Custom array of ports using array?

[SteveB]

Paul:
Thanks for "chiming in" with a solution. I just want to make sure I understand what your code is trying to do so I can learn from it. I suspected there was a way to shoehorn this idea into PBP.

Relay[1] = 14  'RB6  is 14 bits offset from RA0
Relay[2] = 20  'RC4  is 20 bits offset from RA0
Relay[3] = 26  'RD2  is 26 bits offset from RA0

This array is establishing an offset from bit.0 on PORTA. I assume that most pics have PORTA-PORTX at consecutive regiester addresses (I only have a couple of datasheets to reference, but that's what I see)

for i = 1 to 3
     x = relay[i]
     porta.0[x]=1
     PAUSE 1000
     porta.0[x]=0
     PAUSE 300
next i

With the Relay[] array containing the correct offets, one can now use that with porta.0[x] to select the desire bit. Since porta.0 points to a bit, the offset [x] is in bits as well.
Did miss this "feature" in the PBP manual? Can I extend this idea further in that the inclusion of [X] to any reference that points to a register will actually cause an offset reference in accordance to the base reference. ( ie, if it was a word variable that [x] was added to, [x] would actually reference a register x*2 bytes offset?).


Steve

[paul borgmeier]

Steve,

Yes, you are 100% correct in the logic - that is exactly how it works. This “trick” is not in the manual but first appeared on the PicBasic List in 2002 (http://list.picbasic.com/forum/messages/4011/4739.html? ).

I remember being excited when this particular email came because it solved a problem I was having at the time. The links posted in my reply #6 above by Bruce and Melanie also clearly demonstrate this trick's use.

As I understand it, it works for all SF/GP Register locations, not just PORT bits, hence the indexed locations must be sequential like you mentioned. I always check the datasheet if I am going to use it on sequential Ports to make sure they are indeed sequential (and they always have been for the PICs I have used).


Paul

[Ingvar]

Since portpins rarely move(constants) you could use the LOOKUP statement to get the offset values. Should free up some RAM. The LOOKUP could ofcourse be placed in a subroutine if you need to access it from many different locations in your program. That way saving ROM.

x      var byte
i       var byte

main:
for i = 0 to 3
'               a  b  c  d
'               0  6  4  2
     LOOKUP i, [0,14,20,26], x
     porta.0[x]=1
     PAUSE 1000
     porta.0[x]=0
     PAUSE 300
next i

/Ingvar

[paul borgmeier]

Nice improvement! - The code for what blaine originally wanted to do is getting pretty clean considering it is an undocumented feature.

Best,

Paul

[Bruce]

Nice job Paul & Ingvar..;o}

Yet another version.

    DEFINE OSC 4

'   BASIC/ASM version = 172 words
    
    x   var word
    i   var byte
    RelayNum var PORTA
    
'    High byte = FSR / Low byte = port pin (or multiple pins)
    RLY1 CON %0000010100000001 ' PORTA|Bit0
    RLY2 CON %0000011001000000 ' PORTB|Bit6
    RLY3 CON %0000011100010000 ' PORTC|Bit4
    RLY4 CON %0000100000000100 ' PORTD|Bit2
    
    ADCON1 = 7
    PORTA = 0 : PORTB = 0 : PORTC = 0 : PORTD = 0
    TRISA = 0 : TRISB = 0 : TRISC = 0 : TRISD = 0
    
ASM
RelayOn macro
    movf  _x+1,w ; high byte = pointer to port file reg
    movwf FSR    ; load FSR
    movf  _x,w   ; low byte = port bit to change
    xorwf INDF,f ; toggle port pin
    endm
ENDASM

ASM
RelayOff macro
    movf  _x,w   ; reload port pin to toggle
    xorwf INDF,f ; do it
    endm
ENDASM
                         
main:
    for i = 0 to 3
        LOOKUP2 i, [RLY1,RLY2,RLY3,RLY4], x ' lookup file reg & XOR pattern
        @ RelayOn
        PAUSE 500
        @ RelayOff
        PAUSE 500
    next i
    
    END

[Darrel Taylor]

I agree, good stuff!

Here's another one.

INCLUDE "VirtualPort.bas"

Relays  VAR BYTE : Relays = 0

ASM
RelayPort  macro
    Vpin  0, PORTB, 6  ; RELAY1
    Vpin  1, PORTC, 4  ; RELAY2
    Vpin  2, PORTD, 2  ; RELAY3
  endm

  OutputPort  RelayPort    ; Set Port to OUTPUT
ENDASM

Then, here's a test loop to cycle thru the relays...

i  VAR BYTE

Main:
    for i = 0 to 2
        Relays = DCD i
        @  WritePort _Relays, RelayPort
        PAUSE 500
    next i
Goto Main

Code size = 104 words, 65 without the PAUSE.

or you can just...

Relays = %010
@  WritePort _Relays, RelayPort

to turn on RELAY2 by itself.
Code size = 21 words.

http://www.pbpgroup.com/Vport/VirtualPort.bas.txt

HTH,
    DT

[paul borgmeier]

Bruce, Darrel,

You guys are amazing yet again! I continue to learn and what good fun.

Paul

Edit - I am an ASL student (Assembly Second Language) student and removed some code from this post that was not correct.-pb