CET335 Microprocessor Interfacing Lab 4: Digital Output

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1 CET335 Miroprossor Intrfaing La 4: Digital Output Introdution: As with digital inputs, digital outputs ar also asy to intrfa to and ontrol from softwar. This la dmonstrats hardwar and softwar rquirmnts for simpl digital output intrfaing to a varity of digital output dvis. Matrials ndd: 220Ω ¼ W rsistor (8) 330Ω ¼ W rsistors or 330Ωx8 DIP rsistor 330Ωx8 SIP rsistor 1kΩ ¼ W rsistor 1N4001 diod 2N2222 NPN ipolar transistor LED LED ar graph display LED 7-sgmnt numri display (CC or CA) indiator lamp 5VDC DIP rlay spakr osillosop, Ohmmtr, powr supply I. LEDs 1. Build th LED iruit as shown in figur 1 on th EVB radoard. Osrv propr polarity of th LED. Rviw a digital txt or a w rsour ( if nssary. Q1. Dos this iruit rquir a positiv tru or ngativ tru logi output? V Ω Fig. 1: LED iruit 2. Sin this iruit rquirs to an output port, w ar now onrnd with DDRB7, th Data Dirtion Rgistr it for. Rfr to th MC9S12DT256 Dvi Usr Guid to omplt th following statmnts. Q2. PORTB rsids at, DDRB rsids at. 3. From th EVB monitor prompt, opn DDRB s addrss with th mmory modify (MM) ommand. Q3. What is th dfault valu of DDRB7? This sts its rsptiv lin to an. Q4. For its rsptiv I/O pin to an output, a DDR it must st to. 4. Mak an output y hanging DDRB appropriatly, i.. lav th othr 7 its st as inputs. Bwar of sid ffts to othr its!!! Noti th fft on your LED. 5. Opn PORTB s addrss and dtrmin why th LED is now on or off. Chang s valu and vrify propr ontrol of your LED iruit. Q5. must a to turn th LED on and to turn th LED off. Is this onsistnt with ngativ-tru logi? 6. Now it s tim for som ool softwar. Hav you vr notid th powr LED on a modrn Maintosh PC whil in standy and wondr how it dos that? It slowly fads rightr and dimmr to indiat th standy mod. Wait a minut: LEDs ar digital dvis! Thy ar ithr on or off; thr s no suh thing as an LED half way on. Lt s try to onfirm this. Otain/rat th program DOdmo.asm as shown in listing 1. Assml and download this program to th EVB. Exut th program and osrv its output on th LED. Viw th output on an osillosop st for 2V pr division vrtial and 5 ms pr division horizontal. Doumnt your findings in your la notook, inluding your answrs to th following qustions. Q6. Dsri th fft of this program on th LED. La 4: Digital Output - Pag 1

