;**************************************************************************** ; * Rotary Encoder Decoder * ; * Version 1.1++ * ; * May 24, 2004 * ; * * ;**************************************************************************** ; Description: ; This program allows a PIC to decode quadrature rotary encoder signals to ; proved direction, tachometer and magnitude outputs. Each time the encoder ; is moved, a tach output pulse is generated, and both a direction and three ; bit magnitude vale are produced. The magnitude indicates how fast the ; shaft is being turned, and is based on the time that passes between encoder ; movements. ; ;**************************************************************************** ; Author - Bruce Stough - AA0ED ; ; Modification History ; 11/05/00 - Modified to use jump tables to determine the endoder direction. ; 4/29/01 - Modified to work with the 16f628 chip. ; 7/02/02 - Update Config definitions for 16F628 (CBJ) ; 7/29/03 - Minor tweaks (CBJ) ; 9/21/03 - Fix PIC16F628 picture. Pin 4 (!MCLR) goes to +5v, not GND (CBJ) ; 5/24/04 - Add comments re 50 ms timer (CBJ) ; ;**************************************************************************** ; ; Target Controller - PIC16F628 ; __________ ; RA2 |1 18| RA1---------ENCODER A ; RA3 |2 17| RA0---------ENCODER B ; RA4 |3 16| OSC1--------(Unused) ; +5v ----------!MCLR |4 15| OSC2--------(Unused) ; Ground----------Vss |5 14| VDD---------+5 V ; RB0 |6 13| RB7---------Direction ; RB1 |7 12| RB6---------Encoder bit ; RB2 |8 11| RB5---------Encoder mid bit ; Encoder tach----RB3 |9 10| RB4---------Encoder low bit ; ---------- ; ;**************************************************************************** ; ;**************************************************************************** ; * Device type and options. * ;**************************************************************************** ; processor PIC16F628 radix dec ; ;**************************************************************************** ; * Configuration fuse information for 16F628: * ;**************************************************************************** _BODEN_ON EQU H'3FFF' _BODEN_OFF EQU H'3FBF' _CP_ALL EQU H'03FF' _CP_75 EQU H'17FF' _CP_50 EQU H'2BFF' _CP_OFF EQU H'3FFF' _PWRTE_OFF EQU H'3FFF' _PWRTE_ON EQU H'3FF7' _WDT_ON EQU H'3FFF' _WDT_OFF EQU H'3FFB' _LVP_ON EQU H'3FFF' _LVP_OFF EQU H'3F7F' _MCLRE_ON EQU H'3FFF' _MCLRE_OFF EQU H'3FDF' _ER_OSC_CLKOUT EQU H'3FFF' _ER_OSC_NOCLKOUT EQU H'3FFE' _INTRC_OSC_CLKOUT EQU H'3FFD' _INTRC_OSC_NOCLKOUT EQU H'3FFC' _EXTCLK_OSC EQU H'3FEF' _LP_OSC EQU H'3FEC' _XT_OSC EQU H'3FED' _HS_OSC EQU H'3FEE' ; __config _CP_OFF & _LVP_OFF & _BODEN_OFF & _MCLRE_ON & _PWRTE_ON & _WDT_ON & _INTRC_OSC_NOCLKOUT ; __config H'3F34' ; ;**************************************************************************** ; * Port and EEPROM Constants * ;**************************************************************************** ; PortA equ 0x05 PortB equ 0x06 TRISA equ 0x05 TRISB equ 0x06 WREN equ 0x02 WR equ 0x01 RD equ 0x00 CMCON equ 0x1F PIR1 equ 0x0C PIE1 equ 0x8C TMR1L equ 0x0E TMR1H equ 0x0F T1CON equ 0x10 ; ; ;**************************************************************************** ; * RAM page independent file registers: * ;**************************************************************************** ; INDF EQU 0x00 PCL EQU 0x02 STATUS EQU 0x03 FSR EQU 0x04 PCLATH EQU 0x0A INTCON EQU 0x0B ; ;***************************************************************************** ; * Bit numbers for the STATUS file register: * ;***************************************************************************** ; B_RP0 EQU 5 B_NTO EQU 4 B_NPD EQU 3 B_Z EQU 2 B_DC EQU 1 B_C EQU 0 ; ;**************************************************************************** ; * Assign names to IO pins. * ;**************************************************************************** ; ; B register bits: ; tach_bit equ 3 dir_bit equ 7 speed_low equ 5 speed_high equ 6 ; ;*************************************************************************** ; * General program equates * ;*************************************************************************** clockwise equ 1 counter_cw equ 0 ; ; The following values determine the ren_timer_1 threshole values and the ; amount to increment the timer each time around. ; fast_1 equ 0x10 fast_2 