Retriggerable One Shot.......

Jeff2

Is there A way I can program, A Retriggerable One Shot, on the Propeller Chip? So I can adjust the RC Time. To turn on A Led, for A given time, and if the input pin is
still pressed (on and off) the led will stay on.

kwinn

Loop:
Read push button input pin
if button pressed turn led on
else turn led off
wait retrigger_time

Jeff2

So something like this.


repeat

dira[noparse][[/noparse]6] := 1
dira[noparse][[/noparse]21] := 0

outa[noparse][[/noparse]6] := ina[noparse][[/noparse]21]
waitcnt(clkfreq/4 + cnt)

Jeff2

If you can help me get started
with the program

Peter Jakacki

A "retriggerable" one-shot is not just a simple trigger then delay as the contributed examples shows, it must restart the one-shot on a trigger even if it is already triggered, hence retriggerable. Is this the type of action you want?

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*Peter*

Jeff2

So how do I make the program for
the hence retriggerable?

Jeff2

Here I A circuit, is there A way that it could be programed into the Propeller Chip. So when the input is toggling, the output would be on?

I have A Attachment on the circuit.....

Jeff2

I guess this can't be programed on the Propeller Chip..........A Retriggerable One Shot

kwinn

Jeff2, sorry, lost track of this post. The prop certainly can do this. Slight change required.

Loop:
Read push button input pin
if button pressed timeout = retrigger_time + cnt
led = on
if cnt > timeout
led = off

All you need to do is translate that to spin or pasm.

Peter Jakacki

Yes, back to your post Jeff, being a forum threads do get pushed down the list and sometimes it's just not convenient to answer although you have to admit you had already received some help anyway.

The problem I have with your question is that on the one hand it is very simple yet on the other it depends how you want it to integrate into your program, there are so many ways and we don't have any details of your program.
I personally would not have a program stop just to handle a button but with so many cogs that might be ok for some.

What I normally do for these types of inputs and timing functions is simply to have a Spin/PASM function running in it's own cog that does nothing else but maintain some software timers, both countdown to zero and countup, The function usually handles specials as well as such things as button inputs and so on. Implementing a one-shot here is nothing more than reloading a countdown timer on a condition, while the counter is non-zero the output is true.

A code snippet for detecting that the button "is" pressed and retriggering the "one-shot" (the functions repeat loop cycles through the soft timers and decrements those that are non-zero)

ifnot ina[noparse][[/noparse]button]      ' is button input low? (same as saying "if ina[noparse][[/noparse]button] == 0")
    timer[noparse][[/noparse]0] := 500            ' reload timer 0 for 500ms

and a snippet as to how the led would work in the timer function so that it would light while the "one-shot" was active.

outa[noparse][[/noparse]led] := !timer[noparse][[/noparse]0]      ' turn on active-low led if timer 0 is non-zero

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*Peter*

Jeff2

It has been A long time, that I have made A easy Program. So would I write it like this?

I want to use (Pin23, as the Input switch) and (pin15 of the led)





PUB Led Retriggerabel One Shot


ifnot ina[noparse][[/noparse]23] ' is button input low? (same as saying "if ina[noparse][[/noparse]button] == 0")
timer[noparse][[/noparse]0] := 500 ' reload timer 0 for 500ms

repeat
outa[noparse][[/noparse]15] := !timer[noparse][[/noparse]0] ' turn on active-low led if timer 0 is non-zero






I am bad, I CANT' REMEMBER HOW TO WRITE A EASY PROGRAM........

Peter Jakacki

Since these timing functions are fairly common I have written a small demonstration object that you can incorporate into your program. Include a reference to this in your OBJ section and in your initialization just say:

OBJ
timing : "background"

pub main
background.start ' startup background timing functions

So with this object you should never have to stop and wait for any events as long as you use the various timers all you need to do is load them up with an appropriate delay and then poll them for when they are zero, much like the example in the user processes section of the object itself.

If this looks a bit daunting then maybe you should post your code so I can show you how to incorporate it.

{  background.spin

          **************************************
                     BACKGROUND TICK
          **************************************
                    Peter Jakacki 2010
          **************************************

Purpose:
Implement an "interrupt style" background tick which maintains soft-timers and handles
other low priority events so as to take the load off the main program from having to time
events such as button presses or led blinking etc.