2 Q7. Basd on th sop display, is th output priodi or apriodi? If priodi, what is its frquny? Q8. Is th output onstant or varial amplitud (whn on)? If onstant, what is its voltag lvl? Q9. How would you dsri th output signal s duty yl and th rsulting fft on th LED? Q10. What hang(s) to DOdmo would rquird to hang th frquny to 40 Hz? Mak this hang and vrify on th sop. Thus, as you hav sn, it is possil to light an LED half way with rspt to tim instad of voltag. Rviw th osillosop wavform display again you hav just n introdud to somthing alld puls-width modulation. W will s mor of this latr in th ours. II. LED Bargraphs 7. Build th LED argraph iruit as shown in figur 2 on th DRAGON12 radoard. Th LED argraph will hav all athods on on sid and all anods on th opposit sid in a fd thru onfiguration. If you annot idntify th argraph s polarity y insption, us a ground pro and urrnt-limitd V pro (via a 330Ω rsistor) to dtrmin th polarity xprimntally. Th SIP ommon pin of th rsistor ntwork will idntifid on th pakag, usually with a strip. Not that th argraph will proaly hav 10 LEDs, w us only 8 of thm hr. V PB0 LED Bar Display 330Ω 10-pin SIP Fig. 2: LED argraph iruit 8. Modify th S12 s DDRB y making all 8 its outputs. Th DDR valu to ahiv this is $. 9. Opn PORTB s addrss with th MM ommand. Chang PORTB s valu to various hx pattrns and vrify propr display output. Again, us of th / option to th MM ommand is usful hr. For ah of th following valus, prdit th output for you try it: $00, $FF, $55 and $AA. Q11. If snt to PORTB, what would an inrasing inary ount squn from 0 to $FF display as on th argraph? 10. Tim for som ool softwar again. Otain/rat th program BarGraph.asm as shown in listing 2. Assml and download this program to th EVB. Exut th program and osrv its output on th argraph. Try diffrnt DTIME valus inluding 50. Doumnt your findings in your la notook. Q12. Explain how this xampl program works and omplt th missing two?? ommnts. (Don t spnd mor than a oupl minuts on this for moving on this is an advand thniqu th instrutor an xplain latr.) 11. Rmov your LED argraph iruit. 12. Th DRAGON12 EVB also faturs on-oard display apaility via 8 LEDs on port B as wll as th sgmnts of th 4-digit numri display. You may hav notid th dimal points on th 4-digit display also turnd on in th prvious stps. Th on-oard LEDs ar nald y outputting a low on PJ1. Sin PJ1 is alrady a 0, all you nd to do is to mak PJ1 an output y stting it 1 of DDRJ La 4: Digital Output - Pag 2

3 $26A) to a 1. Do this now y stting DDRJ to with th mmory modify ommand. Also turn off all 4 digits of th numri display y stting DDRP (@ $25A) to $0F. Run BarGraph again; you should noti th on-oard LEDs now sanning ut with invrtd logi. Baus th on-oard LEDs us positiv logi on port B, doumnt in you la notook what hangs would nd to mad to BarGraph.asm to work as it did with your uilt iruit. III. LED Numri Displays 13. Build th LED numri display iruit as shown in figur 3 on th EVB radoard. You may dtrmin th display s pinout xprimntally as you may hav don in your digital ours: a. Choos a pin and onnt it to +5V (for CA) or ground (for CC).. Us a 330 rsistor (DIP styl) onntd to ground (for CA) or +5V (for CC) as a pro and tst all othr pins to s if you an light a sgmnt.. If no sgmnt lights, mov th fixd onntion of stp (a) to anothr pin and rpat stp (). Whn a sgmnt lights, you hav found th orrt fixd onntion. d. On you hav found th orrt ommon pin, lav it alon and us th rsistor pro to find whih pins ontrol ah of th a,,, d,, f, g and dimal point sgmnts. Doumnt your findings in your la notook. dp g a CA V PB0 f d a f g d CC or! 330Ωx7 LED Numri Display Fig. 3: LED numri display iruit 14. From th EVB monitor prompt, mak PORTB all outputs y stting DDRB to $FF. Chang PORTB s valu to various hx pattrns and vrify propr display output. Try to rat oth lgil numri digits and som hiroglyphis. Complt th hxadimal to svn-sgmnt pattrn tal low as appropriat for th display you ar using. digit \ sgs g f d a hx A C d E F La 4: Digital Output - Pag 3

15. Otain/rat th program LEDount.asm as shown in listing 3. Assml and download this program to th EVB. Exut th program and osrv its output on th numri display.

