HEDS5540 optical encoder

**louislouis** · - 2nd October 2016, 20:48

Hello boys,
I'm new on the forum and beginner in programming. I try to create a simple digital readout for X-axis on to my small lathe.
For simplicity I want to use rotary encoder and rack and pinion drive to measure distance.
I read and try all suitable codes I have found on the forum but a little success. I try combine this pieces of codes, but no success.
Please can someone to help me how to implement this code to functional end. MCU is 16F628A thank You for help.
This is my code:

Code:

INCLUDE "DT_INTS-14.bas"        ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"        ; Include if using PBP interrupts
 

'                       PIC 16F628A
' PicBasic program to demonstrate operation of an LCD in 4-bit mode
'          and reading an optical encoder in quadrature
'
' LCD should be connected as follows:
'       LCD     PIC
'       DB4     PortA.0
'       DB5     PortA.1
'       DB6     PortA.2
'       DB7     PortA.3
'       RS      PortA.4 (add 4.7K pullup resistor to 5 volts)
'       E       PortB.0
'       RW      Ground
'       Vdd     5 volts
'       Vss     Ground
'       Vo      20K potentiometer (or ground)
'       DB0-3   No connect
;       encoder ch A PortB.6
;       encoder ch B PortB.7

#config
   __config _HS_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _LVP_OFF & _CPD_OFF 
  #endconfig
  
DEFINE OSC 20  
  
TRISA    = %00000000 ' Make all PortA pins output
TRISB    = %11100000

Define LCD_DREG PORTA
Define LCD_DBIT 0
Define LCD_RSREG PORTA
define LCD_RSBIT 4
define LCD_EREG PORTB
define LCD_EBIT 0
define LCD_BITS 4
define LCD_LINES 2
define LCD_COMMANDUS 2000
define LCD_DATAUS 50

Flag var bit
wsave VAR BYTE    $70     SYSTEM  ; alternate save location for W 
enc_new VAR BYTE
enc_old VAR BYTE
enc_counter VAR WORD

; Set variable value @ startup
Flag = 0          
enc_new = 0
enc_old= 0
enc_counter = 0
        

Lcdout $fe, 1                       ' Clear LCD screen
Lcdout "Encoder test"               ' Display message
Pause 500 
@ INT_ENABLE RBC_INT            ; enable external (INT) interrupts
goto main_loop


asm
INT_LIST  macro    ; IntSource,        Label,  Type, Resetflag?
        INT_Handler    RBC_INT, _enc,  ASM,  yes
    endm
    INT_CREATE                      ; Creates the interrupt processor
    ;================================================
endasm
enc:
asm    

    ;Read latest input from PORTB & put the value in _enc_new.

         movf    PORTB,W
         movwf  _enc_new

         ;Strip off all but the 2 MSBs in _enc_new.

         movlw    B'11000000'    ;Create bit mask (bits 7 & 6).
         andwf   _enc_new,F         ;Zero bits 5 thru 0.

         ;Determine the direction of the Rotary encoder.  

         rlf     _enc_old,F         ;left shift it into _enc_old to align bit 6 of 
                                ;_enc_old with bit 7 of _enc_new.

         movf    _enc_new,W         ;Move the contents of _enc_new to W in order to XOR.
         xorwf   _enc_old,F        ;XOR previous inputs (in _enc_old) with latest
                                ;inputs (in W) to determine CW or CCW.
 
          btfsc   _enc_old,7         ;Test bit 7 of result (in _enc_old).  Skip next line
                             ;if it is 0 (direction is CCW).
         goto    Up            ;Bit is 1 (direction is CW).  Go around Down
                             ;and increment counter.


Down
         ;Decrements _enc_counter because the rotary encoder moved CCW.
    ;Decrements _enc_counter (16 bit value), sets Z on exit.
              
        decf    _enc_counter,F      ; Decrement low byte
        incfsz  _enc_counter,W      ; Check for underflow
        incf    _enc_counter+1,F    ; Update
        decf    _enc_counter+1,F    ; Fixup
        movf    _enc_counter,W
        iorwf   _enc_counter+1,W    ; Set Z bit
        
    ;Add here code for the CCW LED if needed.
         
         goto    Continue          ;Branch around UP.

Up
         ;Increments _enc_counter because the rotary encoder moved CW.
    ;Increments _enc_counter (16 bit value), sets Z on exit.

        incfsz  _enc_counter,W      ; Add one to low byte
        decf    _enc_counter+1,F    ; No carry (negates next step)
        incf    _enc_counter+1,F    ; Add one to high byte
        movwf   _enc_counter        ; Store updated low byte back.
        iorwf   _enc_counter+1,W    ; Set Z flag
        
    ;Add here code for the CW LED if needed.
    
