Changing LCD display refresh rate

**pxidr84** · - 3rd November 2011, 18:15

Hi everyone,

In my program, the LCD commands are placed in a loop.

But the refresh rate of the LCD is too fast, so in certain conditions (when reading an unstable ADC value for example), the displayed numbers are changing very quickly, so it's unreadable.

So, it will be better if my LCD refresh displayed values every 200/500ms.

I don't want to use a delay/wait command in my loop.

Did the DEFINE LCD [...] commands can solve this problem?

Thanks a lot.

**cc1984** · - 3rd November 2011, 18:59

Why not just add a condition that only updates the LCD if the ADC value changes by a certain amount from the last reading. That would reduce the updates and also make it less resposive to small changes in voltage.

**rsocor01** · - 3rd November 2011, 19:32

Well, this is just an idea. Take 10 readings, then obtain the average, and display it in the LCD. Something like this,

Code:

MAIN:

FOR I = 0 TO 9
  ....Take ADC reading READING[I] 
NEXT I

'Next obtain the average
AVERAGE = (READING[0] + READING[1] + ......) / 10

LCDOUT $FE, 1, DEC AVERAGE

GOTO MAIN

Robert

**pxidr84** · - 3rd November 2011, 19:33

How do that?

Here is a sample of my loop :

lp:

ADCON0.1=%1
WHILE ADCON0.1=%1:WEND

' Store ADC results
isense.HIGHBYTE=ADRESH
isense.LOWBYTE=ADRESL

' Security fault verifications
IF isense**40000>imax THEN flt=1

' LCD
idisp=isense**40000
lcdout $fe,$c0,$1,$20,"1 ISENS: ",DEC idisp DIG 2,DEC idisp DIG 1,".",DEC idisp DIG 0,"A"

goto lp

**Acetronics2** · - 3rd November 2011, 19:44

Code:

lp:

ADCON0.1=%1 
WHILE ADCON0.1=%1:WEND

' Store ADC results 
isense.HIGHBYTE=ADRESH 
isense.LOWBYTE=ADRESL

' Security fault verifications
IF isense**40000>imax THEN flt=1

I = I+1    ; insert @top " I var Byte " 
IF I = 1 THEN  ; also can use IF I // 200 = 1 ... and adjust "200" to the desired rate

' LCD
idisp=isense**40000
lcdout $fe,$c0,$1,$20,"1 ISENS: ",DEC idisp DIG 2,DEC idisp DIG 1,".",DEC idisp DIG 0,"A"

ENDIF


goto lp

**rsocor01** · - 3rd November 2011, 19:58

Originally Posted by pxidr84

How do that?

Something like this,

Code:

lp:

AVERAGE = 0
FOR I = 0 TO 9
  ADCON0.1=%1 
   WHILE ADCON0.1=%1:WEND

   ' Store ADC results 
   isense.HIGHBYTE=ADRESH 
   isense.LOWBYTE=ADRESL
   
   AVERAGE = AVERAGE + isense
NEXT I

AVERAGE = AVERAGE / 10
ISENSE = AVERAGE

' Security fault verifications
IF isense**40000>imax THEN flt=1

' LCD
idisp=isense**40000
lcdout $fe,$c0,$1,$20,"1 ISENS: ",DEC idisp DIG 2,DEC idisp DIG 1,".",DEC idisp DIG 0,"A"


goto lp

**Charles Linquis** · - 4th November 2011, 00:03

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.

Code:

      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

**pxidr84** · - 4th November 2011, 09:49

There is no @ int_return at the end?
I already use a timer1 DT interrupt, this one will not affect my program?

**pxidr84** · - 4th November 2011, 12:09

Note : I use a 40MHz xtal, and my LCD desired refresh rate is about 0.5s.

**Charles Linquis** · - 4th November 2011, 13:10

The ISR is not written in PBP. It is in assembly. The only INT_RETURN you need is at the end of the interrupt service routine - just before the ENDASM.