4 15. Otain/rat th program LEDount.asm as shown in listing 3. Assml and download this program to th EVB. Exut th program and osrv its output on th numri display. Fix th program and rrun until orrt rsults ar ahivd. Doumnt your findings in your la notook. Q13. Explain what hang(s) to this program would rquird to swith th display to th opposit polarity. 16. As prviously mntiond, th DRAGON12 EVB faturs 4 on-oard numri LED displays. This stp will xris our LEDount program on th lft-most (digit 3) display. Rmov your uilt LED display iruit. Mak th following modifiation to LEDount and run on th EVB: hang mov #$0F,DDRP to mov #$0E,DDRP Doumnt in your la notook any prolms nountrd and what orrtiv masurs wr ndd. IV. Transistor Drivrs 17. Rst th EVB. Connt th indiator lamp twn and V as shown in figur 4. V Fig. 4: Indiator lamp iruit 18. Mak an output as in stp 4 thn hang output twn low and high. You should noti that th lamp will not light. Rmov th lamp now (quikly). Q14. Why wont th lamp light? Bfor you rspond it s urnd out! lt s s what th Grman physiist Gorg Ohm said aout this in 1827 a. Using an Ohmmtr, masur and rord th sris rsistan of th indiator lamp: Ω Not that if you hav any rsistan at all, th lamp is not urnd out.. Using Ohm s law I = V/R, th lamp urrnt would V lamp /R lamp or 5V/ Ω = ma.. What is th urrnt drain pr pin sp (I D ) from th 9S12 Dvi Guid, pag 91? ma. AhA that s why you wr instrutd to quikly rmov th lamp aov! 19. As you larnd in th prvious stp, output pins in gnral just arn t vry powrful. What w nd hr is mor powr! Ronfigur your iruit to that in figur 5 y adding a ipolar NPN transistor drivr. For a 2N2222 transistor in a TO-92 pakag, th pins ar mittr / as / olltor lft-to-right looking at th flat. Us V from th EVB for V+. V+ 1kΩ 2N2222 Fig. 5: Lamp iruit with drivr Fig. 6: TO-92 pakag 20. Rpat th monitor ommands of stp 18 and vrify that th lamp now works. Th 2N2222 is a vry popular NPN transistor that an swith iruits up to 1 Amp! Its omplmntary PNP ousin is th 2N Rrun DOdmo from stion 1 on this lamp iruit. You should noti th lamp fading rightr and dimmr ut without muh ovrall intnsity aus of th thrmal dlays in th lamp s filamnt. On way to improv this is y oprating it hottr. Anothr auty of a transistor drivr is that it an swith dvis oprating on muh highr V+ lvls. Disonnt th lamp from th EVB s V ( vry sur of this!!) and onnt th lamp to an xtrnal powr supply instad. Don t forgt to also hook th La 4: Digital Output - Pag 4

5 powr supply ground to th radoard/evb ground. Vary th powr supply twn 5V and a maximum of 12V (do not xd!). Doumnt your findings in your la notook. Powr off and disonnt th powr supply. 22. Rpla th lamp with th LED iruit of figur 1. It should now look lik figur 7. With DOdmo running, you should noti th LED has gaind ovrall intnsity ompard to stion 1 whr it was onntd dirtly to th output port. Th transistor is now arrying all th LED urrnt and th load on has n rdud from som 20 ma to lss th 5 ma. is happir, th LED is happir, and you should too! V 1kΩ - + 2N Ω Fig. 7: LED with drivr 23. W will now add a 5VDC DIP rlay to th iruit. But first, lt s profil th rlay. a. Masur and rord th sris rsistan of rlay oil: R rlay = Ω. Th oprating voltag of th rlay, V rlay, will 5V minus th V drop of th transistor whn in its on stat. Typial ipolar transistors ar aout 0.6V. Thus V rlay = V.. Applying Ohm s law on again: I rlay = V rlay /R rlay = ma. As you an s, th rlay is also too muh load for a dirt onntion to a port pin; howvr, th transistor an still asily driv oth th rlay and th LED simultanously. 24. Rst th EVB. Add a 5VDC DIP rlay and th 1N4001 snur diod in paralll to th LED/rsistor as shown in figur 8. Th purpos of this diod is to fftivly dump into V th indutiv kikak from th oil ausd whn its magnti fild ollapss. Although vry rif, this kikak an asily xd 100 volts! B sur to osrv propr polarity of th rlay oil. 220Ω V 1kΩ 2N2222 Fig. 8: Rlay with LED indiator - + 1N N.O. N.C. N.O. N.C. V 1kΩ Fig. 9: Spakr drivr 25. Using appropriat monitor ommands again as in stp 18, vrify that you an oprat oth th rlay and LED from th output. You should al to asily har th rlay lik whn it ngags and rlass. Not that th normally-opn and normally-losd rlay ontats an usd to swith rathr larg loads up to th ontat ratings. This ould asily 120VAC and 10 Amps! 26. Although rlays ar not dsignd for ontinuous rapid opration, w an rifly tst th ffts of yling th rlay at 50 Hz with varying duty yl. Run DOdmo on your urrnt iruit. Giv yourslf a pat on th ak as you v just givn irth to a digital rikt! Trivia fat: did you know that you an prdit th amint tmpratur from a ommon US rikt? Just add 40 to th numr hirps it produs in 15 sonds. La 4: Digital Output - Pag 5

