Priority Queue with BS2

NZmbe

Is it possible to write a priority queue within PBasic? Honestly I'm not even sure that I'm asking the right question here. Still very new to this realm and I'm hitting walls head on left and right with this project.

The idea is I'd like to take a 9 LED array (3 rows of 3), with one push button per row, and have the order in which a button is pressed show up on the array. Example: When button 'a' is pressed the first LED of its corresponding row goes high. When the next button is pressed (whether it be 'B' or 'C') the second LED for the corresponding row goes High. And the last button would illuminate LED 3.

The reason I ask about priority queueing is when button 'a' in this case goes low, the LED (in the case position 1) should go low and the remaining "high" LED's shift positions to reflect the new order of priority.

Is this type of code even possible in PBasic? Any help would be greatly appreciated.

erco

I think you want each new keypress (of 3 buttons) to light the corresponding LED in the leftmost column and shift the previous entries one column to the right. Is that correct? Sure, easily done in PBasic with a Stamp. You're only using 3 inputs and 9 outputs (a total of 12) so you could even add another column of 3 LEDs since BS2-class Stamps have 16 I/Os.

x=button 0=LED

x oooo
x oooo
x oooo

NZmbe

Right, but thats where I hit the "wall". Thats the first half to this, and like you said, pretty simple. But what if I wanted the columns to shift to the left one position after I let go (open) the first button that was pressed?

So for example

a-c=button LED=1 / 0

a 1000
b 0100
c 0010

then button 'a' is released

a 0000
b 1000
c 0100

Its that shift thats got me stumped

erco

Shifting left? So are you pushing buttons to follow the LEDs, like a game?

NZmbe

erco wrote: »

Shifting left? So are you pushing buttons to follow the LEDs, like a game?

No, actually the opposite. The LEDs need to follow the buttons, following FIFO.

Think of having three boxes in which you are going to place objects in with random order over an extended period of time. You need to know which order the items went in so that they can be removed in order of FIFO (thus three LEDs per box/ button) To keep the cycle flowing without pulling all the items and reseting, you'd want to be able to cancle the 'priority' setting of the item you pulled, and in doing so shift the priority of the other boxes to reflect said action. I know the easiest way to achieve this is to have timers on the boxes but this is not a project based on time sensitivity, just priority sensitive.

erco

I'm missing something. I think you want to indicate which of 3 buttons was pressed in the LED array, but as drawn, the data will need to move to the RIGHT, not left. Each time you press a key, that LED comes on on the leftmost column, and the previous LED in the leftmost column moves to the center column, and the previous center LED moves to the rightmost column.

As you decribed most recently (columns shifting left), older data on the right is moving left toward the buttons. Not sure what that is supposed to indicate or where that data came from.

Am I confused?

NZmbe

I'm sorry erco, I had no intention of making this confusing. Let me try one more time...

'P = Priority Level

'inputs - 'led array
.......'p1 'p2 'p3
IN1 - 0...0...1
IN2 - 1...0...0
IN3 - 0...1...0

Ok so, if this were the real thing, what just happened was IN2 was set High before IN1 and IN3, then IN3 was set High, then IN1 was set High last out of all three. So, by looking at the array we can see the order in which the buttons where pressed. Now, if I were to set IN2 Low, it would turn its corresponding LED low, and shift the other two priority columns like this:

.......'p1 'p2 'p3
IN1 - 0...1...0
IN2 - 0...0...0
IN3 - 1...0...0

Creating what I want to call a cycle although I know thats not PBasic correct. What I mean is, if I were to set IN2 High again it would show up on its row as Priority 3. Creating a cycle of 'priority' commands. If IN3 is set low, then what ever button/s are still set High will shift to accomodate the new priority status.

I hope that makes sence. Thanks again

erco

OK, sounds like you want the most recent entry on the rightmost column, shifting leftward with each new keystroke. That's where you lost me, it just seems a bit counterintuitive.

Still easily done, except I think your expectations on the high/low might need adjusting. If all your switches are normally low, they will momentarily go high when pushed. So pressing a button will instantly light the corresponding LED in the rightmost column, and the previous data shifts left. Nothing happens when you release the button, that just advances the program to the "scan keyboard" portion of the program.

Can you live with that?

NZmbe

Hey, at this point I'm down for anything!

erco

Have you started writing your program yet with your I/O pin assignments? Let's see what you have so far, working or not. This is a learning exercise, right?

RiJoRi

This is an interesting problem!

I thought it over last night, and came up with a "flow sketch."

