pic508_motor.asm

步进电机原理与使用

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*用PIC12C508509 控制一个步进电机源程序 *
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;   用PIC12C508509 控制一个步进电机源程序
    ; STEP_3.ASM (12C508 / 12C509)
   ;
   ; Controls a stepping motor driver on GPIO bits 4, 2, 1 and 0. 
   ;
   ; The direction is controlled by a switch on GPIO bit 3. Bit 5 is not
   used.
   ;
   ; (Typical drivers might include a ULN2803 Octal Driver, 2N2222 or TIP122
   ; transistors or power FETs. See Parallel Port Manual - Vol 1).
   ; 
   ; Outputs patterns 0x01, 0x03, 0x02, 0x06, 0x04, 0x0c, 0x08, 0x09, 0x01,
   ; .. in sequence to advance stepping motor in one direction. This is 
   ; achieved by causing INDEX to advance from 0 to 7, to 0, etc and 
   ; mapping the INDEX into a pattern which is then output on bits 4, 2, 1 
   ; and 0 of GPIO.
   ;
   ; Note that GPIO bit 3 is not used. Thus, prior to outputting, bit 3
   ; of PATT is copied to the bit 4 position.
   ;
   ; Motor is advanced in the other direction by causing INDEX to move in 
   ; the opposite direction; 7 to 0 to 7, etc.
   ;
   ; Switch on GPIO, Bit 3 is read between each output to the stepping 
   ; motor to determine whether INDEX is to be incremented (0-7, 0) or 
   ; decremented.
   ;
   ; The delay in between steps determines the speed of the stepper. In 
   ; this program it is 25 msecs. 
   LIST P=PIC12C509
   __CONFIG 0EH ; MCLR - dis, CP - dis, WDT - dis, FOSC - int
   #include <c:\mplab\P12C509.INC>
   CONSTANT BASE_VAR=07H
   INDEX EQU BASE_VAR+0 
   PATT EQU BASE_VAR+1
   LOOP1 EQU BASE_VAR+2 ; for timing loop
   LOOP2 EQU BASE_VAR+3
   ORG 000H
   MOVLW 080H ; GPWU disabled, GPPU enabled, other bits not used
   OPTION
   MOVLW B'101000'
   TRIS GPIO ; Bit 3 input, Bits 4, 2, 1 and 0 ouputs

   CLRF INDEX ; start INDEX at zero
   READ_SW: 
   BTFSC GPIO, 3 ; read direction switch
   GOTO FORWARD
   GOTO REVERSE
   FORWARD:
   INCF INDEX, F ; increment the index
   MOVLW .8
   SUBWF INDEX, W ; and test if equal to 8
   BTFSC STATUS, Z
   CLRF INDEX ; if at 8, set to 0
   GOTO ONE_STEP
   REVERSE:
   DECF INDEX, F ; decrement the index
   MOVLW 0FFH
   SUBWF INDEX, W ; test if at 0xFF
   BTFSC STATUS, Z
   GOTO REVERSE_1 ; if at FF, then reset to 7
   GOTO ONE_STEP
   REVERSE_1:
   MOVLW .7
   MOVWF INDEX
   GOTO ONE_STEP
   ONE_STEP:
   MOVF INDEX, W ; copy count into w
   CALL GEN_PATT ; returns the correct pattern in w
   MOVWF PATT ; save it
   BTFSS PATT, 3 ; move bit 3 to bit 4
   BCF PATT, 4
   BTFSC PATT, 3
   BSF PATT, 4
   MOVF PATT, W
   MOVWF GPIO
   CALL DELAY ; 25 msecs 

   GOTO READ_SW
   ;;;;;;
   GEN_PATT ; maps INDEX into appropriate stepping motor pattern
   MOVF INDEX, W 
   ADDWF PCL, F ; add w to the program counter 
   RETLW 01H ; stepping motor patterns
   RETLW 03H
   RETLW 02H
   RETLW 06H
   RETLW 04H
   RETLW 0CH
   RETLW 08H 
   DELAY: ; provides nominal 25 msec delay
   MOVLW .25
   MOVWF LOOP1
   OUTTER:
   MOVLW .110
   MOVWF LOOP2
   INNER:
   CLRWDT
   NOP
   NOP
   NOP
   NOP
   NOP
   DECFSZ LOOP2, F
   GOTO INNER
   DECFSZ LOOP1, F
   GOTO OUTTER
   RETURN
   END