For 40Mhz -
Lines you need to change

DEFINE OSC 40
T0CON = %10000011 ; Turn timer on, divide by 16 prescaler

movlw 0x0B ; 100 mSec @ 40MHz
movwf TMR0H
movlw 0xDC
movwf TMR0L

If MasterClock >= 5 then ; 5 X .1 sec = .5 seconds

And no, it will not affect anything else you have running.

**pxidr84** · - 6th November 2011, 09:57

Ok, so I've integrated a very simple counter whos counts the number of loops and refresh the LCD after a certain amount of loops :

Code:

' Main entire program loop
lp:


' Start ADC conversion
ADCON0.1=%1       
WHILE ADCON0.1=%1:WEND


' Store ADC results   
isense.HIGHBYTE=ADRESH 
isense.LOWBYTE=ADRESL
usense.HIGHBYTE=ADRESH 
usense.LOWBYTE=ADRESL
tsense.HIGHBYTE=ADRESH 
tsense.LOWBYTE=ADRESL
psense.HIGHBYTE=ADRESH 
psense.LOWBYTE=ADRESL 


' Security fault verifications
IF isense**40000>imax THEN flt=1
IF usense>880 THEN flt=2
IF tsense>880 THEN flt=3


' Security fault tripping
IF flt>0 THEN GOTO fltsub


' Brake/surge resistor control
IF usense>800 then
   if run=%1 then high PORTD.7
else
    LOW PORTD.7
endif
                                                                                                      
' Frequency reference control by potentiometer
psense=((psense<<6)**maxf)+10
IF psense<>freq+10 THEN freq=psense:flag=%1


' Frequency limits
IF freq<minf THEN freq=minf
IF freq>maxf THEN freq=maxf


' Recalculations
IF flag=%1 THEN


   ' Reload timer calculation
   dum=dum1*dum2
   stor=DIV32 freq
   rld=(65535-stor)+8


   ' U/F calculation
   IF freq<=500 THEN
      amp=(freq*131)+35
   ELSE
       amp=65535
   ENDIF


  flag=%0
ENDIF


' Run
IF run=%1 THEN 
   IF flag1=%0 THEN PWMCON0.6=%1:HIGH PORTD.6:flag1=%1
ENDIF


' Stop
IF run=%0 THEN
   IF flag1=%0 THEN PWMCON0=%0:LOW PORTD.6:flag1=%1
ENDIF


' FWD rotation
IF rot=%1 THEN
   IF flag2=%0 THEN ustep=89:vstep=59:wstep=29:write 0,rot:flag2=%1
ENDIF


' RWD rotation
IF rot=%0 THEN
   IF flag2=%0 THEN ustep=29:vstep=59:wstep=89:write 0,rot:flag2=%1
ENDIF


' - button
IF PORTE.0=%1 then
   if flag8=%0 then
      IF menu=%0 THEN mpos=mpos-1:d=1200:E=%0:F=%0
   ENDIF
   flag8=%1
endif


' + button
IF PORTE.1=%1 then
   if flag9=%0 then
      IF menu=%0 THEN mpos=mpos+1:d=1200:E=%0:F=%0
   endif
   flag9=%1
endif


' Run/stop button
IF PORTC.0=%1 THEN
   IF run=%0 AND mpos<6 AND flag3=%0 THEN run=%1:flag1=%0:flag3=%1:f=%0
   IF run=%1 AND flag3=%0 THEN run=%0:flag1=%0:flag3=%1:f=%0
ENDIF


' FWD/RWD button
IF PORTC.1=%1 THEN
   IF rot=%0 AND run=%0 AND flag4=%0 THEN rot=%1:flag2=%0:flag4=%1
   IF rot=%1 AND run=%0 AND flag4=%0 THEN rot=%0:flag2=%0:flag4=%1
ENDIF