6 27. For tru audio output, our transistor drivr may also usd to driv a ommon spakr as shown in figur 9. If a spakr is availal, ronfigur your iruit as shown and run DOdmo. 28. Also availal on th DRAGON12 EVB is a form C doul-pol doul-throw (DPDT) rlay just aov th kypad. Th rlay drivr iruit, also a 2N2222, is onntd to th S12 s PE2 pin. Port E livs at mmory loation whil its orrsponding DDRE livs at. Using th monitor s mmory modify ommand, mak PE2 an output thn tst ontrol of th rlay y hanging valus of PE2. Not that you may gt th Can t writ targt mmory rror mssag ut that s aus othr port E pins ar inputs and your writtn valu is not mathing thos its. You should still har th rlay lik on and off as wll as s th rlay LED turn on and off. 29. Rmov any iruit rmaining on th radoard. Modify a opy of DOdmo.asm to output th ontrol puls on PE2 instad of. Doumnt your hangs in your la notook. Run your modifid vrsion and vrify y haring th rlay and wathing th rlay LED. Instrutor Signoff: La 4: Digital Output - Pag 6

7 Listing 1: Digital output xampl program * Projt nam: CET335 Digital Output xampl * Fil nam: DOdmo.asm * Author(s): jss * Dat: 18-Sp-2011, mods to run on DRAGON12 * Dsription: This program dmonstrats digital output ontrol y * produing an inrasing/drasing duty yl (D.C.) * output puls on. Also shown is th us of it * manipulation instrutions (BSET/BCLR). * <<< EQUATE SECTION >>> ; onstants CR EQU $0D ;ASCII Carriag Rturn PERIOD EQU 20 ;priod of output puls in ms. ; mmory map dfinitions DATA EQU $1000 ;whr our data an gin on EVB CODE EQU $2000 ;whr our od an gin on EVB ; "systm" ojts (I/O rgistrs, monitor routins, t.) PORTB EQU $0001 ;I/O Port B DDRB EQU $0003 ;DDR for port B SCI0SR EQU $00CC ;SCI0 Status Rg., 5=RDRF ; D-Bug12 utility routin vtors VPUTCHAR EQU $EE86 ;snd haratr in B to output dvi ****************************************************************** ****************************************************************** * <<< DATA SECTION >>> ; varial data alloations (RMB)... ORG DATA ****************************************************************** * <<< MAIN PROGRAM LOOP >>> * Infinitly loop outputting a varial D.C. puls on. * Kyoard input stops program. ORG CODE START ldx #Msg1 ;point X to grting mssag jsr PUTS ;output it st DDRB,$80 ; is now an output lra ;start at 0 ms on Loop1 jsr Puls ;output 1 puls ina ;ump on-tim ountr mpa #PERIOD ;up to 100% yt? n Loop1 ;if not Loop2 jsr Puls ;output 1 puls da ;d on-tim ountr n Loop2 ;rpat until 0 CkBoard rlr SCI0SR,$20,Loop1 ;ontinu until RDRF swi ;ls nd program Puls psha ;sav rgistrs usd hr psh ta ;opy dlay tim to B q NoPuls ;0ms = no puls st PORTB,$80 ;st output port high jsr DlayN ;hold for on-tim NoPuls lr PORTB,$80 ;rturn output port low ldaa #PERIOD ;off tim = PERIOD - on tim sa q PlsExit ;skip dlay if 0 jsr DlayN ;hold for off-tim PlsExit pul ;rstor rgistrs pula * DlayN: dlay 'N' millisonds * in: A = 'N', numr of ms to dlay * out: A = 0, all othr rgistrs not afftd DlayN sr Dlay1 ;go dlay 1 millisond dn A,DlayN ;d 'N' & ontinu till zro * Dlay1: dlay 1 millisond via softwar, * assums F=24 MHz (and no intrrupts) La 4: Digital Output - Pag 7

