Prop Backpack overlay question

Seeker

I am using the Prop Backpack as a standalone board to read a few sensors and overlay the variables and some text on a screen with a live video feed. I can get the overlay to work fine if I am outputting strings, but I can't figure out how to output an integer variable (bytes, words and longs). I have read through the docs and through posts in the forum but can't seem to find the info.

Of course the search function in the forum is not the best so I might have missed it.

But I swear I have looked... so now I am asking... is there a way to display variables when using the Prop Backpack as a standalone board to overlay onto a video source?

Thanks!

John Abshier

In the Propeller library that comes with the Prop Tool is a file numbers.spin that will convert longs to strings. Sign Extend 7 and Sign Extend 15 will convert byte and words to longs (page 156 of the manual. Numbers.spin is a Swiss army knife object. If you search for number to string (I use Google instead of the forum's search "site:forums.parallax.com number to string" returns 13k results) you may find something simpler.

John Abshier

Seeker

Great! That should work.

I wasn't sure if there was something in the built-in code I could use... I had a feeling there wasn't. But numbers.spin sounds like it will do the job.

And thanks for the quick answer. Now I just have to do a bit of preening to keep the memory footprint down, or compile with BST...

Duane Degn

I didn't see an easy way of displaying numbers in the my copy of the overlay object.

You should be able to use a "Dec" method from one of the serial objects to output numbers.

Here's PST's Dec method adapted for the Backpack.

PUB Dec(value) | i, x{{Send value as decimal characters.
  Parameter:
    value - byte, word, or long value to send as decimal characters.}}


  x := value == NEGX                                                            'Check for max negative
  if value < 0
    value := ||(value+x)                                                        'If negative, make positive; adjust for max negative
    print("-")                                                                   'and output sign


  i := 1_000_000_000                                                            'Initialize divisor


  repeat 10                                                                     'Loop for 10 digits
    if value => i                                                               
      print(value / i + "0" + x*(i == 1))                                        'If non-zero digit, output digit; adjust for max negative
      value //= i                                                               'and digit from value
      result~~                                                                  'flag non-zero found
    elseif result or i == 1
      print("0")                                                                 'If zero digit (or only digit) output it
    i /= 10                                                                     'Update divisor

Just paste the above method into the overlay object. I haven't tested it but I'm bet a QuickStart label it works.

It assumes there's a method "print" that allows characters to be displayed on the overlay. The above code should also work if the method "out" is used instead of "print".

Seeker

Duane Degn wrote: »

I didn't see an easy way of displaying numbers in the my copy of the overlay object.

You should be able to use a "Dec" method from one of the serial objects to output numbers.

Here's PST's Dec method adapted for the Backpack.

PUB Dec(value) | i, x{{Send value as decimal characters.
  Parameter:
    value - byte, word, or long value to send as decimal characters.}}


  x := value == NEGX                                                            'Check for max negative
  if value < 0
    value := ||(value+x)                                                        'If negative, make positive; adjust for max negative
    print("-")                                                                   'and output sign


  i := 1_000_000_000                                                            'Initialize divisor


  repeat 10                                                                     'Loop for 10 digits
    if value => i                                                               
      print(value / i + "0" + x*(i == 1))                                        'If non-zero digit, output digit; adjust for max negative
      value //= i                                                               'and digit from value
      result~~                                                                  'flag non-zero found
    elseif result or i == 1
      print("0")                                                                 'If zero digit (or only digit) output it
    i /= 10                                                                     'Update divisor

Just paste the above method into the overlay object. I haven't tested it but I'm bet a QuickStart label it works.

It assumes there's a method "print" that allows characters to be displayed on the overlay. The above code should also work if the method "out" is used instead of "print".

Actually, this was my original fallback plan... or something similar. I had looked at the PST code briefly and thought I could adapt it if I had to.

I will try both and see what works best.

Thanks again to both of you!

And I am still open to any other suggestions if anyone has any. One thing I have learned is that there are many ways to accomplish the goal. Half the fun is finding the one you like best. And it is a GREAT learning experience.

Seeker

I tried both... but Duane, you owe me a Quickstart. I think the limitation is in the "print". It is just a "send literal string", not really a print. And "out" is a single character. More used for sending commands from what I can see. If I worked at it, I might get it figured out... but then I would need to figure out how to break up large numbers for better formatting.

Numbers.spin seems like the best bet for me. I like that I can alter the format for larger numbers, and since I will be adding a GPS, this will come in handy. The only problem is it comes with a lot of "baggage". But in BST I can save 256 longs. If I edit it I am sure I can get that in the Prop tool too.