LED bar graph with selectable range min and max

DEFINE OSC 4
;----[USART Settings]-------------------------------------------------------
DEFINE HSER_RCSTA 90h    ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h    ' Enable transmit, BRGH=1
DEFINE HSER_SPBRG 25     ' 9600 Baud @ 4MHz, 0.16%
DEFINE HSER_CLROERR 1    ' Clear overflow automatically

;----[LCD Settings]---------------------------------------------------------
DEFINE LCD_DREG PORTA     ' LCD data port
DEFINE LCD_DBIT 4         ' LCD data starting bit 0 or 4
DEFINE LCD_RSREG PORTA    ' LCD register select port
DEFINE LCD_RSBIT 2        ' LCD register select bit
DEFINE LCD_EREG PORTA     ' LCD enable port
DEFINE LCD_EBIT 3         ' LCD enable bit
DEFINE LCD_BITS 4         ' LCD bus size 4 or 8
DEFINE LCD_LINES 2        ' Number lines on LCD
DEFINE LCD_COMMANDUS 2000 ' Command delay time in us
DEFINE LCD_DATAUS 50      ' Data delay time in us

;----[A/D Settings]---------------------------------------------------------
DEFINE ADC_BITS 10        ' ADCIN resolution  (Bits)
DEFINE ADC_CLOCK 1        ' ADC clock source  (Fosc/8)
DEFINE ADC_SAMPLEUS 11    ' ADC sampling time (uSec)

;----[Variables]------------------------------------------------------------
GraphMAX   VAR WORD
GraphMIN   VAR WORD
GraphVal   VAR WORD
X          VAR WORD
ADval      VAR WORD
Xmax       VAR WORD
Xmin       VAR WORD
char       VAR BYTE
OverRange  VAR BIT
UnderRange VAR BIT

;----[Aliases]--------------------------------------------------------------
RCIF       VAR PIR1.5
OverPin    VAR PORTC.5
UnderPin   VAR PORTC.4

;----[Default Values]-------------------------------------------------------
GraphMAX   = 100
GraphMIN   = 0
Xmax    = 100
Xmin      = 0

;----[Initialize]-----------------------------------------------------------
PORTB = 0
TRISB = 0
PORTD = 0
TRISD = 0
ANSEL = %00000001
ANSELH = 0
ADCON1.7 = 1
PAUSE 250 : LCDOUT $FE,1 : PAUSE 250 : LCDOUT $FE,1
GOSUB ShowMenu
GOSUB ShowLimits
OverRange = 0
UnderRange = 0

;----[Main Program Loop]----------------------------------------------------
Main:
    IF RCIF THEN GOSUB Terminal
    GOSUB GetAD
    GOSUB ShowGraph
    GOSUB CheckOverUnder
GOTO Main

;----[Get and Scale Analog Reading]-----------------------------------------
GetAD:
    ADCIN 0, ADval
    X = ADval * (Xmax - Xmin)
    X = DIV32 1023 + Xmin
    LCDOUT $FE,$80, "AD=",DEC ADval, "    "
    LCDOUT $FE,$8B, "X=",DEC X, "    "
RETURN

;----[Show the BarGraph]----------------------------------------------------
ShowGraph:
    IF X > GraphMAX THEN
        OverRange = 1
    ELSE
        OverRange = 0
    ENDIF
    IF X < GraphMIN THEN
        UnderRange = 1
    ELSE
        UnderRange = 0
    ENDIF
    X = (X MIN GraphMAX) MAX GraphMIN
    
    ;-- This is the formula being tested ---------------------
    GraphVal = $FFFF >> (16-(((X - GraphMIN) * 16) / (GraphMAX - GraphMIN)))
    
    PORTD = GraphVal & $FF
    PORTB = GraphVal >> 8
RETURN

;----[Show Menu for Terminal]-----------------------------------------------
ShowMenu:
    HSEROUT ["MENU: 1=GraphMAX, 2=GraphMIN, 3=Xmax, 4=Xmin :"]
RETURN

;----[Handle the RS232 Terminal]--------------------------------------------
Terminal:
    HSERIN [char]
    SELECT CASE char
      CASE "1" : HSEROUT [13,10,"Enter the GraphMAX: "]
                 HSERIN  [DEC GraphMAX]
      CASE "2" : HSEROUT [13,10,"Enter the GraphMIN: "]
                 HSERIN  [DEC GraphMIN]
      CASE "3" : HSEROUT [13,10,"Enter the Xmax: "]
                 HSERIN  [DEC Xmax]
      CASE "4" : HSEROUT [13,10,"Enter the Xmin: "]
                 HSERIN  [DEC Xmin]
      CASE ELSE : HSEROUT [7]
    END SELECT

;----[Show Limits]----------------------------------------------------------
ShowLimits:
    LCDOUT $FE,$C0,"    GRAPH    X      "
    LCDOUT $FE,$94,"MAX:                "
    LCDOUT $FE,$D4,"MIN:                "
    LCDOUT $FE,$99,DEC GraphMAX
    LCDOUT $FE,$D9,DEC GraphMIN
    LCDOUT $FE,$A1,DEC Xmax
    LCDOUT $FE,$E1,DEC Xmin

RETURN

;----[Look for Over and Under Range]----------------------------------------
BlinkSpeed  CON 50
BlinkCount  VAR WORD

CheckOverUnder:
    BlinkCount = BlinkCount + 1
    IF BlinkCount = BlinkSpeed THEN
        BlinkCount = 0
        IF OverRange THEN
            TOGGLE OverPin
        ELSE
            LOW OverPin
        ENDIF
        IF UnderRange THEN
            TOGGLE UnderPin
        ELSE
            LOW UnderPin
        ENDIF
    ENDIF
RETURN