equ 0x40 fast_3 equ 0x70 fast_4 equ 0xFF timer_inc equ 0x40 ; ;**************************************************************************** ; * Allocate variables in general purpose register space * ;**************************************************************************** ; CBLOCK 0x20 ; Start Data Block ; timer1 ; Used in delay routines timer2 ; " encoder_curr ; New value of encoder pins A and B encoder_old ; Old value of encoder pins A and B ren_read ; Encoder pins A and B direction ; Indicates last direction of encoder out_bits ; The direction and speed bits to PortB tick_count ; The count for this period init_flag ; Indicates when we are starting over temp_w ; Interrupt save of W temp_s ; Interrupt save of STATUS ; ENDC ; End of Data Block ;**************************************************************************** ; * The 16F84 resets to 0x00. * ; * The Interrupt vector is at 0x04. (Unused) * ;**************************************************************************** ; ORG 0x0000 goto start org 0x0004 goto int_server ;***************************************************************************** ; * * ; * Purpose: This is the start of the program. It polls the rotary encoder * ; * inputs. When it detects a change, it determines the direction * ; * the knob was turned and the speed at which it is turned and * ; * provides this as output. * ; * * ; * Input: The A and B outputs of the rotary encoder. * ; * * ; * Output: The direction, tach, and speed outputs. * ; * * ;***************************************************************************** ; start clrf INTCON ; No interrupts for now movlw 0x07 ; Code to turn off the analog comparitors movwf CMCON ; Turn off comparitors ; ; New stuff for timer 1 and interrupt. ; movlw 0xC0 ; Get GIE and PEIE bits movwf INTCON ; Enable general interrupts bsf STATUS,B_RP0 ; Switch to bank 1 to enable timer 1 movlw 0x01 ; Get bit to enable timer 1 interrupt movwf PIE1 ; Set TMR1IE bcf STATUS,B_RP0 ; Switch to bank 0 ; ; Initialize the timer to go for 50ms. ; Theory of operation: How to initialize the timer to interrupt after 50ms. (CBJ) ; ; TMR1IE bit is set, so an interrupt is generated when the counter rolls over. ; We will set a value into so the counter will always start at ; this value. Start at = 0x3CAF because 0xFFFF - 0x3CAF = 0xC3F0 - 50000. ; Thus, it will generate the interrupt after 50000 ticks of the timer. ; ; Timer1 gets incremented on every instruction cycle (Internal clock / 4). ; Prescale is 1:1, since is zero. ; The internal clock frequency is 4 MHz, so instruction cycle is 1 MHz. ; This means 1x10^-6 seconds per timer tick ; ; 5 x 10^4 ticks /interrupt x 1 x 10^-6 seconds / tick ; so we have 5 x 10^-2 seconds (which is 50 ms) per interrupt. ; ; clrf T1CON ; Turn TIMER1 off movlw 0xAF ; Get low byte movwf TMR1L ; Set low timer byte movlw 0x3C ; Get high byte movwf TMR1H ; Set high timer byte movlw 0x01 ; Bit to turn on TIMER1 movwf T1CON ; Turn the timer on ; clrf tick_count ; Initialize tick count to zero clrf init_flag ; Indicate we are starting over bsf STATUS,B_RP0 ; Switch to bank 1 bsf 0x01,7 ; Disable weak pullups movlw 0xFF ; Tristate port A movwf TRISA ; clrf TRISB ; Set port B to all outputs bcf STATUS,B_RP0 ; Switch back to bank 0 ; ; Get the power on encoder value. ; movf PortA,w ; Read port A movwf ren_read ; Save it in ren_read movlw 0x03 ; Get encoder mask andwf ren_read,w ; Get encoder bits movwf encoder_old ; Save in encoder_old clrf PortB ; Clear port B outputs goto main ; Jump around tables to main routine ; ;**************************************************************************** ; ; The CW and CCW jump tables return the encoder values expected if the encoder ; is moved clockwise or counter clockwise from the value passed in W. The ; returned value (based on the old encoder value) is compared with the new ; encoder value to determine the direction the knob was turned. ;***************************************************************************** CW addwf PCL,f ; Add offset to the program counter retlw 0x02 ; Value following 0x00 going clockwise retlw 0x00 ; Value following 0x01 going clockwise retlw 0x03 ; Value following 0x02 going clockwise retlw 0x01 ; Value following 0x03 going clockwise ; CCW addwf PCL,f ; Add offset to the program counter retlw 0x01 ; Value after 0x00 