New Micros, Inc - Pulse Width Modulation with HC11

rob

08-03-00, 12:49 PM

PWM on the 68HC11 is a pain since you have to use interrupts to make it work. Here is a chunk of code used to control eight different joints on a robot with 8 PWM channels. The interrupt just outputs the bytes from the legs array. Different joints are activated by setting bits within the array with SET-BITS and CLEAR-BITS. This is more then you probably need but it is good for multiple PWM outputs. (I've removed the code that deals with input sensors.) RobCOLD ( remove all previous software( Four limb crabot controller Rob Chapman Apr 11, 1999 )HEX ( 7F00 S0 ! SP! ( increase data stack size ( 7E00 R0 ! QUIT ( increase return stack size( ==== Timer control registers ==== ) B023 CONSTANT TFLG1 ( timer interrupt flag register 1 B025 CONSTANT TFLG2 ( timer interrupt flag register 2 B021 CONSTANT TCTL2 ( timer control register 2 B020 CONSTANT TCTL1 ( timer control register 1 B010 CONSTANT TIC1 ( timer input capture register 1 B012 CONSTANT TIC2 ( timer input capture register 2 B01E CONSTANT TOC5 ( timer output capture register 5 B026 CONSTANT PACTL ( port A control register B009 CONSTANT DDRD ( port D data direction register B022 CONSTANT TMSK1 ( timer interrupt mask1( ==== Leg states array ==== ) VARIABLE legs.out ( points to state output VARIABLE legs.end ( points to last legs state CREATE legs 200 ALLOT ( 256 possible states of A and D outputs HERE 2 - legs.end ! legs legs.out ! ( set pointer and limit( Map indices to state table and limit them : >LEGS ( i \ j -- a \ b ) 2 0 DO 0 MAX FF MIN 2* legs + SWAP LOOP ;( ==== Tools ==== ) : C@+ ( a -- c \ a+ ) COUNT SWAP ; : C!+ ( c \ a -- a+ ) SWAP OVER C! 1 + ;( Bits in the state output array are two bytes. The bytes are the same ( but the second byte is shifted left by two. The first byte is used to ( output to the A port and the second byte is used to output to the D port. ( Each port uses a nibble. : SET-BITS ( start \ end \ mask -- ) >R SWAP >LEGS BEGIN DUP C@ R@ OR SWAP C!+ DUP C@ R@ 2* 2* OR SWAP C!+ 2DUP U< UNTIL 2DROP R> DROP ; : CLEAR-BITS ( start \ end \ mask -- ) NOT >R SWAP >LEGS BEGIN DUP C@ R@ AND SWAP C!+ DUP C@ R@ 2* 2* AND SWAP C!+ 2DUP U< UNTIL 2DROP R> DROP ;( ==== 68HC11 deployment ==== ) ( port A bits 4,5,6,7 and port D bits 2,3,4,5 are used to ( drive eight actuators( Binding of joint actuators to port bits: usage: 20 RRO 45 RRI ) : JOINT ( bit-mask -- ) <BUILDS 0 C, C, ( bend -- ) DOES> 2DUP C@+ C@ >R 2DUP < IF R> CLEAR-BITS ELSE SWAP R> SET-BITS THEN C! ;( ==== Separate joints ==== ) 80 JOINT RRI ( rear right inner 40 JOINT RLO ( rear left outer 20 JOINT FLO ( front left outer 10 JOINT RLI ( rear left inner 8 JOINT FRI ( front right inner 4 JOINT RRO ( rear right outer 2 JOINT FRO ( front right outer 1 JOINT FLI ( front left inner( ==== Leg macros ==== ) : RR ( n -- ) DUP RRI RRO ; : RL ( n -- ) DUP RLI RLO ; : FR ( n -- ) DUP FRI FRO ; : FL ( n -- ) DUP FLI FLO ; : ALL ( n -- ) DUP RR DUP RL DUP FR FL ;( ==== Assembler branching ==== ) : fwd HERE 0 C, ; : fwd: HERE OVER - 1 - SWAP C! ;( ==== Output ports to actuators ==== ) B000 CONSTANT portA B008 CONSTANT portD( ==== PWM parameters ==== ) VARIABLE TIME 200 TIME ! ( length of of periodCODE SIR-PWM ( servicing interrupt routine for time to next transition ) ( each time a wraparound counter is the same as a count, this interrupt ) ( routine is called. It revises the count and acknowledges the interrupt ) FE C, legs.out , ( ldx legs.out ; get state output pointer EC C, 0 C, ( ldd 0,x ; state outputs BC C, legs.end , ( cpx legs.end ; compare to state array end 27 C, fwd ( beq fwd ; same so reset 08 C, 08 C, ( inx inx ; next state output 20 C, fwd ( bra fwd ; continue later SWAP fwd: CE C, legs , ( ldx #legs ; first state output fwd: FF C, legs.out , ( stx legs.out ; update state output pointer CE C, B000 , ( LDX #$B000 : base address of registers A7 C, portA C, ( staa portA,X ; upper quad E7 C, portD C, ( stab portD,X ; lower quad 1D C, TFLG1 C, F7 C, ( BCLR TFLG1,X $F7 : clear interrupt flag FC C, TIME , ( LDD TIME : half period time ) E3 C, TOC5 C, ( ADDD TOC5,X : add the current transition time ) ED C, TOC5 C, ( STD TOC5,X : and store it back for next time ) 3B C, ( RTI : return to normal processing ) END-CODECODE-SUB +INT 0E C, 39 C, END-CODE ( enable interrupts ) CODE-SUB -INT 0F C, 39 C, END-CODE ( disable interrupts ): COLD -INT COLD ; ( redefine cold to turn off interrupts )( ==== Actuator control ==== ) : OFF TCTL1 C@ 3 NOT AND TCTL1 C! 0 ALL 0 portA C! 0 portD C! ; ( turn off the signal ): ON ( turn on the signal ) 0 ALL ( all legs are at zero legs 200 ERASE ( all state outputs to zero 0 portA C! 0 portD C! ( all outputs to zero PACTL C@ 80 OR PACTL C! ( ddrA7 is an output 3C DDRD C! ( ddrD2-5 are outputs -INT ['] SIR-PWM @ 100 /MOD 7E B7CE EEC! ( jmpe opcode ) B7CF EEC! B7D0 EEC! ( install sir ) 01 TCTL1 C! ( toggle output ) 08 TMSK1 C! ( enable 1 interrupt ) +INT ;

