Button command Help!

Magicalman

Hello I am very, very new to the Propeller and apologize for such a basic question however i could sure use some direction, I have used pbasic for a number of years but just cant seem to figure this out in Spin

All i would like to do is be able to alternately turn on and off say 8 Led's on p1 through p9 each time i press a button on p0, it seems simple?


I am able to turn the leds on and off using the outa command but just cant wrap my head around how the button loop works in Spin. once again i apologize for the trivial question but could really use some advice !

Mike Green

Think of the BUTTON statement as a specialized form of GOTO that goes one way if the button is pressed and the other way if it's not. Internally, it debounces the button and optionally handles repeated button presses if the button is held down, but you don't see the details of that. If you want to use alternate button presses to turn something on and off, you'll need two BUTTON loops, one to wait for the even time the button is pressed and the other for the odd time for the button to be pressed. When it "falls through" the first BUTTON loop, your program turns something on. When it "falls through" the second BUTTON loop, your program turns something off. Eventually your program does a GOTO to the beginning and it all starts over again.

Magicalman

Thank you very much!! i do kind of get that !! i guess what i need to know is do i keep the button statement in this case "ina[0]" in a "repeat" loop or do i just add it prior to each outa statement !

Ariba

Here is an untested Spin code fragment that should show you how a button press can be detected.
Depending of how you have connected your button you may need to swap the states for pressed (1) and released (0).

dira[8..1] := %11111111
select := 1
repeat
  outa[8..1] := select

  repeat until ina[0] == 1    'Wait until button pressed
  waitcnt(clkfreq/50 + cnt)   'debounce
  repeat until ina[0] == 0    'wait until button released
  waitcnt(clkfreq/50 + cnt)   'debounce
 
  select := select << 1
  if select > 1<<8
    select := 1

To make a running code out of that, you need to add a PUB and declare the select variable (as long).

Andy

Magicalman

Thank you very much Andy!! thats exactly what i was looking for !!! it's all starting to make some sense now Cheers

sam_sam_sam

Thanks for for sharing this code

JonnyMac

Here's a bit of code that I use for debouncing a single input; the purpose of this code is to wait until an input has gone high and stays high for the specified duration; contact "bouncing" is filtered out.

This code is currently deployed in the Buzz Lightyear hand-stamper that will start showing up in Disney parks.

pub wait_press(pin, ms) | debounce, t

'' waits for (active-high) button press of ms milliseconds

  dira[pin] := 0                                                ' set pin to input mode

  debounce := 0                                                 ' clear debounce timer

  t := cnt                                                      ' sync with system cnt
  repeat until (debounce == ms)                                 ' wait specified db time
    waitcnt(t += clkfreq/1_000)                                 ' hold 1ms
    debounce := ++debounce * ina[pin]                           ' scan input

Again, this is for a single input and will not return until the condition is met. The fun is in the last line of the loop: the debounce timing is incremented and then multiplied by the state of the pin. If the pin bounces open (0) then the timer is reset.

sam_sam_sam

Jon

Thanks for share this