In SX Microcontrollers, SX/B Compiler and SX-Key Tool, robotnerd007 wrote:

I am storing the encoder value in a word variable; however, i need more space than a word variable can provide. I really need to count up to around 90,000 pulses. I was wondering how to do this is. I would not mind sacrificing some resolution to get a greater range of distance that i could count. I dont really know how to modify the code i have to only detect 2 of the edge changes instead of the 4 that it does now. Is there another easier way to do this that i dont know about or am overlooking? Here is a copy of the code that i am using now.

DEVICE          SX28, OSCHS3, TURBO, STACKX, OPTIONX
FREQ           50_000_000
ID              "ENCODER"
' -------------------------------------------------------------------------
' IO Pins
' -------------------------------------------------------------------------
EncPort         VAR     RA                      ' encoder port
TRIS_Enc        VAR     TRIS_A
' -------------------------------------------------------------------------
' Constants
' -------------------------------------------------------------------------
MaxVal          CON     100
EndVal           con  17000
SlowVal         con EndVal-2000

' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------
encCheck        VAR     byte
encOld          VAR     byte                    ' previous encoder bits
encNew          VAR    byte                   ' new encoder bits
encValue        VAR     word                    ' encoder value
tmpB3           VAR     Byte
' -------------------------------------------------------------------------
  INTERRUPT
' -------------------------------------------------------------------------
' Runs every 64 uS @ 4 MHz (no prescaler)
ISR_Start:
  encNew = EncPort & %00000011                  ' get econder bits
  tmpB3 = encOld XOR encNew                     ' test for change
  IF tmpB3 > 0 THEN                             ' change?
    encOld = encOld << 1                        ' adjust old bits
    encOld = encOld XOR encNew                  ' test direction
    IF encOld.1 = 1 THEN
      IF encValue < EndVal THEN                 ' if max, no change
        INC encValue                            ' increase value
      ENDIF
    ELSE
      IF encValue > 0 THEN                      ' if 0, no change
        DEC encValue                            ' decrease value
      ENDIF
    ENDIF
    encOld = encNew                             ' save last input
  ENDIF 
ISR_Exit:
  RETURNINT
' =========================================================================
  PROGRAM Start
' =========================================================================
' -------------------------------------------------------------------------
' Subroutine Declarations
' -------------------------------------------------------------------------

' -------------------------------------------------------------------------
' Program Code
' -------------------------------------------------------------------------
Start:
  encNew = EncPort & %00000011                  ' read encoder pos
  encOld = encNew                               ' copy
  encValue = 0                                  ' clear value
  OPTION = $88                                  ' interrupt, no prescaler
' =========================================================================

low rc.7

main:                              ' clear value
Do
If encValue = EndVal then goto stop 'tells BS2 when to slow down and when to stop a robot
IF encValue = SlowVal then goto slowdown
loop


slowdown:
high RC.7
goto main

stop:
low RC.7
end

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