Setting bits

[bearpawz]

Thanks for the reply. Actually, I got the displaying the digits thing all set. The display chip is quite handy as it handles all the multiplexing of the digits. Just have to send it what digit to update and then the micro can go do what ever else it needs to do. To rephrase the question , I need to know how to set a certain number of bits in a byte or word variable. For instance if the byte is %00011111, how would I easily set the first 5 bits to on? Since this part of the display shows the bargraph I need to make sure if led 5 is on, so are all the other led's (0-4).

As far as the formula part goes if anyone is following along, I decided Im just going to have to pass in an upper and lower bound to the micro to tell it how to scale the bargraph. So I will just send in an Upper bound of 260, and a lower bound of 100 for the temp display, and then the micro can subtract the lower from the upper and divide by 16.


Resolution = (Upperbound - lowerbound)/16

I know this will give me a resolution of 10 degrees for each LED. Im VERY tired and probably need to sleep.. just cant seem to get the rest of it.

[mackrackit]

I was hoping the part of that thread explaining
~DCD
would help

[bearpawz]

Ok, I kind of see where your going. What I need to do is something very similar. If I understand correctly DCD will set the specified bit. Here is what the help in MCS says:

"DCD returns the decoded value of a bit number. It changes a bit number (0 - 15) into a binary number with only that bit set to 1. All other bits are set to 0.

Example

B0 = DCD 2 ' Sets B0 to %00000100"

Ok, thats cool. And after re-reading that other thread I see where your going with this. Lets say I know my bargraph needs to display 50% or 8 segments. I would need to say something like DCD = 8. This gives me %10000000. So in effect only my 8th LED will light up. My problem is I need ALL the LED's from 1 to 8 to light up... what I need to see is %11111111.

Using ~DCD is ALMOST what I need. For the number 8 I would now have 011111111. Close but not quite. Just for fun, lets say that I really need only 4 led's lit up. (%00001111). Using ~DCD I would actually get %11110111). Do I understand this correctly?

Anyway, now that I have actually had some sleep. I can think a wee bit more clearly. Using the look up table should work, just seems there should be an easier way to do this. For anyone following along I figured out my final formulat. I will need three peices of information: Bargraph upper bound, Bargraph lower bound, and value. (And yes, I have spent WAY too many years messing around with arrays in VB ).

Here is my final formula then:

Bargraph = (Data - LowBound) / ((highbound - lowbound)/16)

Simplest samples to plug in with oil pressure values: Upper is 32, lower is 0. For a presure of 16 (50% on the bargraph) I need to light 8 led's

Bargraph = (16 - 0)/((32 - 0)/16)
bargraph = 16/2 = 8.

So now I just need to tell the pic to light up LED's 1-8 and I am done. Until I get a better lightbulb over my head, Im just using a look up table. then of course, there will be the issue of getting the values IN to the processor.. but thats a whole other war to battle.

[Jerson]

I think you wish to build a bar graph with a value

This will help you

' Build a bar from the value in ChPeak
' Each led gets 1 bit - 0 for on, 1 for off
' Output in BarGraph 16 bits
' Gr[0] is a temporary variable
'
BuildBar:
    for gr[0] = 0 to 15
      if gr[0] < ChPeak then
        ' put this LED off 1
        BarGraph.0(gr[0])=1
      else
        ' put this LED on 0
        BarGraph.0(gr[0])=0
      endif
    next
    return

[bearpawz]

Well that certainly would work as well. Thanks. I was hoping there would be some kind of command like DCD that would just magicaly set all the bits on but I guess not. I might look into just manipulating the bits some how. then again, I havnt looked but how many CPU cycles does the lookup command take? anyone know?

[Darrel Taylor]

No magic commands, but maybe this will do ...
BarGraph is a Word var.

BarGraph=$FFFF<<(LEDcount-((BarData-RangeLOW)*LEDcount)/(RangeHIGH-RangeLOW))

If the BAR is going the wrong way, just change it to shift right (>>).

[Jerson]

Wow Darell, that's an ace. I use this for scaling readings but never thought of it this way. Nice tip.

Superb