Help with LCD Scroll

[Art]

So since that was meaningless if you can’t scroll on LCD already, I’ll try an example.

string var byte [16] ‘ because I assume it’s one line of a 2x16 display but you can change this
character var byte ‘ the current character
counter var byte ‘ a step counter and index
lindex var byte ‘ a lookup table index

Now how you’re getting the string in the first place you didn’t say, it could be being typed in serial,
or already stored in eprom or something. I’ll go with a longer than 16 char message stored in lookup table,
and put it in a subroutine at the end of the program.

lookuptable: ‘ get the next character from the table into the character buffer
LOOKUP lindex,[“CHECK IT OUT A SCROLLING TEXT DEMO!!!”],character ‘ 0-36 length message (37 characters in Human talk)
return

We need something to actually rotate the 16 char line buffer and drop the oldest byte off the end
whenever a new character is shifted in. This goes in a subroutine also at the end of the program.

'
rotatearray:				‘ rotate line array
for counter = 16 to 1 step - 1
string[counter] = string[counter-1]
next counter
string[0] = character			‘ insert new character byte at zero index
return
‘

Then a main cycle is needed to index the lookup table, call the lookup and rotate routines and
print the line to LCD. After the variable declarations and before the subroutines:

lindex = 0
CLEARLCD ‘ it’s been a while since I looked at LCDOUT, but whatever two byte code to clear LCD and home.
'
cycle:
HOMELCD ‘ it’s been a while since I looked at LCDOUT, but whatever two byte code to home LCD cursor.
'
gosub lookuptable
lindex = lindex + 1 ‘ increment lookup index
if lindex > 36 then ‘ limit lookup index to length of message
lindex = 0
endif
gosub rotatearray ‘ rotate line with new character at zero index

for counter = 0 to 15 ‘ print the line to lcd
LCDOUT string[counter]
next counter

pause 1000 ‘ delay to see one movement per second

goto cycle ‘ do cycle forever

Largely untested so if someone has a simulation with LCD pls feel free to run it

[Tabsoft]

Art,

I ran your suggestions through a simulator and a couple of things.
1. Scrolls from Left to Right, ozarkshermit wanted Right to Left.
2. Characters are in reverse order. Should read for 20 chars on the screen "CHECK IT OUT A SCROL", but comes out "LORCS A TUO TI KCEHC"

So I took your example and modified it to change these items.

I put this together for a 18F4620.
Compiles and runs fine in the simulator.

'*****PIC MCU Configuration Fuses (MPASM)*****
#IF __PROCESSOR__ = "18F4620"
    #CONFIG
        CONFIG OSC = ECIO6            ; EC oscillator, port function on RA6
        CONFIG  WDT = OFF             ; WDT disabled (control is placed on the SWDTEN bit)
        CONFIG  FCMEN = OFF           ; Fail-Safe Clock Monitor disabled
        CONFIG  IESO = OFF            ; Oscillator Switchover mode disabled
        CONFIG  PWRT = OFF            ; PWRT disabled
        CONFIG  BOREN = SBORDIS       ; Brown-out Reset enabled in hardware only (SBOREN is disabled)
        CONFIG  BORV = 3              ; Minimum setting
        ;CONFIG  WDT = ON              ; WDT enabled
        CONFIG  WDTPS = 512           ; 1:512
        CONFIG  CCP2MX = PORTC        ; CCP2 input/output is multiplexed with RC1
        CONFIG  PBADEN = OFF          ; PORTB<4:0> pins are configured as digital I/O on Reset
        CONFIG  LPT1OSC = OFF         ; Timer1 configured for higher power operation
        CONFIG  MCLRE = ON            ; MCLR pin enabled; RE3 input pin disabled
        CONFIG  STVREN = ON           ; Stack full/underflow will cause Reset
        CONFIG  LVP = OFF             ; Single-Supply ICSP disabled
        CONFIG  XINST = OFF           ; Instruction set extension and Indexed Addressing mode disabled (Legacy mode)
        CONFIG  DEBUG = OFF           ; Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins
        CONFIG  CP0 = OFF             ; Block 0 (000800-003FFFh) not code-protected
        CONFIG  CP1 = OFF             ; Block 1 (004000-007FFFh) not code-protected
        CONFIG  CP2 = OFF             ; Block 2 (008000-00BFFFh) not code-protected
        CONFIG  CP3 = OFF             ; Block 3 (00C000-00FFFFh) not code-protected
        CONFIG  CPB = OFF             ; Boot block (000000-0007FFh) not code-protected
        CONFIG  CPD = OFF             ; Data EEPROM not code-protected
        CONFIG  WRT0 = OFF            ; Block 0 (000800-003FFFh) not write-protected
        CONFIG  WRT1 = OFF            ; Block 1 (004000-007FFFh) not write-protected
        CONFIG  WRT2 = OFF            ; Block 2 (008000-00BFFFh) not write-protected
        CONFIG  WRT3 = OFF            ; Block 3 (00C000-00FFFFh) not write-protected
        CONFIG  WRTC = OFF            ; Configuration registers (300000-3000FFh) not write-protected
        CONFIG  WRTB = OFF            ; Boot Block (000000-0007FFh) not write-protected
        CONFIG  WRTD = OFF            ; Data EEPROM not write-protected
        CONFIG  EBTR0 = OFF           ; Block 0 (000800-003FFFh) not protected from table reads executed in other blocks
        CONFIG  EBTR1 = OFF           ; Block 1 (004000-007FFFh) not protected from table reads executed in other blocks
        CONFIG  EBTR2 = OFF           ; Block 2 (008000-00BFFFh) not protected from table reads executed in other blocks
        CONFIG  EBTR3 = OFF           ; Block 3 (00C000-00FFFFh) not protected from table reads executed in other blocks
        CONFIG  EBTRB = OFF           ; Boot Block (000000-0007FFh) not protected from table reads executed in other blocks

