Quad Encoder Problem


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  1. #1


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    Default Re: Quad Encoder Problem

    Quote Originally Posted by HenrikOlsson View Post
    Hi,
    Just realised I misunderstood you a bit. I thought you were trying to use the 12F1840 with this code, then I realised you're actually using the 16F1825 that's in the schematic...duh...

    Anyway, I've breadboarded a 12F1840 (don't have any 18F1825) and now have an encoder counting properly, sending the count over the USART. I simulated the EEPROM write by adding a PAUSEUS xxx in the handler and found that the limit for correct response - in my case - is around 500us. Anything above that it starts missing edges, coutning the wrong way etc.

    So, if the EEPROM write takes even remotely as long as 10ms then that is most likely the issue.

    /Henrik.
    Ok, it works now - mostly. What's weird is the 'MotorRPM' as displayed on the LCD jumps by 3-4 (i.e. current setting is '120' and then one click of the encoder makes it '124'). The only thing I did was comment out the WRITE line (and the PAUSE 100 too, of course). Sometimes, it misses incrementing the click completely (although only rarely).

    Does this have something to do with the comparison logic?

    Code:
    ' ***************************************************************
    ' [IOC - interrupt handler]
    ' ***************************************************************
    RotEncAdjust:
        New_Bits = PORTA & (%00000011)
        IF (New_Bits & %00000011) = (Old_Bits & %00000011) 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
    
    ;    WRITE EE_MotorRPM, MotorRPM
    ;    pause 100
    
    DoneRotEnc:
        Old_Bits = New_Bits
        
        IOCAF.0 = 0      ' Clear interrupt flags
        IOCAF.1 = 0
    
    @ INT_RETURN

  2. #2


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    Default Re: Quad Encoder Problem

    Another weird thing - If I comment out this line:

    Code:
    ' 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
    and these ones:

    Code:
    ' ***************************************************************
    ' [IOC - interrupt handler]
    ' ***************************************************************
    RotEncAdjust:
        New_Bits = PORTA & (%00000011)
        IF (New_Bits & %00000011) = (Old_Bits & %00000011) 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
    
    ;    WRITE EE_MotorRPM, MotorRPM
    ;    pause 100
    
    DoneRotEnc:
        Old_Bits = New_Bits
        
        IOCAF.0 = 0      ' Clear interrupt flags
        IOCAF.1 = 0
    
    @ INT_RETURN
    ... the interrupts don't seem to fire. And then the button push doesn't work, either (and that's not interrupt driven):

    Code:
    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

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