going counter clockwise retlw 0x03 ; Value after 0x01 going counter clockwise retlw 0x00 ; Value after 0x02 going counter clockwise retlw 0x02 ; Value after 0x03 going counter clockwise ; ; Fall into the Main Program Loop ; ;***************************************************************************** ; * * ; * Purpose: This is the Main Program Loop. * ; * * ; * Input: None. * ; * * ; * Output: None. * ; * * ;***************************************************************************** ; main call poll_encoder ; Check for knob movement movf init_flag,w ; Get the init flag sublw 0x01 ; Was it set? btfss STATUS,B_Z ; Was the Z flag set? goto not_init ; No: Not init condition movlw 0x01 ; Get a 1 to init tick_count movwf tick_count ; Start counting again movlw 0x00 ; Get a zero movwf init_flag ; Clear the init flag goto main ; Keep polling not_init movf tick_count,w ; Get the tick_count value sublw 0xFF ; Has it reached the limit? btfss STATUS,B_Z ; Skip increment if equal incf tick_count,f ; Increment the tick count ; ; Need to add stuff to check the direction. ; goto main ; Keep polling ; ;***************************************************************************** ; * * ; * Purpose: This routine polls the encoder until the value changes. * ; * When the first change is found, the direction the knob was * ; * turned is recorded in curr_dir. * ; * * ; * Input: The A and B encoder inputs. * ; * * ; * Output: direction -> an indication the direction the knob was turned. * ; * * ;***************************************************************************** ; poll_encoder clrwdt ; Reset the watchdog timer movf PortA,w ; Get the current encoder value movwf ren_read ; Save it movlw 0x03 ; Get encoder mask andwf ren_read,w ; Isolate encoder bits movwf encoder_curr ; Save new value xorwf encoder_old,w ; Has it changed? btfsc STATUS,B_Z ; Yes: Return directin goto poll_encoder ; No: Keep looking until it changes ; ; Determine which direction the encoder turned. ; movf encoder_old,w ; Get the old encoder value call CW ; Assume the knob is turning clockwise subwf encoder_curr,w ; See if the new value matches clockwise btfsc STATUS,B_Z ; Did we guess right? goto check_ccw ; No: Try counter clockwise movlw clockwise ; Get clockwise flag movwf direction ; Record the current direction goto exit_poll ; Prepare to return to the caller check_ccw movf encoder_old,w ; Get the old encoder value call CCW ; Get next value ccw from old encoder value subwf encoder_curr,w ; See if expected value matches curr encoder btfsc STATUS,B_Z ; Do they match? goto slip ; No: Handle slip movlw counter_cw ; Get counter clockwise flag movwf direction ; Record the current direction goto exit_poll ; Prepare to return to the caller slip movf encoder_curr,w ; Get the current encoder value movwf encoder_old ; Make it the new old value goto poll_encoder ; Keep looping exit_poll movf encoder_curr,w ; Get the current encoder bits movwf encoder_old ; Save them in encoder_old for the next time return ; Return to the caller ;***************************************************************************** ; * * ; * Purpose: This interrupt routine is call gets called on each timer * ; * interrupt. It sends any encoder steps to the main PIC. * ; * * ; * Input: * ; * * ; * Output: The three-bit encoder speed value, with the high bits cleared * ; * * ; **************************************************************************** int_server movwf temp_w ; Save the contents of W swapf STATUS,w ; Save STATUS contents movwf temp_s ; ; movlw 0x00 ; Prepare to clear timer 1 interrupt flag movwf PIR1 ; Clear timer 1 interrupt ; ; Strobe tach bit if the tick_count is non-zero. ; movf tick_count,w ; Get the tick_count sublw 0x00 ; Is it zero? btfsc STATUS,B_Z ; Is the zero bit clear? goto reinit ; No: tick_count was zero, skip strobe ; ; The encoder has been turned and the direction has been determined. ; Display the count code in bits B4-B6 based on the tick_count and the ; following table: ; ; tick_count B4-B6 Value ; 1 0 ; 2 1 ; 3-4 2 ; 5-8 3 ; 9-16 4 ; 17-32 5 ; 33-64 6 ; 64+ 7 ; movf tick_count,w ; Get the tick_count value sublw 0x01 ; Check for 1 btfsc STATUS,B_Z ; Was tick_count 1? goto set_zero ; Yes: Send 0 movf tick_count,w ; Get the tick_count value sublw 0x02 ; Check for 2 btfsc STATUS,B_Z ; Was tick_count 2? goto