!

GOSUB LCD_INIT                            ' Do manual LCD Initialization

;---- Manual LCD Initialization -------------------------------------
LCD_INIT:
    @ MOVE?CT  0, LCD_RSREG,LCD_RSBIT     ; Start with RS LOW
    @ MOVE?CT  0, LCD_RSREG+80h,LCD_RSBIT ; RS is OUTPUT
    
    @ MOVE?CT  0, LCD_EREG,LCD_EBIT       ; Start with Enable LOW
    @ MOVE?CT  0, LCD_EREG+80h,LCD_EBIT   ; Enable is OUTPUT

    @ MOVE?CT  0, LCD_DREG+80h,LCD_DBIT   ; Data Bus is OUTPUT
    @ MOVE?CT  0, LCD_DREG+80h,LCD_DBIT +1
    @ MOVE?CT  0, LCD_DREG+80h,LCD_DBIT +2
    @ MOVE?CT  0, LCD_DREG+80h,LCD_DBIT +3
    
    PAUSE 1000
    BUSdata = 3
    GOSUB Send4Bit : pause 8              ; FunctionSet 4 times
    GOSUB Send4Bit : pauseUS 200
    GOSUB Send4Bit : pauseUS 200
    GOSUB Send4Bit : pauseUS 200
    BUSdata = 2  :  GOSUB Send4Bit        ; 4-bit mode

    BUSdata = 2  :  GOSUB Send4Bit        ; 2-line, 5x7
    BUSdata = 8  :  GOSUB Send4Bit        
    
    BUSdata = 0  :  GOSUB Send4Bit        ; Display OFF
    BUSdata = 8  :  GOSUB Send4Bit
    
    BUSdata = 0  :  GOSUB Send4Bit        ; Display Clear
    BUSdata = 1  :  GOSUB Send4Bit
    PAUSE 3

    BUSdata = 0  :  GOSUB Send4Bit        ; Entry Mode Set
    BUSdata = 6  :  GOSUB Send4Bit
    PAUSE 3
    
    BUSdata = 0  :  GOSUB Send4Bit        ; Display ON
    BUSdata = $C :  GOSUB Send4Bit
    
    @  MOVE?CT 1, LCDINITFLAG   ; Tell PBP LCD is already Initialized
return


Send4Bit:
    @ MOVE?CT  1, LCD_EREG,LCD_EBIT       ; Enable LCD
@   MOVE?BB  LCD_DREG, _TempB             ; Put Data on the Bus R-M-W
@   if LCD_DBIT == 0                      ;   Bus starts at 0
        TEMPB = (TEMPB & $F0) | BUSdata
@   else                                  ;   Bus starts at 4
        TEMPB = (TEMPB & $0F) | (BUSdata << 4)
@   endif
@   MOVE?BB  _TempB, LCD_DREG  
    
    PAUSEUS 25                            ; Keep enabled extra long
    @ MOVE?CT  0, LCD_EREG,LCD_EBIT       ; Disable LCD
    Pauseus 50
return
;---------- END LCD_INIT --------------------------------------------

[Darrel Taylor]

That's awesome!

It didn't work for the guy I wrote it for 6 years ago.
I'm glad to see it fixed your problem!

Thanks fratello.

[fratello]

I THANK YOU ! Glad to be member of this forum, where I "met" so special people ... Best regards !