In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Matthias09 wrote:

Guys, thanks a lot!

I appreciate your support!

PJMonty: looks up-in-the-sky and I tried and got it working! However: I monitored the variable CurrentPosition and it only has values between 0 and 1. What's wrong? My clue: I am not sure, if I can assign negative values to variables in SX/B. The compiler says ok, but I think I read somewhere that is not possible. Also your notation didn't work, so I adjusted, which was no problem but made me ask, if this code run on a SX28 before?

PJ Allen: it is an optical encoder, US Digital. Thanks for the hint with the SCHMITT command. SX 28 can use ST_B instead. However in the help file nothing is docummented about that. Any idea where I can find some information about that command?

[code]
 INTERRUPT	NOPRESERVE  6000

 '360*4 = 1440ppr. Max assumed speed: 2 rev/sec. max frequency = 2 rev/sec * 1440pulses/rev = 2880 pulses/sec. Nyquist: Scanning frequency
 '2x = 5760Hz == 6kHz

 ISR_Start:

'' WKPND_B = int_storage



'----- VERSION 5 -----

'Create a lookup table
EncoderTable(0)  =  0 
EncoderTable(1)  =  1
EncoderTable(2)  = -1
EncoderTable(3)  =  0

EncoderTable(4)  = -1
EncoderTable(5)  =  0 
EncoderTable(6)  =  0
EncoderTable(7)  =  1

EncoderTable(8)  =  1
EncoderTable(9)  =  0
EncoderTable(10) =  0
EncoderTable(11) = -1

EncoderTable(12) =  0
EncoderTable(13) = -1
EncoderTable(14) =  1
EncoderTable(15) =  0

' Get the current encoder values and mask un-used bits
CurrentEncoderInput = RC AND %00000011 

' Create entry into lookup table.  NOTE: Multiplying times 4 is the same as left
' shifting two places.  Depending on the compiler, the leftshift may be faster
PrevEncoderInput = PrevEncoderInput * 4
TableIndex = CurrentEncoderInput OR PrevEncoderInput 

' Update current position of encoder
CurrentPosition = CurrentPosition + EncoderTable(TableIndex)

' Store current encoder inputs for next time
PrevEncoderInput = CurrentEncoderInput 
[/code]

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