L1:
    [Read Keys]
    <Keys Changed?>-- No --> goto L1
        Yes |
    <Key Down?>-- Yes --> goto L2
         No |
    [Clear all bits for this
      key in the queue]
             |
    [Crunch the queue]
             |
    [goto L3]

L2:
    [Save the keys in the queue]
             |
L3:
    [Copy the queue to the LEDs]
             |
    [goto L1]

"Crunching" means to remove all '0' values in the queue by shifting non-zero values down.
Copying the queue to the LEDs may need to be done in the L1 section.
The case of one key being down steady as a second key goes up and down needs to be addressed, OR just the changed key will need to be saved to the queue (L2).

HTH,
--Rich

NZmbe

Alright, I've been trying to modify a button scan code I found online and I got a few questions.

I can't figure out how to 'link' the I/O pins to specific constants.

e.g.:
Rooma = dig0todig2
Roomb = dig3todig5
Roomc = dig6todig8

The idea being that Rooma display cant spill into roomb display. I was trying to accomplish this though an Alias/Mod but its not going anywhere. Or, can I make three different counters??? hmmm

Second question: To RiJoRi, thanks for the input! I understand the concept but not the application. Like I said before I'm still very new at this and thus I have no idea how to 'crunch the queue':smilewinkgrin: Are your 'queue' ideas done through Write/Read?

(n00b alert) If I'm running 9 LEDs out OUTH how can I get the remaining LED to follow suit? OUTH=8-15 so how can get out7 involved?

Plus I'm all ears for any other suggestions that you may have.

Thanks again for the help!

' {$STAMP BS2}
' {$PBASIC 2.5}



' -----[ I/O Definitions ]-------------------------------------------------


Segments        VAR     OUTH                    ' output on pins 8-15


Rooma           PIN     0                       ' Room 1
Roomb           PIN     1                       ' Room 2
Roomc           PIN     2                       ' Room 3

' -----[ Constants ]-------------------------------------------------------


Dig0            CON     %100000000               ' segment data for Priority
Dig1            CON     %010000000
Dig2            CON     %001000000
Dig3            CON     %000100000
Dig4            CON     %000010000
Dig5            CON     %000001000
Dig6            CON     %000000100
Dig7            CON     %000000010
Dig8            CON     %000000001

Pressed         CON     1                       ' button states
NotPressed      CON     0


' -----[ Variables ]-------------------------------------------------------

btns            VAR     NIB                     ' button holder
btn1            VAR     btns.BIT0               ' debounced button value
btn2            VAR     btns.BIT1               ' deboucned button value
btn3            VAR     btns.BIT2               ' debounced button value
idx             VAR     Nib                     ' Priority index
counter         VAR     Nib                     ' current priority to display


' -----[ Initialization ]--------------------------------------------------

Setup:
  DIRH = %0111111111                            ' P8 - P15 are outputs
  GOSUB Show_Prio                               ' initialize display


' -----[ Program Code ]----------------------------------------------------

Main:
  DEBUG CLS,
        "Button & Display Test", CR, CR,
        "Rooma (P0).......... ", CR,
        "Roomb (P1).......... ", CR,
        "Roomc (P2).......... "

  DO
    GOSUB Get_Buttons                           ' scan buttons
    GOSUB Show_Buttons                          ' show states
    IF (btns > %000) AND (btns < %111) THEN     ' pressed?
      counter = counter + btn1 // 10            ' increment if Button1 = 1
      counter = counter + btn2 // 10            ' increment if Button2 = 1
      counter = counter + btn3 // 10            ' increment if button3 = 1
      GOSUB Show_Prio                           ' update display
      PAUSE 250
    ENDIF
  LOOP


' -----[ Subroutines ]-----------------------------------------------------

'Show prio via LED

Show_Prio:
  DEBUG CRSRXY, 0, 5, DEC ?counter              ' update DEBUG screen
  LOOKUP counter, [Dig0, Dig1, Dig2, Dig3, Dig4,
                   Dig5, Dig6, Dig7, DIG8], Segments
  RETURN


' Scan and debounce buttons

Get_Buttons:
  btns = %000111
  FOR idx = 1 TO 5
    btns.BIT0 = btns.BIT0 & Rooma               ' scan button
    btns.BIT1 = btns.BIT1 & Roomb               ' scan button
    btns.BIT2 = btns.BIT2 & roomc               ' scan button
    PAUSE 5                                     ' debounce delay
  NEXT
  RETURN


' Show current button states

Show_Buttons:
  FOR idx = 0 TO 1
    DEBUG CRSRXY, 20, 2 + idx                   ' move cursor
    IF (btns.LOWBIT(idx) = Pressed) THEN        ' check and display status
      DEBUG "Pressed", CLREOL
    ELSE
      DEBUG "Not Pressed"
    ENDIF
  NEXT
  RETURN