Quad Encoder Problem

[RossWaddell]

This works. Probably a bit inefficient having the TMR1 interrupt firing @ 8Hz, but if only writes to EEPROM if the value has changed:

 
' ***************************************************************
' Pin Connections
' ***************************************************************

' RA0/pin 13                       -> B pin of rotary encoder
' RA1/pin 12                       -> A pin of rotary encoder
' RA2/CCP3/pin 11                  -> Stbd motor PWM output (motor 1)
' RA3/MCLR/pin 4                   -> Button switch pin of rotary encoder
' RC0/pin 10                       -> Stbd motor direction signal (motor 1)
' RC1/CCP4/pin 9                   -> Port motor PWM output (motor 2)
' RC2/pin 8                        -> Port motor direction signal (motor 2)
' RC4/Tx/pin 6                     -> Serial LCD output
' RC5/Rx/pin 5                     -> Serial input
      
DEFINE OSC 16               ; Set oscillator 16Mhz
DEFINE HSER_TXSTA   20h     ; Set transmit status and control register
DEFINE HSER_BAUD    2400    ; Set baud rate

#CONFIG
   __config _CONFIG1, _FOSC_INTOSC & _WDTE_ON & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF
   __config _CONFIG2, _PLLEN_OFF & _STVREN_ON & _BORV_LO & _LVP_OFF
#ENDCONFIG

' ***************************************************************
' Initialization
' ***************************************************************

OSCCON   = %01111000        ' 16MHz internal osc

pause 100                   ' As advised by Darrel Taylor for EEPROM issue

APFCON0.2 = 0               ; Tx on RC4 for LCD display
APFCON0.7 = 0               ; Rx on RC5

BAUDCON.4 = 1               ; Transmit inverted data to the Tx pin

ANSELA    = 0               ; Digital only for all PortA pins
ANSELC    = 0               ; Diginal only for all PortC pins

TRISA     = %00001011       ' Make PORTA pins 0-1 input for rotary encoder,
                            ' pin 3 for rotary button
TRISC     = 0               ' Make all PORTC pins output

' The INTEDG bit of the OPTION_REG register determines on which edge the 
' interrupt will occur. When the INTEDG bit is set, the rising edge will 
' cause the interrupt. When the INTEDG bit is clear, the falling edge will 
' cause the interrupt. 
OPTION_REG.6 = 1             ' 1=Rising edge (default) or button "PRESS";
                             ' 0=Falling edge or button "RELEASE"

Old_Bits       VAR BYTE
New_Bits       VAR BYTE
RotEncDir      VAR BIT       ' 1=CW, 0=CCW
                             ' Rot Enc pin A connected to PortA.1;
                             ' Rot Enc pin B connected to PortA.0
Old_RPM        VAR BYTE
i              VAR BYTE

ButtonPress    VAR PORTA.3   ' Alias PORTA.3 as "ButtonPress"

TimeCnt     VAR Word      

ISRCounter  VAR BYTE
ValueDirty  VAR BIT

' ***************************************************************
' Includes
' ***************************************************************

INCLUDE "DT_INTS-14.bas"    ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"    ' Include if using PBP interrupts
                            ' --> copy both files to PBP main folder 
                            ' (i.e. c:\pbp3)
                                                                  
' ***************************************************************
' ASM Interrupt Definitions
' ***************************************************************
                                                                  
ASM
INT_LIST  macro    ; IntSource,         Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,    ReloadTMR1,   ASM,  no       ; MUST be first
        INT_Handler   TMR1_INT,    _T1handler,   PBP,  yes
        INT_Handler    IOC_INT, _RotEncAdjust,   PBP,  yes
    endm
    INT_CREATE     ; Creates the interrupt processor
ENDASM

;--- Change these to match the desired interrupt frequency -------------------
;--- See http://DarrelTaylor.com/DT_INTS-14/TimerTemplate.html for more Info.
@Freq       = 8                   ; Frequency of Interrupts in Hz
@Prescaler  = 8                   ; Timers Prescaler setting
T1CON = $30                       ; $30 = Prescaler 1:8, TMR1 OFF
; $00=1:1, $10=1:2, $20=1:4, $30=1:8 --  Must match @Prescaler value