Continue 
         
         ;Assign the latest encoder inputs (in _enc_new) to _enc_old.

         movf     _enc_new,W
         movwf   _enc_old

    ;============ END OF THE ROTARY ENCODER CODE =====
    endasm                     
@ INT_RETURN

Main_Loop:   
  
if Flag = 1 then
Lcdout $fe, 1                    
Lcdout Dec enc_counter     ; display counter value on LCD
Flag = 0
endif
goto Main_Loop
end

**richard** · - 2nd October 2016, 22:11

if Flag = 1 then

nowhere in your code is flag ever set to 1

**louislouis** · - 2nd October 2016, 22:25

you're right, in the ASM code I not have defined the flag=1. The question is how to do that.

**richard** · - 2nd October 2016, 22:56

easiest way

Code:

Flag var byte
wsave VAR BYTE    $70     SYSTEM  ; alternate save location for W 
enc_new VAR BYTE
enc_old VAR BYTE
enc_counter VAR WORD

Code:

asm    

    ;Read latest input from PORTB & put the value in _enc_new.
         MOVE?CB    1 ,_Flag
         movf    PORTB,W
         movwf  _enc_new

         ;Strip off all but the 2 MSBs in _enc_new.

         movlw    B'11000000'    ;Create bit mask (bits 7 & 6).
         andwf   _enc_new,F         ;Zero bits 5 thru 0.

         ;Determine the direction of the

**mark_s** · - 2nd October 2016, 23:21

Richard's way is the best. Just for referece it could also be done without asm since its not time sensitive.

Code:

old_enc_counter var word
Main_Loop:   
  
if enc_counter<> old_enc_counter then 'If change update LCD
Lcdout $fe, 1                    
Lcdout Dec enc_counter     ; display counter value on LCD
old_enc_counter = enc_counter
endif
goto Main_Loop
end

**louislouis** · - 2nd October 2016, 23:26

hmm, I try it and no change, still only the "encoder test" message on the LCD.
This line is ok MOVE?CB 1 ,_Flag what means the question mark.

**richard** · - 2nd October 2016, 23:38

This line is ok MOVE?CB 1 ,_Flag what means the question mark.

NOTHING , MOVE?CB IS THE NAME OF A PBP MACRO that moves a constant to a byte var
advantage is that the macro does all the banksel for you

more proper would be FOR YOUR isr vars

Code:

Flag var bit  bank0
enc_new VAR BYTE  bank0
enc_old VAR BYTE  bank0
enc_counter VAR WORD  bank0

**richard** · - 2nd October 2016, 23:50

plus I would rearrange the code like this , the way you have it the interrupt is enabled before its created
which may not be a good thing

Code:

 INCLUDE "DT_INTS-14.bas"        ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"        ; Include if using PBP interrupts
 
'                       PIC 16F628A
' PicBasic program to demonstrate operation of an LCD in 4-bit mode
'          and reading an optical encoder in quadrature
'
' LCD should be connected as follows:
'       LCD     PIC
'       DB4     PortA.0
'       DB5     PortA.1
'       DB6     PortA.2
'       DB7     PortA.3
'       RS      PortA.4 (add 4.7K pullup resistor to 5 volts)
'       E       PortB.0
'       RW      Ground
'       Vdd     5 volts
'       Vss     Ground
'       Vo      20K potentiometer (or ground)
'       DB0-3   No connect
;       encoder ch A PortB.6
;       encoder ch B PortB.7
 
Define LCD_DREG PORTA
Define LCD_DBIT 0
Define LCD_RSREG PORTA
define LCD_RSBIT 4
define LCD_EREG PORTB
define LCD_EBIT 0
define LCD_BITS 4
define LCD_LINES 2
define LCD_COMMANDUS 2000
define LCD_DATAUS 50

wsave VAR BYTE    $70     SYSTEM  ; alternate save location for W 
enc_new VAR BYTE   bank0
enc_old VAR BYTE   bank0
enc_counter VAR WORD   bank0
Flag var BYTE        bank0
        
