# ADC to LED problem MC68HC12

Discussion created by Al Delgado on Oct 6, 2011
Latest reply on Oct 6, 2011 by Allen Babb

I have code that is not working for the MC68HC12, it takes 0-5V into the
ADC and does some math to convert to revolutions per second and outputs
to 2 LED's. Could someone analyze the code to tell me in general what
might be wrong with the code. Some where I've think I've made a basic
mistake, I have not used the ADC before. I get not display on LED's.

The code is also attached.

`        include 'MC9S12C128.inc'                org     \$800          movb    #\$FF, DDRB          movb    #\$C0, ATDCTL2          movb    #\$00, ATDCTL3          movb    #\$00, ATDCTL4          ldaa    #1Wait      deca           bne     Wait          movb    #\$20, ATDCTL5          ldab    ATDDR0H           ;AB will hold the input          loop      clra                    ;clear AA- AB holds converted input          ldab    #\$80            ;test data -to be commented out          ldx     #51             ;relationship between digital number and BCD                   idiv                    ;as defined in prelab          stx     holder          ;holder holds the ones place          ldaa     #10            ;there will be a remainder. Want at least 1 decimal point accuracy          mul          ldx     #51             ;repeat dividing by 51          idiv              stx     holder2         ;holder2 holds the tenths place                                               ldd     holder          ;what follows is multiplying both the ones and teneths place by (18/5)          ldy     #18             ;as shown in pre-lab work          emul          std     holder          ldd     holder2          ldy     #18          emul          std     holder2          ldd     holder          ldx     #5          idiv          stx     holder          ldd     holder2          ldx     #5          idiv          stx     holder2          ldd     holder2         ;we then want to divide holder2 (tenths place) by 10 and add it to holder          ldx     #10             ;in order to get 1 number with which to continue calculation of RSP          idiv          xgdx          addd    holder          std     Va          ldd     #14             ;we want to add 1.4 to Va, per pre-lab work. divide 14 by 10 to achieve this          ldx     #10          idiv          stx     holder          std     holder2          ;remainder stored in holder2          ldd     Va          addd    holder          std     Va          ldd     holder2          ldx     #10          idiv          ldd     Va          addd    0,x          std     Va          ldy     #2                ;multiply by 2          emul              std     Va          ldd     #46               ;multiply by .46 = (46/100)          ldx     #100          idiv          stx     Va                 ;Va now contains RPS                    ldd     Va          cpd    #10          bge     output1          ldaa    #00           output1   ldd     Va                ;checks value of tens place of RPS          ldx     #10          idiv          stx     tensplace          ldd     tensplace          cpd     #1          beq     one1          ldd     tensplace          cpd     #2          beq     two1          ldd     tensplace          cpd     #3          beq     three1          ldd     tensplace          cpd     #4          beq     four1          ldd     tensplace          cpd     #5          beq     five1          ldd     tensplace          cpd     #6          beq     six1          ldd     tensplace          cpd     #7          beq     seven1          ldd     tensplace          cpd     #8          beq     eight1          ldd     tensplace          beq     nine1          ldaa    #00          one1      ldaa    one           ;will load appropriate hex number to have 7-seg display output two1      ldaa    two           ;appropriate numberthree1    ldaa    threefour1     ldaa    fourfive1     ldaa    fivesix1      ldaa    sixseven1    ldaa    seveneight1    ldaa    eightnine1     ldaa    nine            staa    tensplace                    ldd     Va                ;checks value of tens place of RPS          ldx     #10          idiv          stx     onesplace          ldd     onesplace          cpd     #1          beq     one2          ldd     onesplace          cpd     #2          beq     two2          ldd     onesplace          cpd     #3          beq     three2          ldd     onesplace          cpd     #4          beq     four2          ldd     onesplace          cpd     #5          beq     five2          ldd     onesplace          cpd     #6          beq     six2          ldd     onesplace          cpd     #7          beq     seven2          ldd     onesplace          cpd     #8          beq     eight2          ldd     onesplace          beq     nine1          ldaa    #00          one2      ldaa    one           ;will load appropriate hex number to have 7-seg display output two2      ldaa    two           ;appropriate numberthree2    ldaa    threefour2     ldaa    fourfive2     ldaa    fivesix2      ldaa    sixseven2    ldaa    seveneight2    ldaa    eightnine2     ldaa    nine            staa    onesplace                              movb    #\$7C, DDRCAN   ;configure portcan for output (from textbook)          movb    #\$FF, DDRP    ;configure portp for output          movb    tensplace, PORTP   ;place tens-place output code on portp          movb    #\$40, PORTCAN       ;activate pcan6 so that led will illuminate with tensplace digit          movb    #\$30, PORTCAN       ;activate pcan5          movb    onesplace, PORTP    ;illuminate ones-place output code          lbra     loop                    swiholder    rmb     2 holder2   rmb     2Va        rmb     2tensplace rmb     1onesplace rmb     1zero      equ     \$7Eone       equ     \$30two       equ     \$6Dthree     equ     \$79four      equ     \$33five      equ     \$5Bsix       equ     \$5Fseven     equ     \$70eight     equ     \$7Fnine      equ     \$7B PORTP     equ     \$56PORTCAN   equ     \$13E DDRCAN    equ     \$13F                                              `