' Menu/OK button
IF PORTC.2=%1 THEN
   IF menu=%0 AND run=%0 AND mpos>5 AND flag5=%0 THEN menu=%1:flag5=%1
   IF menu=%1 AND flag5=%0 THEN menu=%0:flag5=%1
ENDIF


' Buttons released state
IF PORTC.0=%0 THEN flag3=%0
IF PORTC.1=%0 THEN flag4=%0
IF PORTC.2=%0 THEN flag5=%0
IF PORTE.0=%0 THEN flag8=%0
IF PORTE.1=%0 THEN flag9=%0


' LCD first line writing
c=c+1
if c>800 then
   IF rot=%1 THEN LCDOUT $fe,$2,"+" 
   IF rot=%0 THEN LCDOUT $fe,$2,"-"
   LCDOUT DEC freq DIG 3,DEC freq DIG 2,DEC freq DIG 1,".",DEC freq DIG 0,"Hz"
   IF run=%1 THEN LCDOUT REP 32\5,"RUN"
   IF run=%0 THEN LCDOUT REP 32\4,"STOP"
   c=0
endif


' Inverter menu (LCD second line writing)
SELECT CASE mpos


' Menu limits
IF mpos<1 THEN mpos=1
IF mpos>11 THEN mpos=11
IF run=%1 THEN
   IF mpos>5 THEN mpos=5
ENDIF


' Current sensing submenu
CASE 1
d=d+1
if d>1200 then
   idisp=isense**40000
   lcdout $fe,$c0,$1,$20,"1 ISENS: ",DEC idisp DIG 2,DEC idisp DIG 1,".",DEC idisp DIG 0,"A"
   d=0
endif


' Voltage sensing submenu
CASE 2
d=d+1
if d>1200 then
   udisp=usense**29600
   lcdout $fe,$c0,$1,$0,"2 USENS: ",DEC3 udisp,"V",32
   d=0
endif


' Temperature sensing submenu
CASE 3
d=d+1
if d>1200 then
     tdisp=(tsense-280)/8
     lcdout $fe,$c0,$1,$0,"3 TEMP: ",DEC tdisp DIG 1,DEC tdisp DIG 0,$df,"C",REP $20\2
     d=0
endif


' Last fault reading submenu
CASE 4
if e=%0 then
   lcdout $fe,$c0,$1,$0,"4 LASTFAULT: ",DEC1 lastf
   e=%1
endif


' Firmware version reading submenu
CASE 5
IF run=%1 THEN
   IF f=%0 then
      lcdout $fe,$c0,$1,$20,"5 FW: V2011.00"
      f=%1
   ENDIF
ENDIF
IF run=%0 THEN
   IF F=%0 THEN
      lcdout $fe,$c0,$1,$0,"5 FW: V2011.00"
      f=%1
   ENDIF
endif


' Maximum frequency adjust submenu
CASE 6
IF menu=%1 THEN
   Lcdout $fe,$c0,$3e,$3e,"A MAX: ",DEC maxf DIG 3,DEC maxf DIG 2,DEC maxf DIG 1,".",DEC maxf DIG 0,"Hz"
   BUTTON PORTE.0,1,200,10,a,0,ret
          IF maxf>minf THEN maxf=maxf-1
   ret:
   BUTTON PORTE.1,1,200,10,b,0,ret1
          IF maxf<1200 THEN maxf=maxf+1
   ret1:
   flag6=%0
ELSE
    lcdout $fe,$c0,$1,$0,"A MAX: ",DEC maxf DIG 3,DEC maxf DIG 2,DEC maxf DIG 1,".",DEC maxf DIG 0,"Hz"
    if flag6=%0 then write 1,maxf.HIGHBYTE:write 2,maxf.LOWBYTE:flag6=%1
ENDIF