Lcdout $fe, 1                       ' Clear LCD screen
Lcdout "Encoder test"               ' Display message
Pause 500 
 

asm
INT_LIST  macro    ; IntSource,        Label,  Type, Resetflag?
        INT_Handler    RBC_INT, _enc,  ASM,  yes
    endm
    INT_CREATE                      ; Creates the interrupt processor
    ;================================================
endasm
; Set variable value @ startup
Flag = 0          
enc_new = 0
enc_old= 0
enc_counter = 0
@ INT_ENABLE RBC_INT            ; enable external (INT) interrupts
Main_Loop:     
if Flag = 1 then
Lcdout $fe, 1                    
Lcdout Dec enc_counter     ; display counter value on LCD
Flag = 0
endif
goto Main_Loop
end
 
 
 enc:
asm    
    ;Read latest input from PORTB & put the value in _enc_new.
         MOVE?CB 1,_Flag
         movf    PORTB,W
         movwf  _enc_new
         ;Strip off all but the 2 MSBs in _enc_new.
         movlw    B'11000000'    ;Create bit mask (bits 7 & 6).
         andwf   _enc_new,F         ;Zero bits 5 thru 0.
         ;Determine the direction of the Rotary encoder.  
         rlf     _enc_old,F         ;left shift it into _enc_old to align bit 6 of 
                                ;_enc_old with bit 7 of _enc_new.
         movf    _enc_new,W         ;Move the contents of _enc_new to W in order to XOR.
         xorwf   _enc_old,F        ;XOR previous inputs (in _enc_old) with latest
                                ;inputs (in W) to determine CW or CCW.
 
         btfsc   _enc_old,7         ;Test bit 7 of result (in _enc_old).  Skip next line
                             ;if it is 0 (direction is CCW).
         goto    Up            ;Bit is 1 (direction is CW).  Go around Down
                             ;and increment counter.

Down
         ;Decrements _enc_counter because the rotary encoder moved CCW.
    ;Decrements _enc_counter (16 bit value), sets Z on exit.
              
        decf    _enc_counter,F      ; Decrement low byte
        incfsz  _enc_counter,W      ; Check for underflow
        incf    _enc_counter+1,F    ; Update
        decf    _enc_counter+1,F    ; Fixup
        movf    _enc_counter,W
        iorwf   _enc_counter+1,W    ; Set Z bit
        
    ;Add here code for the CCW LED if needed.
         
         goto    Continue          ;Branch around UP.
Up
         ;Increments _enc_counter because the rotary encoder moved CW.
    ;Increments _enc_counter (16 bit value), sets Z on exit.
        incfsz  _enc_counter,W      ; Add one to low byte
        decf    _enc_counter+1,F    ; No carry (negates next step)
        incf    _enc_counter+1,F    ; Add one to high byte
        movwf   _enc_counter        ; Store updated low byte back.
        iorwf   _enc_counter+1,W    ; Set Z flag
        
    ;Add here code for the CW LED if needed.
    
Continue 
         
         ;Assign the latest encoder inputs (in _enc_new) to _enc_old.
         movf     _enc_new,W
         movwf   _enc_old
         INT_RETURN
    ;============ END OF THE ROTARY ENCODER CODE =====
    endasm

**richard** · - 3rd October 2016, 07:57

tried your code on a 500 ppr opto encoder, it seems to be good

modified to run on 16f1825, full quad decode [2000 edges / rev]

Code:

  #CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF            
#ENDCONFIG
 
OSCCON=$70 
DEFINE OSC 32

INCLUDE "DT_INTS-14.bas"        ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"        ; Include if using PBP interrupts
 
'                       PIC 16F1825

;       encoder ch A Porta.4
;       encoder ch B Porta.5

enc_new VAR BYTE   bank0
enc_old VAR BYTE   bank0
enc_counter VAR WORD   bank0
Flag var BYTE        bank0
 
TRISA     = %111111    ' Make all pins Input 
trisc     = %11111111   ;Make all pins Input   
ANSELA=0     
ANSELC=0
;SETUP IOC REGS
IOCAP  =    %110000     ;POS EDGE
IOCAN  =    %110000      ;NEG EDGE
IOCAF  =     0             ;CLR INT FLAG
intcon.3 = 1     ;iocie
asm
INT_LIST  macro    ; IntSource,        Label,  Type, Resetflag?
        INT_Handler    IOC_INT, _enc,  ASM,  NO
    endm
    INT_CREATE                      ; Creates the interrupt processor
    
endasm
  ;debug   --------------------------
 TRISA.0     = 0
 lata.0=1
 pause 2000     ;debug
 serout2 PORTa.0,84, ["ready v3",13,10 ]    ;debug
  ;debug ------------------------------------
 
; Set variable value @ startup
Flag = 0          
enc_new = 0
enc_old= 0
enc_counter = 0
@ INT_ENABLE IOC_INT
Main_Loop:     
if Flag = 1 then
 serout2 PORTa.0,84, [#enc_counter,13,10 ]  
Flag = 0
endif
goto Main_Loop
end
 
 
  enc:
asm 
    ;Read latest input from PORTA & put the value in _enc_new.
         MOVE?CB 1,_Flag 
         CHK?RP   PORTA
         movf    PORTA,W
         RST?RP
         movwf  _enc_new
         ;Strip off all but the 2 MSBs in _enc_new.
         movlw    B'00110000'    ;Create bit mask (bits 7 & 6).
         andwf   _enc_new,F         ;Zero bits 5 thru 0.
         ;Determine the direction of the Rotary encoder.  
         
