Can PBP read optical encoder damn fast? :)

[HenrikOlsson]

If not pissing away 3/4 of the encoder resolution is something worth doing here's a replacement routine that does 4x decoding. It might not be the most optimized or elegant way but is works. Surprisingly (to me) it seems to work fine up to around 8kHz which means it does 32000 counts per second when being fed "perfect" quadrature signals my function gen.

' Added variables:
Encoder VAR BYTE
Old_Enc VAR BYTE
Test VAR BYTE
Dir VAR WORD          ' Must be same size as Position variable


'-------------------------------------------------------------
'--------------Poll encoder and keep count -------------------
'-------------Alternative routine with 4x decoding------------
'-------------------------------------------------------------

    Encoder.0 = Ch_A
    Encoder.1 = Ch_B

    Test = Encoder ^ Old_Enc

    Dir = 0

    If Test = 1 THEN
        If Old_Enc = 0 THEN Dir = 1
        IF Old_Enc = 1 THEN DIR = -1
        IF Old_Enc = 2 THEN Dir = -1
        If Old_Enc = 3 Then Dir = 1
    ENDIF

    IF Test = 2 THEN
        IF Old_Enc = 0 THEN DIR = -1
        IF Old_Enc = 1 THEN Dir = 1
        IF Old_Enc = 2 THEN Dir = 1
        IF Old_Enc = 3 THEN Dir = -1
    ENDIF

    Position = Position + Dir
    
    Old_Enc = Encoder

[Ioannis]

To me looks elegant enough! Wow, 32000 counts/s? I suppose on a fast 18F device, right?

Ioannis

[HenrikOlsson]

Same setup as before, 18F4520 @20MHz so not really that fast.
I don't know why it seems faster than the 1x version from earlier, perhaps I made a mistake when measuring either one of them.

[richard]

Henrik assuming i have implemented your ideascorrectly it works not at all well for a ky040 re in real life, i get about 400 counts per indent and rarely does it get direction correct.
my old code previously posted works near perfectly in the same rig either as isr or polled even a couple of .1uf across the pins does not help.

#CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
#ENDCONFIG


DEFINE OSC 32
    OSCCON=$70
    ANSELA=0
    OPTION_REG.6=0
    ENCODER    VAR BYTE   ;THE STATE OF THE ENCODER
    DIR   VAR BYTE    ;POSN
    Old_Enc  VAR BYTE    ;LAST MOVE 
    TEST   VAR BYTE 
    Position   VAR WORD 
    TRISA = %11111110
    lata.0=1 ;DEBUG
    Ch_A    VAR PORTA.4
    Ch_B    VAR PORTA.5
    
    
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0        
    DEFINE DEBUG_BAUD 38400
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug "Start",13 ,10
    Position =0 
    Old_Enc=0
    
mainloop:
'     Encoder.0= Ch_A    ;WON'T WORK AT ALL MOST TIMES
'     Encoder.1= Ch_B 
    Encoder = (PORTA&48)>>4
    Test = Encoder ^ Old_Enc
    Dir = 0
    If Test = 1 THEN
        If Old_Enc = 0 THEN Dir = 1
        IF Old_Enc = 1 THEN DIR = -1
        IF Old_Enc = 2 THEN Dir = -1
        If Old_Enc = 3 Then Dir = 1
    ENDIF
    IF Test = 2 THEN
        IF Old_Enc = 0 THEN DIR = -1
        IF Old_Enc = 1 THEN Dir = 1
        IF Old_Enc = 2 THEN Dir = 1
        IF Old_Enc = 3 THEN Dir = -1
    ENDIF
    Old_Enc = Encoder
    Position = Position + Dir
    IF DIR THEN 
        debug 13,10, "C",SDEC Position
    ENDIF
goto mainloop

my take [no pic18 worky or shitty old chips with no wreg access]

'****************************************************************'*  Name    : RE16.BAS                                          *
'*  Author  : RICHARD                                           *
'*  Notice  :                                                   *
'*          : All Rights Reserved                               *
'*  Date    : 5/06/2020                                         *
'*  Version : 1.0                                               *
'*  Notes   :    ONLY PIC16'S AND 12'S WITH WREG                *
'*          :   IN THIS INCARNTATION NO SHITTY OLD CHIPS        *
'****************************************************************


#CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
#ENDCONFIG


DEFINE OSC 32
    OSCCON=$70
    ANSELA=0
    OPTION_REG.6=0
    ev    VAR BYTE bank0   ;THE STATE OF THE ENCODER
    cnt   VAR WORD bank0   ;POSN
    TMP   VAR BYTE bank0   ;LAST MOVE IS 1, 0, -1
    TRISA = %11111110
    lata.0=1 ;DEBUG
    
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0        
    DEFINE DEBUG_BAUD 38400
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug "Start",13 ,10
    CNT=0 


mainloop:
ASM
    bcf STATUS,C      
    RLF _ev ,f        ;shift last reading into position
    bcf STATUS,C
    RLF _ev ,f
    MOVF PORTA,W     ;read enc pins 4,5
    ANDLW 48         ;mask off others
    SWAPF   WREG ,w  ;shift NEW reading into position
    IORWF _ev,F     ;combine this read with last read
    MOVF _ev,W     ;save ev
    ANDLW 15
    L?CALL enc_lut       ; decide to inc , dec or ignore 
    MOVWF _TMP         ;save decision
    BTFSC  _TMP,7
    GOTO myDEC16
    BTFSC  _TMP,0
    GOTO myINC16
enc_exit                    ;  exit
    GOTO OUT
myINC16
    INCF _cnt ,f
    BTFSC STATUS,Z
    INCF  _cnt +1 ,f 
    GOTO enc_exit
myDEC16
    MOVF  _cnt ,w
    BTFSC STATUS,Z
    DECF   _cnt +1, f   
    DECF   _cnt , f       
    GOTO enc_exit
OUT    
    ENDASM
    IF TMP THEN 
        debug 13,10,SDEC CNT
    ENDIF
goto mainloop


enc:
ASM
enc_lut                     ; the decision matrix
    addwf   PCL, F          
    retlw   0
    retlw   255
    retlw   1
    retlw   0
    retlw   1
    retlw   0
    retlw   0
    retlw   255
    retlw   255
    retlw   0
    retlw   0
    retlw   1
    retlw   0
    retlw   1
    retlw   255
    retlw   0  
ENDASM

[HenrikOlsson]

I have it running on the bench, works perfectly fine with an optical encoder (Scancon 2RMHF-500, 500 lines / 2000 edges per rev) - IRL :-)
Like I said previously I do not expect it to work reliably with a mechanical encoder unless it is properly debounced in hardware. Why your ASM version works with the same encoder I do not know :-(

You have a DEBUG statement within the loop - that will obviously mess up the timing but I know you know that.

[richard]

silly me i had the dir var as byte, it now works with this added change

' Encoder.0 = Ch_A
' Encoder.1 = Ch_B
encoder =(porta&48)>>4

reading the pins individually wont work for me @32mhz

[HenrikOlsson]

I made that exact mistake initially, hence the comment where the DIR variable is declared - yet I missed it when looking at you code...

I wonder why reading the pins individually doesn't work in your case. I only did it that way because CuriousOne wanted to be able to have the signals placed arbitrarily. I suspect though that reading them individually might be faster than masking and shifting.

I've been playing around with the math to go from encoder counts to actual frequency and I'm down to 110 cycles for calculating and stuffing the bits into the array. Had to resort to a tiny bit of ASM, getting the high word of a 16*16bit multiplication back from PBP without resorting to actually using LONGs.