' ***************************************************************
' Set default values
' ***************************************************************

Old_RPM = MotorRPM
Old_Bits = PORTA & (%00000011)
ISRCounter = 0


' Enable interrupts on RPM control now that motors are fully spun up
INTCON   = %10001000        ' Global int enabled, IOCI enabled, 
                            ' INTF flag bit 0 clr, IOCI flag bit 0 clr
IOCAP.0  = 1                ' Enable positive (rising edge) change
IOCAP.1  = 1                ' Enable positive (rising edge) change
IOCAN.0  = 1                ' Enable negative (falling edge) change
IOCAN.1  = 1                ' Enable negative (falling edge) change
IOCAF.0  = 0                ' Clear interupt-on-change flag
IOCAF.1  = 0                ' Clear interupt-on-change flag

@ INT_ENABLE   IOC_INT      ; Interrupt-on-Change interrupt
@ INT_ENABLE  TMR1_INT      ; enable Timer 1 interrupts
GOSUB StartTimer            ; Start Timer 1 ('MotorRPM' will be saved on every
                            ; interrupt if dirty

Main:
    ' Check if motor RPM has changed
    IF MotorRPM <> Old_RPM Then
        Old_RPM = MotorRPM
        GOSUB ChngMotorHPWM
    EndIF   
   
    TimeCnt = 0
	While ButtonPress = 0
	    TimeCnt = TimeCnt + 1
	    Pause 10
	    If TimeCnt > 500 Then BtnAction
	Wend
 
    BtnAction:
        If TimeCnt > 0 and TimeCnt < 200 Then
            PortEngDir = PortEngDir + 1
            If PortEngDir > 1 Then PortEngDir = 0
    
            WRITE EE_PortEngDir, PortEngDir
            #IFDEF USE_LCD_FOR_DEBUG
                HSEROUT [LCD_INST, LCD_CLR]
                pause 5
                HSEROUT ["PortEngDir=", DEC PortEngDir, "  ", 13, 10] ' Send text followed by carriage return and linefeed
            #ENDIF

            GOSUB ReversePortEng
        ElseIf TimeCnt >= 200 Then
            WRITE EE_MotorRPM, MotorRPM_Default  ; restore Default value
        
            MotorRPM = MotorRPM_Default
        EndIf
 
    GOTO Main


' ***************************************************************
' [IOC - interrupt handler]
' ***************************************************************
RotEncAdjust:
    New_Bits = PORTA & (%00000011)
;    IF (New_Bits & %00000011) = (Old_Bits & %00000011) Then DoneRotEnc
    IF New_Bits = Old_Bits Then DoneRotEnc

    ' Increment ISR counter (since quad encoder throws 4 interrupts
    ' for every single detent). Only want to update MotorRPM if this counter
    ' reaches 4 (i.e. a single detent)
    ISRCounter = ISRCounter + 1
    IF ISRCounter < 4 THEN DoneRotEnc

    RotEncDir = New_Bits.1 ^ Old_Bits.0
    IF RotEncDir = 1 Then
        ; CW rotation - increase speed but only to a max of 'MaxDuty'
        IF MotorRPM < MaxDuty then MotorRPM = MotorRPM + 1
    Else
        ' CCW rotation - decrease speed to a min of 0
        IF MotorRPM > 0 Then MotorRPM = MotorRPM - 1
    EndIF

;    GOSUB StartTimer            ; Start the TMR1 Timer to save MotorRPM
    ValueDirty = 1

    ISRCounter = 0
;    WRITE EE_MotorRPM, MotorRPM
;    pause 100

DoneRotEnc:
    Old_Bits = New_Bits

    IOCAF.0 = 0      ' Clear interrupt flags
    IOCAF.1 = 0

@ INT_RETURN

;____This routine is Called on each TMR1 Interrupt____________________________
T1handler:
    IF ValueDirty = 1 THEN
       WRITE EE_MotorRPM, MotorRPM  
;    GOSUB StopTimer             ; Stop the Timer
   
