Reassigning I/O within the program ?

[Del Tapparo]

I would like to reassign I/O pins to specific variables based on the state of an input pin. Can I do this? e.g.

If Input = 1 then
Variable1 = PORTB.1
else
Variable1 = PORTB.2
endif

But the above doesn't work. Is there another way? I would like to do this at the beginning of the program, just once.

[Darrel Taylor]

You could use PIN numbers instead of PORT.bit.

InputSelect  VAR PORTB.0
myPIN        VAR BYTE

Test:
    IF InputSelect = 1 THEN
        myPIN = 1            ; PORTB.1 selected
    ELSE
        myPIN = 2            ; PORTB.2 selected
    ENDIF

    HIGH myPIN
    PAUSE 500
    LOW myPIN
    PAUSE 500
GOTO Test

Or, a similar version.
The Inputselect will always read 0 or 1. Add 1 to it to make 1 or 2, for PORTB.1 and PORTB.2.

InputSelect  VAR PORTB.0
myPIN        VAR BYTE

Test:
    myPIN = InputSelect + 1

    HIGH myPIN
    PAUSE 500
    LOW myPIN
    PAUSE 500
GOTO Test

The ports used depends on the chip you are using.
Check the .bas file for the PIC you are using in the PBP folder. (ex. 16F877a.bas)

PORTL and TRISL determine which PORT that pin numbers 0-7 go to.
PORTH and TRISH determine which PORT that pin numbers 8-15 go to.
<br><br>

[Del Tapparo]

Yes, there are many ways to achieve this within the loop of the main program. I was trying avoid having to make pin decisions every time I wanted to collect data. I just want to reassign the pins at the beginning of the program, and never worry about it again (i.e. less code).

Having thought about this for awhile now, I think the easiest way is to just make a subroutine for each data input (e.g. Get_Data) that makes the I/O pin decision each time I need the data. It still gobbles up a bunch of code, but is still relatively easy to follow the logic.

[Darrel Taylor]

Yes, there are many ways to achieve this within the loop of the main program. I was trying avoid having to make pin decisions every time I wanted to collect data. I just want to reassign the pins at the beginning of the program, and never worry about it again (i.e. less code).

I don't see a difference there.

If you set the PIN variable at the top of the program instead of in the main loop, it's the same thing.

Best regards,

[Del Tapparo]

I get it now ....

In my case, all of the reassigned inputs use the PULSIN command. I simply assign a variable to the pin portion of the PULSIN command, separate from the resulting input data variable.

Thanks Darrel! Much appreciated.

[tenaja]

I don't like needing to check the compiler files for information, because changing PICs can be a hassle, especially when you forget about it.

When I did it (years ago) I had to do something like this...
myPIN = 2 ...set this in your IF statements
low portb.0[myPIN] ...allows you to use any port you like, and changing PICs is easy.