MLCarter

08-27-00, 05:17 PM

Here is code I have come up with to regulate power flow to a battery bank. You can change the % time set with the ratio of INC1:(INC1+INC2) HEX: IS CONSTANT ;B000 IS PORTA B020 IS TCTL1 B022 IS TMSK1 B023 IS TFLG1 B01E IS TOC51002 IS INC1 1004 IS INC22000 INC1 ! ( time set 1000 INC2 ! ( time clearCODE SIR-PWM B6 C, PORTA , ( LDAA porta 85 C, 8 C, ( BITA test PA3 set 27 C, B C, ( BEQ branch if set, 11 locs forward FC C, INC1 , ( LDDA inc1, time PA3 set F3 C, TOC5 , ( ADDD add to TOC5 FD C, TOC5 , ( STDA back into TOC5 20 C, 9 C, ( BRA branch 9 locs forwardFC C, INC2 , ( LDDA inc2, time PA3 cleared F3 C, TOC5 , ( ADDD add to TOC5 ) FD C, TOC5 , ( STDA TOC5 )86 C, 08 C, ( LDAA #08 $08 to clear bit B7 C, TFLG1 , ( STAA store at TFLG1 3B C, ( RTI return from interupt) END-CODECODE-SUB +INT 0E C, 39 C, END-CODE CODE-SUB -INT 0F C, 39 C, END-CODE: ON -INT ['] SIR-PWM @ 100 /MOD 7E B7CE EEC! B7CF EEC! B7D0 EEC! 01 TCTL1 C! 08 TMSK1 C! +INT ." INTERUPT ON " CR ; : TEST ON ." PRESS ANY KEY TO END " CR BEGIN ?TERMINAL UNTIL ." End " CR -INT 0 TCTL1 C! ABORT ;