Quad Encoder Problem

[HenrikOlsson]

Hi,
Change the code so that you interrupt on one edge of one channel - only. (The rising edge of channel A for example).
In the ISR, poll "the other" channel, if it's low you're moving in one direction, if it's high you're moving in the other.
Verify that it works at "any" speed you may turn the encoder.

/Henrik.

[RossWaddell]

I tried this but nothing happens - the display changes erratically with encoder movement and only really goes up or down by 1:

#DEFINE USE_CUI_ROTARY_ENCODER  ; comment out if using Grayhill rotary encoder
                                ; which triggers an interrupt only once per detent

' 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

#IFDEF USE_CUI_ROTARY_ENCODER
    IOCAP.1  = 1                ' Enable positive (rising edge) change, PORTA.1
'   The CUI encoder goes thru a full quad cycle with 1 detent turn,
'     so only need to capture 1 edge (A channel, rising)

'   CH A
'   ====
'       ------        ------
'      |      |      |      |
'      |      |      |      |
'   ---        ------        ------

'   CH B
'   ====
'          ------        ------
'         |      |      |      |
'         |      |      |      |
'   ------        ------        ---

'   Detent markers
'   ==============
'   |               |              |
'   |               |              |

'   If interrupt is triggered, it means A had a rising edge:
'           If B = 0 Then CW
'           If B = 1 Then CCW
#ELSE
    ' For Grayhill encoder, 1 detent triggers only 1 edge
    IOCAP.0  = 1                ' Enable positive (rising edge) change, PORTA.0
    IOCAP.1  = 1                ' Enable positive (rising edge) change, PORTA.1
    IOCAN.0  = 1                ' Enable negative (falling edge) change, POARTA.0
    IOCAN.1  = 1                ' Enable negative (falling edge) change, PORTA.1
    IOCAF.0  = 0                ' Clear interupt-on-change flag
    IOCAF.1  = 0                ' Clear interupt-on-change flag
#ENDIF

@ INT_ENABLE  IOC_INT       ; Interrupt-on-Change interrupt

Main:
    ' Check if motor RPM has changed
    IF MotorRPM <> Old_RPM Then
        Old_RPM = MotorRPM
        GOSUB ChngMotorHPWM
    EndIF   
  
    If ValueDirty = 1 THEN
        TimeToSave = TimeToSave - 1
        If TimeToSave = 0 THEN           ' Time to save ?
            WRITE EE_MotorRPM, MotorRPM
            
            ValueDirty = 0               ' Clear the flag

            #IFDEF USE_LCD_FOR_DEBUG
                HSEROUT [LCD_INST, LCD_CLR]
                pause 5
                HSEROUT ["Saved RPM=", DEC MotorRPM, "  ", 13, 10] ' Send text followed by carriage return and linefeed
            #ENDIF
        ENDIF
    ENDIF
 
    GOTO Main

' ***************************************************************
' [IOC - interrupt handler]
' ***************************************************************
RotEncAdjust:
    #IFDEF USE_CUI_ROTARY_ENCODER
        IF PORTA.0 = 0 THEN
            RotEncDir = 1                 ; CW rotation if B channel is 0
        ELSE
            RotEncDir = 0                 ; CCW rotation
        ENDIF
    #ELSE
        New_Bits = PORTA & (%00000011)
    
        IF New_Bits = Old_Bits Then DoneRotEnc
    
        RotEncDir = New_Bits.1 ^ Old_Bits.0
    #ENDIF

    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
    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

(I left out the rest of the code)

[HenrikOlsson]

In theory it should work... Perhaps the interrupt latency is just too large to be able to catch the correct state of the 'other' channel once you get to the ISR. One way to test that is to try it with the Grayhill encoder, then it should count every 4th click. If it does then it's a timing problem, if it doesn't it's something else.

Nice demonstration of conditional compilation!

/Henrik.

[Ioannis]

Maybe an DSO can help here. Do you have access to such an instrument?

By the way as Henrik noted, I liked the conditional compilation too. Great example!

Ioannis

[RossWaddell]

If you mean an oscilloscope, no I don't have one (I'd like one, mind, but they're pretty darned expensive).

And thanks for compliment, Henrik & Ioannis! Although I got the idea from a Darrel Taylor post, I believe - this forum is such an excellent source of ideas.

[HenrikOlsson]

From a price/performance standpoint the Rigol DS1052E is quite hard to beat at around $350 and a very popular entry level scope. A very handy tool to have when working with electronics.

[RossWaddell]

From a price/performance standpoint the Rigol DS1052E is quite hard to beat at around $350 and a very popular entry level scope. A very handy tool to have when working with electronics.

Closer to $470 here in Canada, I'm afraid.