Speed optimization (framebuffer scrolling)

**richard** · - 11th October 2022, 09:42

18f26k22

i have not tried much with Q43 yet , but
they have no ram below bank 5.
i dont know what bank pbp defaults to for them bank0 makes no sense at all , before them pbp kinda assumes bank0 before and after calls.
the instruction set is slightly different. movfffl or whatever
there may be other weird shit with indirect addressing

i have some q43's i just lack the enthusiasm to learn about them when the tried and trusty k22 serves my needs

**richard** · - 11th October 2022, 09:48

try them in bank6
and just remove the banksel 0 at the end

i added a rotate left to and a few tweaks

Code:

'****************************************************************'*  Name    : UNTITLED.BAS                                      *
'*  Author  : richard                                           *
'*  Notice  : Copyright (c) 2022 caveat emptor                  *
'*          : All Rights Reserved                               *
'*  Date    : 11/10/2022                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          : pic18f26k22                                                  *
'****************************************************************
#CONFIG
  CONFIG  FOSC = INTIO67
  CONFIG  PLLCFG = ON
  CONFIG  PRICLKEN = ON
  CONFIG  FCMEN = OFF
  CONFIG  IESO = OFF
  CONFIG  PWRTEN = ON
  CONFIG  BOREN = SBORDIS
  CONFIG  BORV = 190
  CONFIG  WDTEN = OFF
  CONFIG  WDTPS = 32768
  CONFIG  CCP2MX = PORTC1
  CONFIG  PBADEN = OFF
  CONFIG  CCP3MX = PORTB5
  CONFIG  T3CMX = PORTC0
  CONFIG  HFOFST = ON
  CONFIG  P2BMX = PORTB5
  CONFIG  MCLRE = EXTMCLR
  CONFIG  STVREN = ON
  CONFIG  LVP = OFF
  CONFIG  XINST = OFF
  CONFIG  DEBUG = OFF
  CONFIG  CP0 = OFF
  CONFIG  CP1 = OFF
  CONFIG  CP2 = OFF
  CONFIG  CP3 = OFF
  CONFIG  CPB = OFF
  CONFIG  CPD = OFF
  CONFIG  WRT0 = OFF
  CONFIG  WRT1 = OFF
  CONFIG  WRT2 = OFF
  CONFIG  WRT3 = OFF
  CONFIG  WRTC = OFF
  CONFIG  WRTB = OFF
  CONFIG  WRTD = OFF
  CONFIG  EBTR0 = OFF
  CONFIG  EBTR1 = OFF
  CONFIG  EBTR2 = OFF
  CONFIG  EBTR3 = OFF
  CONFIG  EBTRB = OFF
#ENDCONFIG
    


    NumberOfDisplays  CON 36
    NumberOfRows  CON 10
    DEFINE OSC 64
    DEFINE DEBUG_REG PORTB
    DEFINE DEBUG_BIT 7
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0
    LATB.7=1
    bcnt       VAR BYTE   bank0
    dcnt       VAR BYTE   bank0
    BUFF       VAR BYTE[32]
    iteration  VAR word 
    OSCCON=$70
    OSCTUNE.6=1
    while ! osccon2.7 :WEND    ;wait for pll
    ANSELB=0
    ANSELC=0
    ANSELA=0 
    dspbuff var byte[380]
    clear
    trisc = %01111111 
    TRISB = %01111111
    TRISA = %11111111
    pause 1000
    debug 13,10,"ready",13,10
    LATc.7=0
    ;38x8 bits wide 10 bits high


main:
    iteration=0
    dspbuff[379]=3
    dspbuff[37]=3
    WHILE  iteration<610
        LATc.7=1
        gosub rotate_l
        LATc.7=0
        debug 13,10,dec iteration
        debug 13,10,bin8 dspbuff[379]," " ,bin8 dspbuff[378]," " ,bin8 dspbuff[343] ," ",bin8 dspbuff[342] 
        debug 13,10,bin8 dspbuff[37] ," " ,bin8 dspbuff[36] ," " ,bin8 dspbuff[1]   ," ",bin8 dspbuff[0] 
        pause 50
        iteration=iteration+1 
    WEND
    iteration=0
    dspbuff[379]=$c0
    dspbuff[37]=$c0
    WHILE  iteration<610
        LATc.7=1
        gosub rotate_R
        LATc.7=0
        debug 13,10,dec iteration
        debug 13,10,bin8 dspbuff[379]," " ,bin8 dspbuff[378]," " ,bin8 dspbuff[343] ," ",bin8 dspbuff[342] 
        debug 13,10,bin8 dspbuff[37] ," " ,bin8 dspbuff[36] ," " ,bin8 dspbuff[1]   ," ",bin8 dspbuff[0] 
        pause 50
        iteration=iteration+1 
    WEND
goto main    
    