8 * all rgistrs prsrvd for allr Dlay1 pshx ;2~ prsrv rgistrs usd hr ldx #7996 ;2~ itrations for 1ms. dn X,* ;3~ 7996 loops * 3~/loop = 23988~ ;3~ rovr usd rgistrs ;5~ = 24000~ = 1ms. * string output routin, X points to null-trminatd string PUTS lda 0,X ;gt 1 har from string q PSDONE ;don if trminating null jsr PUTCHAR ;output this har inx ;advan X to nxt har ra PUTS ;ontinu PSDONE ;don, rturn to allr * singl haratr (in B) output routin PUTCHAR pshx ;sav allr's X ldx VPUTCHAR ;fth addrss of monitor rtn jsr 0,X ;all monitor rtn. ;rstor allr's X * Constant Data Msg1 FCC "Digital output tst..." FCB CR FCC "(prss any ky to xit program)" FCB CR,0 END Listing 2: Bargraph display xampl program * Projt nam: CET335 argraph display xampl * Fil nam: BarGraph.asm * Author(s): jss * Dat: 22-Sp-2011, modifid to run on DRAGON12 oard * Dsription: This program dmonstrats 8-it digital output y * sanning a "Knight Ridr" pattrn to an LED argraph * display on PORTB. A vry slik ut vry dangrous * oding trik is usd - s if you an omplt th * two '??' ommnts! * <<< EQUATE SECTION >>> ; onstants CR EQU $0D ;ASCII Carriag Rturn DTIME EQU 200 ;san dlay tim in ms ; mmory map dfinitions DATA EQU $1000 ;whr our data an gin on EVB CODE EQU $2000 ;whr our od an gin on EVB ; "systm" ojts (I/O rgistrs, monitor routins, t.) PORTB EQU $0001 ;I/O port B DDRB EQU $0003 ;DDR for port B SCI0SR EQU $00CC ;SCI0 Status Rg., 5=RDRF ; D-Bug12 utility routin vtors VPUTCHAR EQU $EE86 ;snd haratr in B to output dvi * <<< MAIN PROGRAM LOOP >>> * Continuously loop whil sanning a argraph display on PORTB. * Kyoard input stops program. ORG CODE START ldx #Msg1 ;point X to grting mssag jsr PUTS ;output it mov #$FF,DDRB ;mak port B all outputs lda #$FF ;start w/ B=all 1's l ;and C flag lar SCAN rol ;mov 0 to nxt it sta PORTB ;output to port B ldaa #DTIME ;dlay tim sr DlayN ;(C is unafftd) s SCAN ;san all its of port B ldaa SCAN ;swith rotat dirtion La 4: Digital Output - Pag 8

