8x8 LED matrix "smooth" horizontal scrolling text - what's the math?

[flotulopex]

Hello there,

I'm trying to make my 8x8 LED matrix display (1 module) to smoothly scroll horizontally text (or simply letters) from right to left.

I started thanks to PBPBeginner and his example.

Unfortunately, the example does "scroll" (shift) one caracter after the other meaning there is no close link between the displayed caracters and the next one; they shift from right to left one at the time.

I think there must be a way or an algorythm to calculate how to "append" the next caracter (or frame) to the currently display and make everything move from right to left.

For my tests, I designed two simple caracters here and to save my day, I designed all intermediate frames - but this is obvioulsy the wrong way to go and a huge waist of time.



Letter A
HEX 0024243c24241800
DEC 0, 36, 36, 60, 36, 36, 24, 0

Letter B
HEX 001c24241c241c00
DEC 0, 28, 36, 36, 28, 36, 28, 0

Does anyone have an example or point me on how I must calculate the transition steps please?

In a perfect world, I even should be able to trim some vertical empty lines of the frames to make the caracters appear close one to the other....

But I would appreciate a first simple start method to calculate this data to scroll.

'======= FUSES ====================================================================================
' PIC 16F690 Fuses

' Internal oscillator  (activate OSCCON register)
@ __config _FCMEN_OFF &_IESO_OFF &_CPD_OFF &_WDT_OFF &_INTRC_OSC_NOCLKOUT &_BOR_OFF &_CP_OFF &_PWRTE_OFF &_MCLRE_OFF

@ ERRORLEVEL -306
@ ERRORLEVEL -202

'-------------------------------------------------------------------------------
' Registers   76543210
OPTION_REG = %10000000 'PORT A&B Pull-Ups disabled (look WPUA & WPUB)
OSCCON     = %01110000 'Internal RC set to 8Mhz
ANSEL      = %00000000 'Analog inputs Channels 0 to 7
ANSELH     = %00000000 'Analog inputs Channels 8 to 11
WPUA       = %00000000 'Weak pull-ups
WPUB       = %00000000 'Weak pull-ups
ADCON0     = %00000000 'A/D Module (OFF)
CM1CON0    = %00000000 'Comparator1 Module (OFF)
CM2CON0    = %00000000 'Comparator2 Module (OFF)
INTCON     = %00000000 'INTerrupts CONtrol
TRISA      = %00000000 'Set Input/Output (0 to 5)
PORTA      = %00000000 'Ports High/Low (0 to 5)
TRISB      = %00000000 'Set Input/Output (4 to 7)
PORTB      = %00000000 'Ports High/Low (4 to 7)
TRISC      = %00000000 'Set Input/Output (0 to 7)
PORTC      = %00000000 'Ports High/Low (0 to 7)
                                
' ====== DEFINES ==================================================================================
define OSC 8
DEFINE NO_CLRWDT 1

' ====== VARIABLES ================================================================================
ADDRESS     var word    ' display's address
DATAREG     var word    ' display's data register
Y           VAR BYTE    ' just a counter
X           var BYTE    ' horizontal scroll steps counter
DES         VAR BYTE
ScrollSpeed var word    ' pause time
Letter_Cnt  VAR BYTE    ' caracter to be displayed
CLK         VAR PORTB.4 ' connected to module's CLK
LOAD        VAR PORTB.5 ' connected to module's CS
DAT         VAR PORTB.6 ' connected to module's DIN

' ====== INITIALIZE ===============================================================================
low clk
low dat
low load  'CS
ScrollSpeed = 400
Letter_Cnt  = 1

' ====== MAX7219 SETUP ============================================================================
ADDRESS = $0C : DATAREG = $01 : gosub MaxWrite ' SHUTDOWN=0, NORMAL OPERATION=1
ADDRESS = $09 : DATAREG = $00 : gosub MaxWrite ' DECODE-MODE, NO DECODE
ADDRESS = $0A : DATAREG = $00 : gosub MaxWrite ' LEDS INTENSITY MIN=0, MAX=F
ADDRESS = $0B : DATAREG = $07 : gosub MaxWrite ' NUMBER OF DISPLAYED LINES
ADDRESS = $0F : DATAREG = $00 : gosub MaxWrite ' DISPLAY-TEST (0=OFF, 1=ON)
GOSUB CLEAR_ALL
               
' ====== PROGRAM ==================================================================================
INIT:

'FOR Letter_Cnt = 1 to 2
'    FOR Y = 0 TO 7
'        IF Letter_Cnt = 1 THEN lookup y,[  0, 36, 36, 60, 36, 36, 24,  0],datareg ' A
'        IF Letter_Cnt = 2 THEN lookup y,[  0, 28, 36, 36, 28, 36, 28,  0],datareg ' B
'        ADDRESS = Y + 1
'        GOSUB MAXWRITE
'        PAUSE 10
'    NEXT Y
'    PAUSE ScrollSpeed
'NEXT Letter_Cnt
'GOTO INIT


des = 0
for x = 0 to 6
    for y = 0 to 6
        lookup y,[  0, 36, 36, 60, 36, 36, 24,  0],datareg ' A
        address = y+1
        datareg = datareg >> des
        gosub maxwrite
        pause 10
    next y
    pause ScrollSpeed
    des = des + 1
next x

des = 0
for x = 0 to 6
    for y = 0 to 6
        lookup y,[  0, 28, 36, 36, 28, 36, 28,  0],datareg ' B
        address = y+1
        datareg = datareg >> des
        gosub maxwrite
        pause 10
    next y
    pause ScrollSpeed
    des = des + 1
next x

GOSUB CLEAR_ALL

GOTO INIT

END

' ====== SUBROUTINES ==============================================================================
MaxWrite:
    shiftout DAT,CLK,1,[ADDRESS,DATAREG] 'Shift out the data to the 'MAX7219 'first the address, then data.
    pulsout LOAD,1 'load the data into the MAX7219
    PAUSE 10
    return

CLEAR_ALL:
    for Y = 1 to 7 'write $0F (blank) to all digits
        ADDRESS = Y
        DATAREG = $00
        gosub MaxWrite
    next Y
    return

'Letter A single dots (HEX 0024243c24241800)
'  0, 36, 36, 60, 36, 36, 24,  0

'Letter B single dots (HEX 001c24241c241c00)
'  0, 28, 36, 36, 28, 36, 28,  0

'Letter C single dots (HEX 0018240404241800)
'  0, 24, 36,  4,  4, 36, 24,  0