    
    
    
rotate_r:  ' pic18
asm
    banksel _bcnt  ;ROW
    movlw   _NumberOfRows    ;10 rows  
    movwf   _bcnt
    movlw   high (_dspbuff)  ;BOTTOM OF BUFFER
    movwf   FSR0H    
    movlw   low  (_dspbuff)
    movwf   FSR0L
    movlw   low((_NumberOfDisplays + 2)*_NumberOfRows-1) ;TOP OF BUFFER
    ADDWF   FSR0L 
    movlw   high((_NumberOfDisplays + 2)*_NumberOfRows-1)    
    ADDWFC  FSR0H
    MOVLW   _NumberOfDisplays + 2;36 displays + 2 outside of display 
RROW  
    movwf   _dcnt        ;display
    bcf     STATUS, C
Rcol
    rrcf    POSTDEC0 ,f  ;PER display
    DECFSZ  _dcnt ,F
    BRA     Rcol
    BNC     RBNC
    bsf     PLUSW0,7     ;max displays would be 127 to use plusw
RBNC 
    DECFSZ  _bcnt ,F
    BRA     RROW
    banksel 0
    return
endasm
 rotate_l:  ' pic18
asm
    banksel _bcnt              ;ROW
    movlw   _NumberOfRows 
    movwf   _bcnt
    movlw   high (_dspbuff)    ;BOTTOM OF BUFFER
    movwf   FSR0H    
    movlw   low  (_dspbuff)
    movwf   FSR0L
LROW
    MOVLW   _NumberOfDisplays + 2;36 displays + 2 outside of display 
    movwf   _dcnt         ;display
    comf    WREG
    incf    WREG
    bcf     STATUS, C
Lcol
    rlcf    POSTINC0 ,f   ;PER display
    DECFSZ  _dcnt ,F
    BRA     Lcol
    BNC     LBNC
    bsf     PLUSW0,0       ;max displays would be 127 to use plusw
LBNC 
    DECFSZ  _bcnt ,F
    BRA     LROW
    banksel 0
    return
endasm

**richard** · - 11th October 2022, 10:21

with my suggestions it compiles for 18f47q43, whether it works is not tested . a quick browse of the q43 instruction set and access bank looks ok

**HenrikOlsson** · - 11th October 2022, 12:11

Bank 6 (or 7) doesn't work at all. I don't know what it's doing exactly. It does display the text but it does not scroll it.

Bank 5 (or 25) works - sort of.
I can scroll it left OR right continously without issues but when I change direction whatever is in the non visible part the buffer comes back on to the display shifted down by one row - at least I think that's what happening.

But it's fast, that's for sure.
* Mine was like 7ms or something like that
* tumblweeds was more than twice as fast at 3ms.
* Richards comes in at 0.2ms - amazing.

Mine and tumbleweeds simply scrolls the display, anything that's shifted outside of the buffer is lost while Richards rotates it so they're not exactly the same.

/Henrik.

**tumbleweed** · - 11th October 2022, 12:54

On most of the Q family the SFR registers are in banks 0-4, and the start of user ram is in bank 5.
That's where the access bank is (0x500-0x55F). The other part of the access bank is at 0x460-0x4FF, but that's for the fast SFR registers so you can't use that.
So, the "default" setting for 'banksel' should be 5 and not 0.

If you use the MOVFF instruction both the source and destination must be in the first 4K of ram space.
If either are outside that you need to use MOVFFL, which is a three-word instruction so it's more code (and slower) than MOVFF.

The K42/K83 force you to use MOVFFL to access SFR registers outside the access bank since on those the SFR regs are at the very top of ram.
That's one reason to skip the K42 and use the Q43 instead.

**richard** · - 11th October 2022, 23:43

I can scroll it left OR right continously without issues but when I change direction whatever is in the non visible part the buffer comes back on to the display shifted down by one row - at least I think that's what happening.

i expected to have had the buffer cleared out and reset before a direction change . however that sort of behavior is unanticipated

* Richards comes in at 0.2ms - amazing.

i get 0.1mS , maybe my oscilloscope is off

one of my clients sent me a test jig for q43 chips yesterday. i need to get into them soon i guess
no more excuses

@tumbleweed for confirming what i thought

**richard** · - 12th October 2022, 02:45

just for interest i tried my code on the st7920 buffer for rows 8 to 15 for the full 16 byte width of course

works as expected even when direction reversed midstream