Octal Button Debouncer

Dan E

Hi,
I was looking for a debounce object in the object exchange, and I saw the Octal button debouncer. I assume from reading through the D8C_BUTEngine that it can handle up to 8 debounce buttons.

I am looking to have six different push buttons in my project, and I wanted each of them when pressed to interrupt the main program to perform their respective function.

Can this program able to do these tasks at any point in time during a main program when pressed?

Thanks,
Dan

Kye

The object just tells you if a button was pressed, the state of the button, and if it was released... If does not execute any special code for you.

Dan E

Hi, I attached a sample code that shows what I am trying to do, but i know these commands may not actually do what I intended.

Thanks,
Dan

Kye

Okay, thats the idea. Read up on what the functions return and take however inside of the button debouncer object. You are not calling them properly there.

Dan E

Okay, I did some updating and reading, is it 'result' that I need to check to be true, i'm not sure how to check each button specifically and if 'result' = true. Maybe do I need to call the function first for each button, then check if 'result' = true?

Here is what I actually tried:

And here is the full code, I added sound to test if the buttons were working or not, using the setup I already had.

debounce test - Archive [Date 2011.01.25 Time 11.20].zip

Thanks,
Dan

JonnyMac

There are times when a debouncing cog is useful but I don't think it's beneficial here -- you can create a simple debouncing method that handles your pins. In this case you can pass the # of [contiguous] pins, the base pin of the group, and the debounce timing in milliseconds.

Simpler is often better.

pub main | btns

  repeat
    btns := scan(6, 12, 50)                                     ' scan buttons
    case btns
      %00_0001:                                                 ' base_pin pressed
        playwav(string("music1.wav")
     
      %00_0010:                                                 ' base_pin + 1pressed
        playwav(string("music2.wav")
     
      %00_0100:                      
        playwav(string("music3.wav")
     
      %00_1000:                      
        playwav(string("music4.wav")
     
      %01_0000:                      
        playwav(string("music5.wav")
     
      %10_0000:                       
        playwav(string("music6.wav")
 

pub scan(pins, base, ms) : debounce | t

'' Active-high debounce
'' -- pins is # of contiguous pins to debounce
'' -- base is the lsb pin of the group
'' -- ms is the debouce timing in milliseconds

   debounce := (-1 >> (32 - pins))                              ' assume active

   t := cnt                                                     ' sync for timing
   repeat ms                                                    
     waitcnt(t += clkfreq/1000)                                 ' wait 1ms
     debounce &= (ina >> base)                                  ' scan inputs

pgbpsu

JonnyMac-

I always love your posts because they are simple, straight forward, clever, and exactly what's needed. This one is no exception, although it leaves me wondering what happens if debounce returns with more than one bit high. Is that even possible if someone were to hold 2 buttons for more than 50ms?

Thanks,
Peter

JonnyMac

Peter,

Thanks for the kind words. You'll note that in Main a case structure is used; you could in fact use this to detect multiple inputs (I used binary to make this easier to visualize). If the return value falls through the case structure without a match then nothing happens. If you want a default action for no match you can use the other option with case.

There is an advantage to returning multiple pins: you could use one as a "shift" key and get 10 sections (five un-shifted, five shifted) from your six inputs.

Keep in mind that the debounce method works by checking which pin(s) stayed pressed during the debounce period, that is, they didn't bounce. In your practical application you may want to allow the audio to finish before rescanning or, at the very least, force a release of all buttons (return of %000000) before going back to the top of your scan loop.

pgbpsu

JonnyMac-

Thanks for answering my question. I'd forgotten that case has a default case. I like your idea if a shift button and with the binary representation for the individual cases, that's a very easy thing to visualize (and code). I'll have to remember this post next time I need button debounce.

Regards,
Peter