Implementation:
In this semi-purpose object soft-timers are decremented the equivalent of every 1ms until
they are zero. The main program can load these timers and check when they are zero to take
appropriate action. User routines may also be added to suit.

Resources:
cogs:           1
variable:       36 longs
program:        29

Limitations:
As a high-level function this Spin object cannot be called too fast so the minimum is probably around 1ms.
A consequence of trying to go too fast will cause waitcnt to miss the cnt until it cycles around again (~65secs)
}

con

' these clock constants are normally part of the main program
' but are included here for testing
  _CLKMODE = XTAL1 + PLL16X
  _XINFREQ = 5_000_000
  clockfreq = ((_CLKMODE - XTAL1) >> 6) * _XINFREQ


' object constants
  _1mS          = clockfreq/1000                        'Divisor for  1 mS
  prescaler     = 5                                     'prescaler from 1ms tick (5ms)
  timers        = 4                                     'number of soft-timers to support

' user constants
  button        = 0                                     ' demo button input - active low
  led           = 1                                     ' demo led output - active low
  status        = 2                                     ' demo blinking status led

var
  long  bgstack[noparse][[/noparse] 32 ]
  long  timer[noparse][[/noparse] timers ]

pub start
   cognew(Background,@bgstack)


pri BackGround  | i,intv
' user inits
  outa[noparse][[/noparse] led ]~                    ' led off
  dira[noparse][[/noparse] led ]~~                   ' led output
  ina[noparse][[/noparse] button ]~                  ' button input

  dira[noparse][[/noparse] status ]~~                ' using status led
'
  longfill(@timer,0,timers)
  intv := cnt
  repeat
    ' synchronized interval wait
    waitcnt(intv += _1ms*prescaler)

    ' update soft-timers
    repeat i from 0 to timers-1
      if timer[noparse][[/noparse] i ]
         timer[noparse][[/noparse] i ] -= prescaler

    ' user processes etc

    ifnot ina[noparse][[/noparse] button ]           ' is button input low? (same as saying "if ina[noparse][[/noparse] button ] == 0")
      timer[noparse][[/noparse] 0 ] := 500           ' reload timer 0 for 500ms

    outa[noparse][[/noparse] led ] := !timer[noparse][[/noparse] 0 ]      ' activate led while timer0 is active

    ifnot timer[noparse][[/noparse] 1 ]         ' status led
      !outa[noparse][[/noparse]status]
      timer[noparse][[/noparse] 1 ] := 200           ' this timer could be loaded from the main program instead

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*Peter*

hover1

Link to easy programs:
http://forums.parallax.com/showthread.php?p=617192
PS..Stop with the capital "A", it's annoying.
PPS..If you keep the thread in one place it might get answered more often.

Jeff2 said...




I am bad, I CANT' REMEMBER HOW TO WRITE A EASY PROGRAM........

Jeff2

I have two input's, (22 and 23) I want one as, One Retriggerable One Shot, the other one as A on off switch. How do I go about adding the Retriggerable One Shot,
to the Program, so I can adjust the Time.

con 

 _clkmode = xtal1 + pll16x
 _xinfreq = 0_500_000
 
pub Kid
'dira[noparse][[/noparse]0..19]~~

repeat

    if ina [noparse][[/noparse]22] ((((the input one pin22, need's to be  Retriggerabel One Shot, how does the progarm have to look?))))))
      right
    if ina [noparse][[/noparse]23]
         left
  
  
          
pub right
        dira[noparse][[/noparse]0..19] := %11111111111111111111
        outa[noparse][[/noparse]0..19] := %00000000000000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000000000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000010000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000110000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000001110000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000011110000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000111110000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00001111110000000000
        waitcnt(clkfreq/4 + cnt)

pub left
        dira[noparse][[/noparse]0..19] := %11111111111111111111
        outa[noparse][[/noparse]0..19] := %00000000000000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000001000000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000001100000000
         waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000001110000000
        waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000001111000000
         waitcnt(clkfreq/4 + cnt)
        outa[noparse][[/noparse]0..19] := %00000000001111100000