9 ora #$03 ;?? staa SCAN ;?? CkBoard rlr SCI0SR,$20,SCAN ;ontinu until RDRF swi ;nd program * DlayN: dlay 'N' millisonds * in: A = 'N', numr of ms to dlay * out: A = 0, all othr rgistrs not afftd DlayN sr Dlay1 ;go dlay 1 millisond dn A,DlayN ;d 'N' & ontinu till zro * Dlay1: dlay 1 millisond via softwar, * assums F=24 MHz (and no intrrupts) * all rgistrs prsrvd for allr Dlay1 pshx ;2~ prsrv rgistrs usd hr ldx #7996 ;2~ itrations for 1ms. dn X,* ;3~ 7996 loops * 3~/loop = 23988~ ;3~ rovr usd rgistrs ;5~ = 24000~ = 1ms. * string output routin, X points to null-trminatd string PUTS lda 0,x ;gt 1 har from string q PSDONE ;don if trminating null jsr PUTCHAR ;output this har inx ;advan X to nxt har ra PUTS ;ontinu PSDONE ;don, rturn to allr * singl haratr (in B) output routin PUTCHAR pshx ;sav allr's X ldx VPUTCHAR ;fth addrss of monitor rtn jsr 0,X ;all monitor rtn. ;rstor allr's X * Constant Data Msg1 FCC "Bargraph display tst..." FCB CR FCC "(prss any ky to xit program)" FCB CR,0 END Listing 3: Numri display xampl program * Projt nam: CET335 numri display xampl * Fil nam: LEDount.asm * Author(s): jss * Dat: 22-Sp-2011, modifid to run on DRAGON12 oard * Dsription: This program dmonstrats ontrol of a 7-sgmnt LED * numri display. Not that th 7-sgmnt lookup tal * (SSTBL) is wrong and nds fixd! * <<< EQUATE SECTION >>> ; onstants CR EQU $0D ;ASCII Carriag Rturn DTIME EQU 500 ;digit dlay tim in ms ; mmory map dfinitions DATA EQU $1000 ;whr our data an gin on EVB CODE EQU $2000 ;whr our od an gin on EVB ; "systm" ojts (I/O rgistrs, monitor routins, t.) PORTB EQU $0001 ;I/O Port B DDRB EQU $0003 ;DDR for port B PTP EQU $0258 ;I/O port P DDRP EQU $025A ;DDR for port P SCI0SR EQU $00CC ;SCI0 Status Rg., 5=RDRF ; D-Bug12 utility routin vtors VPUTCHAR EQU $EE86 ;snd haratr in B to output dvi * <<< MAIN PROGRAM LOOP >>> La 4: Digital Output - Pag 9

10 * Count 0..F on th LED numri display with a dlay twn ah digit. ORG CODE START ldx #Msg1 ;point X to grting mssag jsr PUTS ;output it mov #$0F,DDRP ;turn off all 4 on-oard digits mov #$FF,DDRB ;mak port B all outputs lr ;start ount at 0 Loop jsr OutHx ;all display output rtn ldx #DTIME jsr DlayN ;hold digit for a whil in ;advan to nxt digit mp #16 ;don yt? n Loop ;if not swi ;rturn to monitor * OutHx: lookup 7-sgmnt pattrn for hx digit and output to PORTB * in: B = hx digit 0..F to display * out: nothing, rgistrs A & X dstroyd OutHx ldx #SSTBL ;point X to 7-sgmnt tal ldaa B,X ;fth mathing 7-sgmnt pattrn staa PORTB ;snd to display * DlayN: dlay 'N' millisonds * in: X = 'N', numr of ms to dlay * out: X = 0, all othr rgistrs not afftd DlayN sr Dlay1 ;go dlay 1 millisond dn X,DlayN ;d 'N' & ontinu till zro * Dlay1: dlay 1 millisond via softwar, * assums F=24 MHz (and no intrrupts) * all rgistrs prsrvd for allr Dlay1 pshx ;2~ prsrv rgistrs usd hr ldx #7996 ;2~ itrations for 1ms. dn X,* ;3~ 7996 loops * 3~/loop = 23988~ ;3~ rovr usd rgistrs ;5~ = 24000~ = 1ms. * string output routin, X points to null-trminatd string PUTS lda 0,x ;gt 1 har from string q PSDONE ;don if trminating null jsr PUTCHAR ;output this har inx ;advan X to nxt har ra PUTS ;ontinu PSDONE ;don, rturn to allr * singl haratr (in B) output routin PUTCHAR pshx ;sav allr's X ldx VPUTCHAR ;fth addrss of monitor rtn jsr 0,X ;all monitor rtn. ;rstor allr's X * Constant Data Msg1 FCC "Numri display tst..." FCB CR,0 SSTBL FCB $00,$01,$02,$03,$04,$05,$06,$07,$08,$09,$0A,$0B,$0C,$0D,$0E,$0F END La 4: Digital Output - Pag 10

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