how to stop a loop arduino

Question

I have this loop  how would I end the loop       void loop              read the pushbutton input pin          a           Serial println a           analogWrite speakerOut  NULL          if a  gt  50  amp  amp  a  lt  300         analogWrite speakerOut  200                  if a  lt   49           analogWrite speakerOut  NULL                  if a  gt   300  amp  amp  a  lt   2499             analogWrite speakerOut  NULL

User · Accepted Answer

Arduino specifically provides absolutely no way to exit their loop function, as exhibited by the code that actually runs it:

setup();

for (;;) {
    loop();
    if (serialEventRun) serialEventRun();
}

Besides, on a microcontroller there isn't anything to exit to in the first place.

The closest you can do is to just halt the processor. That will stop processing until it's reset.

User · Answer

The three options that come to mind   1st   End void loop   with while 1     or equally as good    while true   void loop          the code you want to run once here         e g   If  blah    blah    etc       while 1           last line of main loop     This option runs your code once and then kicks the Ard into  an endless  invisible  loop  Perhaps not the nicest way to  go  but as far as outside appearances  it gets the job done  The Ard will continue to draw current while it spins itself in  an endless circle    perhaps one could set up a sort of timer  function that puts the Ard to sleep after so many seconds   minutes  etc   of looping    just a thought    there are certainly  various sleep libraries out there    see  e g   Monk  Programming Arduino  Next Steps  pgs   85-100  for further discussion of such   2nd  Create a  stop main loop  function with a conditional control  structure that makes its initial test fail on a second pass  This often requires declaring a global variable and having the   stop main loop  function toggle the value of the variable  upon termination  E g    boolean stop it   false            global variable  void setup        Serial begin 9600          blah       boolean stop main loop             fancy stop main loop function      if stop it    false       which it will be the first time through          Serial println  This should print once               then do some more blah    you can locate all the           code you want to run once here    eventually end by           toggling the  stop it  variable                stop it   true       like this     return stop it      then send this newly updated  stop it  value                         outside the function    void loop        stop it   stop main loop          and finally catch that updated                                        value and store it in the global stop it                                        variable  effectively                                        halting the loop          Granted  this might not be especially pretty  but it also works  It kicks the Ard into another endless  invisible  loop  but this  time it s a case of repeatedly checking the if stop it    false  condition in stop main loop     which of course fails to pass every time after the first time through     3rd  One could once again use a global variable but use a simple if  test    blah    structure instead of a fancy  stop main loop  function   boolean start   true                     global variable  void setup           Serial begin 9600      void loop           if start    true               which it will be the first time through               Serial println  This should print once                          the code you want to run once here                e g   more If  blah    blah    etc           start   false                   toggle value of global  start  variable                                 Next time around  the if test is sure to fail      There are certainly other ways to  stop  that pesky endless main loop  but these three as well as those already mentioned should get you started

User · Answer

This isn t published on Arduino cc but you can in fact exit from the loop routine with a simple exit 0      This will compile on pretty much any board you have in your board list   I m using IDE 1 0 6   I ve tested it with Uno  Mega  Micro Pro and even the Adafruit Trinket  void loop        All of your code here     Note you should clean up any of your I O here as on exit   all  ON outputs remain HIGH        Exit the loop  exit 0      The 0 is required to prevent compile error      I use this in projects where I wire in a button to the reset pin   Basically your loop runs until exit 0   and then just persists in the last state   I ve made some robots for my kids  and each time the press a button  reset  the code starts from the start of the loop   function

User · Answer

just use this line to exit function  return

User · Answer

This will turn off interrupts and put the CPU into  permanent until reset power toggled  sleep   cli    sleep enable    sleep cpu      See also http   arduino land FAQ content 7 47 en how-to-stop-an-arduino-sketch html  for more details

User · Answer

Matti Virkkunen said it right  there s no  decent  way of stopping the loop  Nonetheless  by looking at your code and making several assumptions  I imagine you re trying to output a signal with a given frequency  but you want to be able to stop it   If that s the case  there are several solutions    If you want to generate the signal with the input of a button you could do the following  int speakerOut   A0  int buttonPin   13   void setup         pinMode speakerOut  OUTPUT       pinMode buttonPin  INPUT PULLUP      int a   0   void loop         if digitalRead buttonPin     LOW            a             Serial println a           analogWrite speakerOut  NULL            if a  gt  50  amp  amp  a  lt  300                analogWrite speakerOut  200                      if a  lt   49                analogWrite speakerOut  NULL                      if a  gt   300  amp  amp  a  lt   2499                analogWrite speakerOut  NULL                       In this case we re using a button pin as an INPUT PULLUP  You can read the Arduino reference for more information about this topic  but in a nutshell this configuration sets an internal pullup resistor  this way you can just have your button connected to ground  with no need of external resistors  Note  This will invert the levels of the button  LOW will be pressed and HIGH will be released  The other option would be using one of the built-ins hardware timers to get a function called periodically with interruptions  I won t go in depth be here s a great description of what it is and how to use it

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