set_one ; Yes: Send 1 movf tick_count,w ; Get the tick_count value sublw 0x04 ; Was tick_count > 4? btfsc STATUS,B_C ; Was tick_count > 4? goto set_two ; No: Send 2 movf tick_count,w ; Get the tick_count value sublw 0x08 ; Was tick_count > 8? btfsc STATUS,B_C ; Was tick_count > 8? goto set_three ; No: Send 3 movf tick_count,w ; Get the tick_count value sublw 0x10 ; Was tick_count > 16? btfsc STATUS,B_C ; Was tick_count > 16? goto set_four ; No: Send 4 movf tick_count,w ; Get the tick_count value sublw 0x20 ; Was tick_count > 32? btfsc STATUS,B_C ; Was tick_count > 32? goto set_five ; No: Send 5 movf tick_count,w ; Get the tick_count value sublw 0x40 ; Was tick_count > 64? btfsc STATUS,B_C ; Was tick_count > 64? goto set_six ; No: Send 6 movlw 0x07 ; Yes: Send 7 goto send_result ; Issue value set_zero movlw 0x00 ; Send 0 goto send_result ; Issue value set_one movlw 0x01 ; Send 1 goto send_result ; Issue value set_two movlw 0x02 ; Send 2 goto send_result ; Issue value set_three movlw 0x03 ; Send 3 goto send_result ; Issue value set_four movlw 0x04 ; Send 4 goto send_result ; Issue value set_five movlw 0x05 ; Send 5 goto send_result ; Issue value set_six movlw 0x06 ; Send 6 goto send_result ; Issue value set_seven movlw 0x07 ; Send 7 send_result ; Issue value movwf out_bits ; Save value rlf out_bits,f ; Shift to B4-B6 bits rlf out_bits,f rlf out_bits,f rlf out_bits,f ; ; Set the direction. ; bsf out_bits,dir_bit ; Assume clockwise movf direction,w ; Get the direction value (0=CCW, 1=CW) btfss STATUS,B_Z ; Clockwise? bcf out_bits,dir_bit ; No: Indicate counter clockwise movf out_bits,w ; Get the bits to output movwf PortB ; Assert the direction and speed values ; bsf PortB,tach_bit ; Set the tach bit nop ; wait a bit bcf PortB,tach_bit ; Clear the tach bit ; ; Initialize the timer to go for 50ms. ; reinit movlw 0x00 ; Get zero to turn off TIMER1 movwf T1CON ; Turn TIMER1 off movlw 0xAF ; Get low byte movwf TMR1L ; Set low timer byte movlw 0x3C ; Get high byte movwf TMR1H ; Set high timer byte movlw 0x01 ; Bit to turn on TIMER1 movwf T1CON ; Turn the timer on ; movlw 0x01 ; Get the INIT flag movwf init_flag ; Indicate that we are starting over clrf tick_count ; Clear the tick count swapf temp_s,w ; Reswap STATUS, result in W movwf STATUS ; Restore STATUS swapf temp_w,f ; Swap saved W, result in temp_w swapf temp_w,w ; reswap, result in W retfie ; Return to normal execution ; ;***************************************************************************** ; * * ; * Purpose: Wait for a specified number of milliseconds. * ; * * ; * Entry point wait_128ms: Wait for 128 msec * ; * Entry point wait_64ms : Wait for 64 msec * ; * Entry point wait_32ms : Wait for 32 msec * ; * Entry point wait_16ms : Wait for 16 msec * ; * Entry point wait_8ms : Wait for 8 msec * ; * * ; * Input: None * ; * * ; * Output: None * ; * * ;***************************************************************************** ; wait_128ms ; ****** Entry point ****** movlw 0xFF ; Set up outer loop movwf timer1 ; counter to 255 goto outer_loop ; Go to wait loops wait_64ms ; ****** Entry point ****** movlw 0x80 ; Set up outer loop movwf timer1 ; counter to 128 goto outer_loop ; Go to wait loops wait_32ms ; ****** Entry point ****** movlw 0x40 ; Set up outer loop movwf timer1 ; counter to 64 goto outer_loop ; Go to wait loops wait_16ms ; ****** Entry point ****** movlw 0x20 ; Set up outer loop movwf timer1 ; counter to 32 goto outer_loop ; Go to wait loops wait_8ms ; ****** Entry point ****** movlw 0x10 ; Set up outer loop movwf timer1 ; counter to 16 ; Fall through into wait loops ; ; Wait loops used by other wait routines ; - 1 microsecond per instruction (with a 4 MHz microprocessor crystal) ; - 510 instructions per inner loop ; - (Timer1 * 514) instructions (.514 msec) per outer loop ; - Round off to .5 ms per outer loop ; outer_loop movlw 0xFF ; Set up inner loop counter movwf timer2 ; to 255 inner_loop decfsz timer2,f ; Decrement inner loop counter goto inner_loop ; If inner loop counter not down to zero, ; then go back to inner loop again decfsz timer1,f ; Yes, Decrement outer loop counter goto outer_loop ; If outer loop counter not down to zero, ; then go back to outer loop again return ; Yes, return to caller ; ;***************************************************************************** ; END