    #ENDCONFIG
#else
    #ERROR "This program requires a PIC 18F4620 MCU"
#endif

OSCCON = $60  ' Set PIC to 4Mhz & ECIO Clock Mode
'*****END PIC Configuration*****

'*****Defines*****
define OSC 4            ' Set clock to 4Mhz in PIC Basic
'*****Define LCD registers and bits*****
define LCD_BITS      4
define LCD_LINES     2
Define LCD_DREG      PORTD
Define LCD_DBIT      4
Define LCD_RSREG     PORTE
Define LCD_RSBIT     0
Define LCD_EREG      PORTE
Define LCD_EBIT      1
define LCD_RWREG     PORTE
define LCD_RWBIT     2
define LCD_COMMANDUS 1500
define LCD_DATAUS    44
'*****END Defines*****

    ADCON0.0 = 0  ' A/D Converter module is disabled   
    ADCON1 = $0F  ' %0000 1111 AN2=VSS, AN3=VDD, AN12-0 = Digital 
    ADCON2 = $00  ' %0000 0000
    TRISA = 0
    TRISB = 0
    TRISC = 0
    TRISD = 0
    TRISE = 0
    

string var byte[20] ' because I assume it’s one line of a 2x20 display but you can change this
character var byte ' the current character
counter var byte ' a step counter and index
lindex var byte ' a lookup table index

    ' Initialize LCD
    Low PORTE.2       ' LCD R/W low = write
    Pause 100         ' Wait for LCD to startup
    
    LCDOUT $fe,1,"Startup"
    pause 1000



start:
    lindex = 0
    lcdout $fe,1    'CLEARLCD  it’s been a while since I looked at LCDOUT, but whatever two byte code to clear LCD and home.

cycle:
    lcdout $fe, $02 'HOMELCD  it’s been a while since I looked at LCDOUT, but whatever two byte code to home LCD cursor.
    gosub lookuptable
    lindex = lindex + 1 ' increment lookup index
    if lindex > 37 then ' limit lookup index to length of message
        lindex = 0
    endif
    gosub rotatearray ' rotate line with new character at zero index
    
    for counter = 0 to 19 ' print the line to lcd
        LCDOUT string[counter]
    next counter
    pause 1000 ' delay to see one movement per second
    
    goto cycle ' do cycle forever


lookuptable: ' get the next character from the table into the character buffer
    LOOKUP lindex,["CHECK IT OUT A SCROLLING TEXT DEMO!!! "],character ' 0-37 length message (38 characters in Human talk)
return

rotatearray:				' rotate line array
    for counter = 0 to 18 step 1
        string[counter] = string[counter+1]
    next counter
    string[19] = character    
return

[Art]

Lol, thanks, there will always be something off when you don’t actually run it

Thing is I was reading about string support in the wish list section and thought to myself
a string is just a character array with a zero value at the end of it.
All of the C functions: string length, string compare, sprint, etc. can all be written into BASIC easily.

[ozarkshermit]

Thanks to all the responses.

Eventually I came up with the lookup table approach, sending one character at a time, and of course it works. The display was just too "jerkey" for my tastes.

In all the various scrolling approaches linked to, none of them use a "conventional" scroll on a 4 line LCD, and prohibit the scroll from "wrapping" to line 3.

Disabling the "line wrap" simply is not possible, IMHO.

Ken

[Art]

I’m not sure what you mean there by “disabling line wrap not possible”.
Did you get what you want done?

[ozarkshermit]

Thanks Art

See my first post in this thread. I have not been able to accomplish that

Ken

[Art]

The way I read it, that should be what the version Tabsoft posted does.
I might be seeing something else in my mind, or does it just scroll the wrong direction?

Basically, this could be written simpler if it never had to be a real program.
You could ditch the line buffer and rotate routine, step the index where you read the lookup table,
check it’s bounds, and write 20 char to LCD at a time directly to LCD.

Usually you want to look at, or change the display data, so I’d normally prepare
all lines of text in buffers, and write all four lines from the line's start positions for every frame.
even if the text doesn’t change or move.
If you never write past the end of a line the text can’t wrap.