       ValueDirty = 0
    EndIf

@ INT_RETURN

;---[TMR1 reload - interrupt handler]-----------------------------------------
ASM                               ; Calculate Timer Reload Constant
ReloadInst  = 8                   ; # of Intructions used to reload timer
  if ((Prescaler == 1)||(Prescaler == 2)||(Prescaler == 4)||(Prescaler == 8))
MaxCount    = 65536 + (ReloadInst / Prescaler)
TimerReload = MaxCount - (OSC*1000000/4/Prescaler/Freq)
    if ((TimerReload < 0) || (TimerReload > (65535-ReloadInst)))
        error Invalid Timer Values - check "OSC", "Freq" and "Prescaler"
    endif
  else
      error Invalid Prescaler
  endif
ENDASM

@Timer1 = TMR1L                   ; map timer registers to a word variable
Timer1       VAR WORD EXT
TimerReload  CON EXT              ; Get the External Constant
TMR1ON       VAR T1CON.0          ; Alias the Timers ON/OFF bit

;---Reload Timer1------
ASM
ReloadTMR1
    MOVE?CT  0, T1CON, TMR1ON     ;  1     stop timer
    MOVLW    LOW(TimerReload)     ;  1     Add TimerReload to the 
    ADDWF    TMR1L,F              ;  1     value in Timer1
    BTFSC    STATUS,C             ;  1/2
    INCF     TMR1H,F              ;  1
    MOVLW    HIGH(TimerReload)    ;  1
    ADDWF    TMR1H,F              ;  1
    MOVE?CT  1, T1CON, TMR1ON     ;  1     start timer
  INT_RETURN
ENDASM

;---Start/Stop controls -----
StartTimer:
    Timer1  = TimerReload         ; Load Timer
    TMR1ON = 1                    ; start timer
RETURN

StopTimer:
    TMR1ON = 0                    ; stop timer
RETURN

(When I turn off the PIC and turn it on again, it sometimes seems to speed up the motor to (MotorRPM - 1), i.e. 1 less than what was displayed on the LCD before turning off power.

[HenrikOlsson]

I'll try this out. At first glance, though, the ISR is always setting TimeToSave to 5000 so I think it needs a check like:

Well, yes, that was the whole idea. As long as the user keeps turning the knob (generating interrupts) the counter will get reset to 5000 (or whatever). But as soon as the user has NOT changed the RPM for the duration of 5000 iterations thru the Main loop the value is saved. When the knob isn't being turned no interrupts are being generated so the Main routine eventually gets the counter down to 0 and saves the value.

/Henrik.

[RossWaddell]

Oop. Yeah, of course that makes sense. Thanks.

[RossWaddell]

I incorporated your idea, Henrik, and all is well. I could have sworn this was working earlier this year when I last touched it but perhaps if using the same chip and saving too often to EEPROM means it starts to take longer to do the WRITE and hence only then really missed out on the IOC's. I thought it also incremented MotorRPM by 1 but I can't prove that now. In the end, it works with using a ISR counter and only on the 4th one does it increment MotorRPM.

I upped the TimeToSave value to 50000 - seems like a good compromise.

[RossWaddell]

Should I be setting Old_Bits to New_Bits in the 'DoneRotEnc' label for the first 3 of 4 interrupts related to an IOC?

