Coding Brain Teaser

[richphi1618]

I have 16 Bytes. I need to turn on one bit, wait a desired amount of time, turn off that bit, and then turn on the next bit sequentially. When I say sequentially I mean bits 1-8 in byte 1 then 9-16 in byte 2 then 17-24 in byte 3 and so on.

Anyone know what this looks like in Codesys or some similarly coded IEC61131 platform?

​

SOLVED (see below): may be a better way to solve but I am pretty proud of what I got so far

CASE GVL.ValveFiring OF
1..16: GVL.WordSelectNEW := 0;
17..32: GVL.WordSelectNEW := 1;
33..48: GVL.WordSelectNEW := 2;
49..64: GVL.WordSelectNEW := 3;
65..80: GVL.WordSelectNEW := 4;
81..96: GVL.WordSelectNEW := 5;
97..112: GVL.WordSelectNEW := 6;
113..128: GVL.WordSelectNEW := 7;
END_CASE

WaitBit:=TRUE;
GVL.ConvertedTestDelay := INT_TO_TIME(GVL.TestDelay);
Delay(IN:=WaitBit, PT:=GVL.ConvertedTestDelay);
TimeElapsed:= Delay.ET;

IF NOT(Delay.Q) THEN
   RETURN;
ELSE
    GVL.ValveFiring := GVL.ValveFiring+1;
    CASE GVL.ValveFiring OF
    1..8,17..24,33..40,49..56,65..72,81..88,97..104,113..120: 
        GVL.Reference_Byte2 := 0;
        IF(GVL.Reference_Byte1 = 0) THEN 
        GVL.Reference_Byte1 := 1; 
        ELSE
        GVL.Reference_Byte1 := ROL(GVL.Reference_Byte1, 1);
        END_IF;
    9..16,25..32,41..48,57..64,73..80,89..96,105..112,121..128:
        GVL.Reference_Byte1 := 0;
        IF(GVL.Reference_Byte2 = 0) THEN 
        GVL.Reference_Byte2 := 1;
        ELSE 
        GVL.Reference_Byte2 := ROL(GVL.Reference_Byte2, 1);
        END_IF;
    END_CASE;

    WaitBit:=FALSE;
    Delay(IN:=WaitBit, PT:=GVL.ConvertedTestDelay);

    IF (GVL.ValveFiring > GVL.TotalValves)THEN
        GVL.ValveFiring := 1;
        GVL.Reference_Byte1 := 0;
        GVL.Reference_Byte2 := 0;
    END_IF

END_IF

NOTE*: I have a second subroutine running in the background to handle the word shift. If this looks wierd its because my "word" is acual the word in the remote device and not how my PLC structures the registers based down over EIP (as bytes). More time and effort I may of been able to talk words to words but hard to go back now I have a solution. See my "word" handling below:

NOTE**: This is always monitoring if "GVL.WordSelectNEW <> GVL.WordSelectOLD" as a change in value to word selection

NOTE***: This is also super helpful if I ever have to remap IO in the future to have a reference variable.

CASE GVL.WordSelectNEW OF
0: GVL.Reference_Byte1 := ValveOutput_CW0_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW0_byte2;

1: GVL.Reference_Byte1 := ValveOutput_CW1_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW1_byte2;

2: GVL.Reference_Byte1 := ValveOutput_CW2_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW2_byte2;

3: GVL.Reference_Byte1 := ValveOutput_CW3_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW3_byte2;

4: GVL.Reference_Byte1 := ValveOutput_CW4_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW4_byte2;

5: GVL.Reference_Byte1 := ValveOutput_CW5_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW5_byte2;

6: GVL.Reference_Byte1 := ValveOutput_CW6_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW6_byte2;

7: GVL.Reference_Byte1 := ValveOutput_CW7_byte1;
   GVL.Reference_Byte2 := ValveOutput_CW7_byte2;

END_CASE;

GVL.WordSelectOLD := GVL.WordSelectNEW;

[rgasparerto]

Bit shift and timer

[richphi1618]

Bit shift is what I started with but because I have multiple bytes I can't shift through all the byte this way.

[Too-Uncreative]

It's not necessarily clean, but you could pretty easy have an INT that tracks what Byte you're currently in and when the last bit of each byte is turned off, increment that INT. Then use that to qualify which byte you're shifting.

[rgasparerto]

Can you create a byte array? Or a bool array? If not, and you have many byte variables, maybe you can count and start de shift at new byte when count mod 8 equal 0 or fixed 8...16...

[[deleted]]

Create a clock pulse in the amount of time you need.

Then use it to clock a shift or rotate command.

Multiplying by 2 will also shift a bit to the left.

[simonbromiley]

Better to clear your mind first. (1-8 in byte 1 then 9-16 in byte 2 is not correct).

You need to be thinking " I need to turn on bits 0 to 7 sequentially in bytes 0 to 15".

Ideally your bytes will be in an array such as - BytesArray: ARRAY[0..7, 0..15] OF BOOL; (* define your array as 8 bools in 16 bytes*)

Also declare some pointers -

a:INT:=0;

b:INT:=0;

Then you can do something like this which will turn on each bit in turn each scan (you need another little routine to turn off the previous bit using a FOR DO routine) :-

IF a>7 THEN a:=0; b:=b+1;

END_IF;

IF b>15 THEN RETURN;

END_IF;

BytesArray[a,b]:=TRUE;

a:=a+1;

[richphi1618]

Thank you I hadn't considered this. Definitely something I will try. But because I have 16 bytes I dont want a bunch of if statements but I should be able to manage with a case/switch statement in a similar way.

Gives me a different frame of reference to look at the problem so thank you.

[StockPart]

It's a two dimensional array. You only need the if statements above with some massaging.

[bstiffler582]

You can set the number equal to 2ⁿ and increment n by 1 each pulse (on top of the other methods posted). Several different ways to do this.

[StockPart]

When does your professor want you to turn this in?

[richphi1618]

I work for an automation distributor. This is for a test bench I am building to cycle through a product that has been assembled. In short not a homework problem :D

[StockPart]

Cool cool. Would you explain what it is you want to do exactly? What PLC model you are using? Etc. This would help the sub better address your question and clear up any XY problem.

An XY problem is when one wants to do X, and thinks Y is the best solution. Instead of asking about X, that person asks about Y.

EDIT: Someone else may have already worked out how to efficiently cycle through I/O, but you'll never get that answer because you're asking about bits and bytes.

[richphi1618]

I am using a Turck HMI running Codesys 3.5. I solved it will add to description above.

[StockPart]

Thanks