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psion/chatter #232, from psioncorp, 1649 chars, Aug  3 09:50 94
Comment to 221. 
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Here's two short procedures, one to return the current contrast setting 
and the other to increase or decrease the LCD contrast.

Dave (psioncorp)

/*  Routine to return the current LCD contrast setting  

    Author :  DP
    Started:  03/03/93

    The range of values returned is from 0 (lightest) to 15 (darkest)
*/


#define HardwareManager $008e
#define HwReadLcdContrast       $1300


PROC LcdCont:

        LOCAL ax%,bx%,cx%,dx%,si%,di%
        LOCAL flags%,err%
        LOCAL ret$(32)

        ax% = HwReadLcdContrast

        flags% = OS(HardwareManager,ADDR(ax%))

        IF flags% AND 1                         
                err% = ax% OR $ff00             
                PRINT ret$ = ERR$(err%)         
                GET           
        ELSE 
                ax% = ax% AND $000f     
                PRINT ax%               /*  Current contrast setting  */
                GET
        ENDIF
ENDP


/*  Prcedure to either darken or lighten the screen
    depending upon whether a +ve or -ve value is passed in ax%  

    Author:     DP
    Started:    03/03/93
*/


#define HardwareManager $008e
#define HwLcdContrastDelta      $1200


proc lcdIncr:

        LOCAL ax%,bx%,cx%,dx%,si%,di%
        LOCAL flags%,err%
        LOCAL ret$(32)

        ax% = HwLcdContrastDelta             /*  +ve, darker  */
rem     ax% = HwLcdContrastDelta  OR $0080   /*  -ve, lighter  */        

        flags% = OS(HardwareManager,ADDR(ax%))

        IF flags% AND 1                         
                err% = ax% OR $ff00             
                PRINT ret$ = ERR$(err%)         
                GET           
        ENDIF
ENDP