' Minimum frequency adjust submenu
CASE 7
IF menu=%1 THEN
   Lcdout $fe,$c0,$3e,$3e,"B MIN: ",DEC minf DIG 3,DEC minf DIG 2,DEC minf DIG 1,".",DEC minf DIG 0,"Hz"
   BUTTON PORTE.0,1,200,10,a,0,ret2
          IF minf>10 THEN minf=minf-1
   ret2:
   BUTTON PORTE.1,1,200,10,b,0,ret3
          IF minf<maxf THEN minf=minf+1
   ret3:
   flag6=%0
ELSE
    lcdout $fe,$c0,$1,$0,"B MIN: ",DEC minf DIG 3,DEC minf DIG 2,DEC minf DIG 1,".",DEC minf DIG 0,"Hz"
    if flag6=%0 then write 3,minf.HIGHBYTE:write 4,minf.LOWBYTE:flag6=%1
ENDIF


' Current trip adjust submenu
CASE 8
IF menu=%1 THEN
   Lcdout $fe,$c0,$3e,$3e,"C ITRIP: ",DEC imax DIG 2,DEC imax DIG 1,".",DEC imax DIG 0,"A"
   BUTTON PORTE.0,1,200,20,a,0,ret4
          IF imax>0 THEN imax=imax-1
   ret4:
   BUTTON PORTE.1,1,200,20,b,0,ret5
          IF imax<150 THEN imax=imax+1
   ret5:
   flag6=%0
ELSE
    lcdout $fe,$c0,$1,$0,"C ITRIP: ",DEC imax DIG 2,DEC imax DIG 1,".",DEC imax DIG 0,"A"
    IF flag6=%0 THEN write 5,imax:flag6=%1
ENDIF


' PWM carrier frequency adjust submenu
CASE 9
IF menu=%1 THEN
   Lcdout $fe,$c0,$3e,$3e,"D PWMFREQ: ",DEC1 pwmf,REP $20\2 
   BUTTON PORTE.0,1,200,50,a,0,ret6
          IF pwmf>1 THEN pwmf=pwmf-1
   ret6:
   BUTTON PORTE.1,1,200,50,b,0,ret7
          IF pwmf<4 THEN pwmf=pwmf+1
   ret7:
   flag6=%0
ELSE
    lcdout $fe,$c0,$1,$0,"D PWMFREQ: ",DEC1 pwmf,REP $20\2
    IF flag6=%0 THEN write 6,pwmf:GOSUB pwmsub:flag6=%1
ENDIF


' LCD backlight submenu
CASE 10
IF menu=%1 THEN
   Lcdout $fe,$c0,$3e,$3e,"E BACKLIGHT: ",DEC1 bl
   IF PORTE.0=%1 then
      IF bl=%1 THEN bl=%0
   endif
   if PORTE.1=%1 then
      IF bl=%0 THEN bl=%1
   ENDIF
   flag6=%0
ELSE
    lcdout $fe,$c0,$1,$0,"E BACKLIGHT: ",DEC1 bl
    IF flag6=%0 THEN write 7,bl:GOSUB blsub:flag6=%1
endif


' Reset all settings submenu
CASE 11
IF menu=%1 THEN
   IF flag7=%0 THEN
      rot=%1:write 0,rot           
      maxf=500:write 1,maxf.HIGHBYTE:write 2,maxf.LOWBYTE
      minf=10:write 3,minf.HIGHBYTE:write 4,minf.LOWBYTE                         
      imax=150:write 5,imax
      pwmf=3:write 6,pwmf:GOSUB pwmsub
      bl=%1:write 7,bl:GOSUB blsub
      Lcdout $fe,$c0,$3e,$3e,"F RESET? OK",REP $20\3:flag7=%1
   ENDIF
else
    IF menu=%0 THEN lcdout $fe,$c0,$20,$0,"F RESET?",REP $20\6:flag7=%0
endif


END SELECT


GOTO lp

It's working very well, the gain of speed of the loop is incredible (about ten times faster than the old program).

But sometimes, when I navigate into the menu, the LCD freeze and the PIC "resets". I don't know why. What's happen?

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