Changing LCD display refresh rate

[Charles Linquis]

A slightly different method:

Updating LCDs is really time consuming, from a PIC viewpoint. I find that a .25(once every 4 seconds) update rate is about right for most people, especially if it a two-line display.

The code below lets your code run at full speed and updates the LCD once every 4 seconds. Of course the rate can be changed to suit the user. It uses an ASM interrupt for low overhead.
Of course, you could read the timer directly, but I find that I always need interrupts anyway.

      DEFINE OSC 4 

     MasterClock VAR WORD BANKA SYSTEM
;----------------Timer Setup-----------------------------------  
    T0CON = 000010 ; /1:8   prescaler, tmr0 ON
;
;-------------------------------------------------------------     
   
INCLUDE "DT_INTS-18.bas"    '
;---------------------------------------------------------------
asm
    INT_LIST  macro     
        INT_Handler    TMR0_INT,  MainTimer, ASM, yes
       endm
    INT_CREATE              
endasm
''----------------- Initialization Done! -----------------------------
    Goto OverInt 
;----------------------- Timer INt ------------------------------------    
ASM
MainTimer
        movlw   0xCF         ;  100 mSec @ 4MHz
        movwf   TMR0H
        movlw   0x2C
        movwf   TMR0L
       
        btfsc   MasterClock + 1,7     ; Don't let MasterClock roll over
        bra     DontCount
        infsnz  MasterClock
        incf    MasterClock + 1          
        
      
DontCount        
      
      bcf     INTCON,2
    INT_ENABLE TMR0_INT
    INT_RETURN
ENDASM
;---------------------------------------------------------------------
OverInt:

   INTCON.7 = 1  ; Main Ints
   INTCON.6 = 1  ; Peripheral ints

    MasterClock = 0
@ bcf INTCON,2
@ INT_ENABLE TMR0_INT
TopOfLoop:
    If MasterClock >= 20 then     ; 20 X .1 sec = 2 seconds
       MasterClock = 0
         
         ; Do LCD routines here
    endif
    
        ; Your main program here
        
        goto TopOfLoop