' ***************************************************************
' [IOC - interrupt handler]
' ***************************************************************
RotEncAdjust:
    New_Bits = PORTA & (%00000011)

    IF New_Bits = Old_Bits Then DoneRotEnc

    ' Increment ISR counter (since quad encoder throws 4 interrupts
    ' for every single detent), only want to update MotorRPM when counter
    ' reaches 4 (i.e. a single detent 'click')
    ISRCounter = ISRCounter + 1
    IF ISRCounter < 4 THEN DoneRotEnc

    RotEncDir = New_Bits.1 ^ Old_Bits.0
    IF RotEncDir = 1 Then
        ; CW rotation - increase speed but only to a max of 'MaxDuty'
        IF MotorRPM < MaxDuty then MotorRPM = MotorRPM + 1
    Else
        ' CCW rotation - decrease speed to a min of 0
        IF MotorRPM > 0 Then MotorRPM = MotorRPM - 1
    EndIF

    ValueDirty = 1                   ; Set dirty flag
    ISRCounter = 0                   ; Reset ISR entry counter
    TimeToSave = 50000               ; Set value to begin countdown to EEPROM save

DoneRotEnc:
    Old_Bits = New_Bits

    IOCAF.0 = 0                     ' Clear interrupt flags
    IOCAF.1 = 0

@ INT_RETURN

[HenrikOlsson]

Hi,
I'm afraid I don't quite understand. A quadrature signal consists of four states (00-10-11-01), from any one state there are TWO valid states which it can "transition" to, one in either direction. If you don't keep track of Old_Bits it doesn't know in which state it was and will get confused, count in the wrong direction etc - just as it did when you had the delay in there. Are you trying to keep the MotorRPM from incrementing by 4 for each click?

Why don't you simply have an EncoderCount variable which is the one you save to EEPROM, and then you do MotorRPM = EncoderCount / 4. Also, instead of triggering on both the rising and falling edges you could trig on only the rising (or falling) which would give you two counts per click instead of four.

/Henrik.

[RossWaddell]

But if the interrupts are meant to fire on either a rising or falling edge, then going from '00' to '10' has only one edge (A rises from 0 to 1; B stays the same). The 00 to 10 state change represents one detent, right?

I got this ISR code from another post (http://www.picbasic.co.uk/forum/show...5396#post25396) and it seemed to work back then (incrementing MotorRPM by 1)

[Ioannis]

Are you sure this code does work on both directions?

Should I be setting Old_Bits to New_Bits in the 'DoneRotEnc' label for the first 3 of 4 interrupts related to an IOC?

' ***************************************************************
' [IOC - interrupt handler]
' ***************************************************************
RotEncAdjust:
    New_Bits = PORTA & (%00000011)

    IF New_Bits = Old_Bits Then DoneRotEnc

    ' Increment ISR counter (since quad encoder throws 4 interrupts
    ' for every single detent), only want to update MotorRPM when counter
    ' reaches 4 (i.e. a single detent 'click')
    ISRCounter = ISRCounter + 1
    IF ISRCounter < 4 THEN DoneRotEnc

    RotEncDir = New_Bits.1 ^ Old_Bits.0
    IF RotEncDir = 1 Then
        ; CW rotation - increase speed but only to a max of 'MaxDuty'
        IF MotorRPM < MaxDuty then MotorRPM = MotorRPM + 1
    Else
        ' CCW rotation - decrease speed to a min of 0
        IF MotorRPM > 0 Then MotorRPM = MotorRPM - 1
    EndIF

    ValueDirty = 1                   ; Set dirty flag
    ISRCounter = 0                   ; Reset ISR entry counter
    TimeToSave = 50000               ; Set value to begin countdown to EEPROM save

DoneRotEnc:
    Old_Bits = New_Bits

    IOCAF.0 = 0                     ' Clear interrupt flags
    IOCAF.1 = 0

@ INT_RETURN

By the time that ISRCounter is 4, both outputs of the encoder will be at 0. So the RotEncDir will be 0 too and only the ELSE expression will be executed.

Maybe I am missing something here?

Ioannis

[RossWaddell]

I have to admit, Ioannis, the code was grabbed from an example here and implemented on my side using a Grayhill encoder which only triggered the interrupt once per detent. Works perfectly with that device, With the CUI ACZ11, I added the check on the ISRCounter but it **does** work - both CW & CCW rotations are captured correctly.