Problem in Tension/compression

[precision]

This is my code for length measurements for fatigue testing machine with PEAK-HOLD.
I use 1000 PPR encoder with CH A and CH B for up/down, code working well when machine working in compression.
but problem is when machine work in tension side, encoder count 65535 below 00

i want this sequence

<<---------- 00 --------->>
Tension Compression
6-5-4-3-2-1-0-1-2-3-4-5-6

chip 16f88

DEFINE OSC 20
INCLUDE "MODEDEFS.BAS"
INCLUDE "MYLCD.BAS"

ANSEL = 0 'SELECT ANALOG INPUTS 0 = NONE AND ALL DIGITAL
ADCON0 = 0 'AD MODULE OFF & CONSUMES NO CURRENT
CMCON = 7 'COMPARATORS OFF

TRISA = %00000
TRISB = %00000011  ' INT0 = ENCODER CH. A
                   ' PORTB.1 = ENCODER CH. B
W0 VAR WORD
B1 var word
W0 = 0 
B1 = 0

PAUSE 500                           
'-------------------------------------------------------------------------
INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ; Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

OPTION_REG.6 = 0   ; 1 = Interrupt on rising edge of INT pin
                   ; 0 = Interrupt on falling edge of INT pin
                                      
@   INT_ENABLE   INT_INT     ; enable external (INT) interrupts

'-------------------------------------------------------------------------


LOOP:
          if W0 > B1 then B1 = W0 ' (Peak-Hold), Hold the last value of W0 in B1


          LCDOUT $FE,1
          LCDOUT "Length = ", dec5 w0, " mm"
          lcdout $FE, $C0
          lcdout "Peak- Value ",dec5 B1, " mm"
          pause 500          
         GOTO LOOP
         
ToggleLED1:                                    
        if PORTB.1 = 0 then
          W0 = W0+1
           else 
         w0 = w0-1 
         IF (W0 < 0) THEN
         W0 = 65535 + 1         
        endif 
        ENDIF
            
        @ INT_RETURN

[skimask]

W0 VAR WORD

         W0 = 65535 + 1

You have a word variable (16 bits)...
What's happens when you do the above math?
%1111111111111111 + %0000000000000001 = %10000000000000000
17 bits doesn't fit in a 16 bit variable.

An idea...divide all your numbers in half and use 32767 ($7FFF) as your new 'ZERO' point, change the LCD out routine to show that.

[precision]

When counts cross 65535, number will be 00000 and counts again upto 65535

but when i code
if W0 < 0 then W0 = 65535 + 1

after this counter will 00000 and hang on 00001

.

[skimask]

When counts cross 65535, number will be 00000 and counts again upto 65535
but when i code
if W0 < 0 then W0 = 65535 + 1
after this counter will 00000 and hang on 00001
.

That's my point...
W0 cannot be less than 'ZERO' with PBP...
PBP does not natively handle negative numbers using normal math routines. Yes there are a few commands that can handle signed integers, but not in the way you're looking to handle them. There are no 'minus' signs
You must figure out your own method to handle those negative numbers.

[Darrel Taylor]

precision,

Give this a try.

DEFINE OSC 20
INCLUDE "MODEDEFS.BAS"
INCLUDE "MYLCD.BAS"

ANSEL = 0 'SELECT ANALOG INPUTS 0 = NONE AND ALL DIGITAL
ADCON0 = 0 'AD MODULE OFF & CONSUMES NO CURRENT
CMCON = 7 'COMPARATORS OFF

TRISA = %00000
TRISB = %00000011  ' INT0 = ENCODER CH. A
                   ' PORTB.1 = ENCODER CH. B
W0     VAR WORD
LastW0 VAR WORD
B1     var word
W0 = 0 
B1 = 0

PAUSE 500                           
'-------------------------------------------------------------------------
INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ; Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

OPTION_REG.6 = 0   ; 1 = Interrupt on rising edge of INT pin
                   ; 0 = Interrupt on falling edge of INT pin
                                      
@   INT_ENABLE   INT_INT     ; enable external (INT) interrupts

'-------------------------------------------------------------------------
LCDOUT $FE,1

LOOP:   
        IF W0 <> LastW0 then
            LastW0 = W0
                 ' (Peak-Hold), Hold the last value of W0 in B1
            if ABS(LastW0) > ABS(B1) then B1 = LastW0

            LCDOUT $FE,2
            LCDOUT "Length = ", Sdec LastW0, " mm    "
            lcdout $FE, $C0
            lcdout "Peak- Value ",Sdec B1, " mm    "
        ENDIF
GOTO LOOP
         
ToggleLED1:                                    
        if PORTB.1 = 0 then
            W0 = W0+1
        else 
            w0 = w0-1 
        ENDIF
@ INT_RETURN

The range will be +/-32767.

Added: Modified slightly to eliminate changes while displaying.

Modified again to simplify. ABS() works for both pos and neg numbers. Doh!
It also fixes a problem if it moves slightly negative before going positive.
I'll get it right one of these times
<br>

[Darrel Taylor]

Just posting this for an email notification that I changed the program above.

In case you're already trying it.
<br>