Display values from two PIC16F series controllers with one LCD display

[CBRUN17]

Art -

I completely agree with your assessment. Interfacing two channels of quadrature input is what I would prefer to do, however, I had huge issues just getting one to work reliably and fast! The current code interprets the quadrature signal (360 CPR) using ASM coded interrupt within PBP3 and it doesn't miss a beat! I was looking at another manufactures device and they actually do use two separate PICs with one LCD as I described in my original post. I agree this is a poor way to handle two inputs but after struggling for a couple of months with the existing code, I'm looking for whatever works at this point. I have to admit that the limitations I have are no more than my inexperience with PIC coding so far.

The code I use is similar to this:

'Read Quadrature Encoder and display value on LCD in .25 increments. for pic16f76

 '************************ DEFINES HERE *************************************
 DEFINE OSC 20 ' set to 20mhz
 DEFINE LCD_DREG PORTA ' Set Data Registers port
 DEFINE LCD_DBIT 0 ' Set starting data bit
 DEFINE LCD_RSREG PORTB ' Set LCD RS Port
 DEFINE LCD_RSBIT 1 ' Set LCD RS Bit
 DEFINE LCD_EREG PORTB ' Set LCD Enable Port
 DEFINE LCD_EBIT 2 ' Set LCD Enable Bit
 DEFINE LCD_BITS 4 ' Set LCD 4bit Mode
 DEFINE LCD_LINES 2 ' Set number of LCD Lines
 DEFINE LCD_COMMANDUS 2000 ' Set Command Delay time in uS
 DEFINE LCD_DATAUS 60 ' Set Data delay time in uS 

 clear 'clear out variables

 '*********************** CHIP REGISTER SETUP *******************************

 ADCON0 = 7 ' turn off analog porta, set to digital IO
 ADCON1 = 7 '
 CCP1CON = 0
 CCP2CON = 0
 
 TRISA = %00000000 ' output ports
 TRISB = %11000000 ' set input and output ports
 TRISC = %00100000 ' output ports
  
 portB.4 = 0
 portB.5 = 0
 
 '************************ PROGRAM VARIABLES HERE ***************************

 symbol   ledUp     = portC.2 ' status led
 symbol   ledDown = portC.3 ' status led2
 symbol   lcdbkl     = portC.4 ' lcd pannel backlight
 symbol   sw1        = portC.5 ' encoder switch
 symbol   ledTest   = portC.6
 

 enc_old                VAR BYTE
 enc_new              VAR BYTE
 enc_tmp              VAR byte
 enc_counter         VAR word bank0
 enc_counter_old   VAR word bank0
 enc_scaler            VAR word
 enc_dir                VAR enc_old.bit7
 Counter               VAR word bank0
 enc_SIGN            VAR counter.bit15
 Sign                    VAR BIT


 '*********************** ASSEMBLY INTERUPT VARIABLES ***********************
 wsave     VAR  byte $20 system
 wsave1   VAR  byte $a0 system ' Necessary for devices with RAM in bank1
 wsave2   VAR  byte $120 system ' Necessary for devices with RAM in bank2
 wsave3   VAR  byte $1a0 system ' Necessary for devices with RAM in bank3
 ssave     VAR  byte bank0 system
 psave     VAR  byte bank0 system 

 goto start 'skip over interupt handler
 '*********************** ASSEMBLY INTERUPT HANDLER *************************

 define INTHAND myint
 Asm

myint 
 ; Save W, STATUS and PCLATH registers
 movwf wsave
 swapf STATUS, W
 clrf STATUS
 movwf ssave
 movf PCLATH, W
 ;movwf psave 
 CLRF PCLATH


 ;====== BEGINNING OF THE ROTARY ENCODER CODE ========
 ;The Rotary Encoder is connected to PORTB 
 ;The A signal of the encoder connected to the PIN portB.7
 ;The B signal of the encoder connected to the PIN portB.6
 ;
 ;The 4 variables used are declared in the PicBasic code.
 ;
 ; enc_new VAR BYTE
 ; enc_old VAR BYTE
 ; enc_tmp VAR BYTE
 ; enc_counter VAR WORD
 ;
 ;================================================

 ;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 0xc0 ;Create bit mask (bits 7 & 6). b'11000000' ?
 andwf _enc_new,F ;Zero bits 5 thru 0.

    ;Check to see if encoder has moved
        movf    _enc_old,W         ;move enc_old to W
        movwf   _enc_tmp           ;put W to enc_tmp
        movf    _enc_new,W         ;move enc_new to W for XOR
        xorwf   _enc_tmp,F         ;XOR enc_tmp to detect encoder movement
        btfsc   STATUS,Z           ;if result is not zero, encoder moved.      
        goto    Continue           ;no movement exit isr

 ;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.
 bsf _ledDown ;turn on led

 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.
 bsf _ledUp ;turn on led

Continue 
 ;Assign the latest encoder inputs (in _enc_new) to _enc_old.
 movf _enc_new,W
 movwf _enc_old

 ; Restore saved registers
 movf  psave, W
 movwf PCLATH
 swapf ssave, W
 movwf STATUS
 swapf wsave, F
 swapf wsave, W
 bcf INTCON, RBIF ; Clear the Interupt Flag
 RETFIE ; Return from interrupt
 endasm

 '************************************************* **************************
 '************************* PROGRAM STARTS HERE *****************************
 '************************************************* **************************

 START: ' Main Program starts here
 INTCON = %10001000 ' Enable PortB Change Interupts 
 LCDOUT $FE,1 'Init The LCD
 pause 500 'wait for LCD to start 

 lcdout $FE,$80,  "TEST ANGLE DISP " 'display splash screen
 LCDOUT $FE,$C0,  "Initializing... " 
 high lcdbkl ' turn on backlight


 '************************** SET DEFAULT SETTINGS HERE **********************
 pause 2000 ' just wait a bit to read splash screen
 lcdout $FE,1
 enc_counter = 0 ' set default encoder value
 enc_counter_old = 0 
 Counter = 0
 
 
 lcdout $FE,$80, "Measurement   "
 lcdout $FE,$C0,"TST ANGLE: "


 '************************** TESTING ROUTINES HERE **************************
 test:
   If portC.5 = 0 then clearall
   
if enc_counter <> enc_counter_old then 'see if value has changed
    enc_counter_old = enc_counter 'move new value to old
        Counter = enc_counter '(enc_counter */ 250)/2
        Sign = Counter.15   ' Save sign
        Counter = ((ABS Counter) * 25) ' Degrees is now 0 to 900
        

If Sign THEN Counter = -Counter ' Restore sign, value is now -900 to 900


If not sign AND (-Counter < 0 or Counter > 0) then
    lcdout $FE,$80, "Measurement   "
    lcdout $FE,$C0,"TST ANGLE:", "-",sdec Counter /100 , ".", sdec Counter // 100, " " 
else
    lcdout $FE,$80, "Measurement   "
    lcdout $FE,$C0,"TST ANGLE:", " ", sdec -Counter /100 , ".", sdec -Counter // 100, " "
endif 

 
 low ledUp 'turn off CCW led
 low ledDown 'turn off CW led
 endif
 
 goto test

 ClearAll:
 
    enc_counter = 0
    enc_counter_old = 0 
    Counter = 0
    clear
    lcdout $FE,$80, "Measurement   "
    lcdout $FE,$C0,"TST ANGLE:", " 0.00 "
        high ledtest
            pause 1000
        low ledtest
 goto test
 
@INT_RETURN