         rlf     _enc_old,F         ;left shift it into _enc_old to align bit 6 of 
                                ;_enc_old with bit 7 of _enc_new.
         movf    _enc_new,W         ;Move the contents of _enc_new to W in order to XOR.
         xorwf   _enc_old,F        ;XOR previous inputs (in _enc_old) with latest
                                ;inputs (in W) to determine CW or CCW.
 
         btfsc   _enc_old,5         ;Test bit 5 of result (in _enc_old).  Skip next line
                             ;if it is 0 (direction is CCW).
         goto    Up            ;Bit is 1 (direction is CW).  Go around Down
                             ;and increment counter.

Down
         ;Decrements _enc_counter because the rotary encoder moved CCW.
    ;Decrements _enc_counter (16 bit value), sets Z on exit.
              
        decf    _enc_counter,F      ; Decrement low byte
        incfsz  _enc_counter,W      ; Check for underflow
        incf    _enc_counter+1,F    ; Update
        decf    _enc_counter+1,F    ; Fixup
        movf    _enc_counter,W
        iorwf   _enc_counter+1,W    ; Set Z bit
        
    ;Add here code for the CCW LED if needed.
         
         goto    Continue          ;Branch around UP.
Up
         ;Increments _enc_counter because the rotary encoder moved CW.
    ;Increments _enc_counter (16 bit value), sets Z on exit.
        incfsz  _enc_counter,W      ; Add one to low byte
        decf    _enc_counter+1,F    ; No carry (negates next step)
        incf    _enc_counter+1,F    ; Add one to high byte
        movwf   _enc_counter        ; Store updated low byte back.
        iorwf   _enc_counter+1,W    ; Set Z flag
        
    ;Add here code for the CW LED if needed.
    
Continue 
         
         ;Assign the latest encoder inputs (in _enc_new) to _enc_old.
         movf     _enc_new,W
         movwf   _enc_old
         CHK?RP   IOCAF
         CLRF IOCAF
         INT_RETURN
    ;============ END OF THE ROTARY ENCODER CODE =====
    endasm

**louislouis** · - 3rd October 2016, 19:50

Thank You Richard for helping me. The your corrected code works, the routine counts up and down when I turn the encoder shaft cw or ccw, but if i mark the shaft starting position and turn on the MCU the reading is zero thats OK and when i slowly turn for example half turn and go back to marked position the encoder reading is not zero but less or more than zero. I think the routine not count correctly the encoder pulses, maybe the encoder send incorrect signals, I dont know.

**richard** · - 4th October 2016, 00:52

Thank You Richard for helping me. The your corrected code works, the routine counts up and down when I turn the encoder shaft cw or ccw, but if i mark the shaft starting position and turn on the MCU the reading is zero thats OK and when i slowly turn for example half turn and go back to marked position the encoder reading is not zero but less or more than zero. I think the routine not count correctly the encoder pulses, maybe the encoder send incorrect signals, I dont know

.

I tried my setup again more carefully and verified it works ok, several back and forth motions always returns to the zero mark as zero in either direction, so the question is does rbc_int on your chip react to every edge generated by the encoder the same as ioc_int on a 16f1825 / perhaps not

**louislouis** · - 4th October 2016, 16:39

Yes, that's the problem. The RBC_INT react with pin RB.0 on port B, because this pin operate the LCD ENABLE pin. If I try to use only portA to operate the LCD (with internal 4MHz oscillator) and on the PORTB pin RB.6 and RB.7 hang only the encoder A and B channel, rest pins configured to output the reading is perfect. Always after turning up and down randomly, slower, quicker etc. when I return to marked starting position the reading is zero. Now, how to solve this problem, how to "tell" to MCU the only pinRB.6 and RB.7 trigger the interrupt, not the entire portB

**richard** · - 4th October 2016, 23:17

"

Code:

If I try to use only portA to operate the LCD (with internal 4MHz oscillator) and on the PORTB pin RB.6 and RB.7 hang only the encoder A and B channel, rest pins configured to output the reading is perfect.

yes , makes sense . unfortunately setting or clearing a bit on a pic port entails a read of that port first , any read of portb clears the mismatch condition state for the rbc interrupt.
so even though only the bits 4 to 7 that are set as inputs can cause an interrupt on change a write to your "e" pin can cause changes to be missed .
if it won't keep up with the encoder using the int osc then use an i2c lcd display or a different pic

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