Loop is have it perform a task once have some tasks written inside the void. Loop brackets perform that task once and then in a sense, get out a void loop so that it doesn’t endlessly repeat that task over and over and over again anybody who’s watching this videos probably experienced something like this say. I want the sentence to print once so. I’Ve put the serial print line command inside the void loop I’ve. Given it a delay, I’ve only entered one line of code. I’Ve want it to do this one time so I’ve entered it once well. When I upload this code, what happens? Well, let’s open the serial marker I’ll be printed 100 ups, oh no! I wanted it to print once what is it doing, it’s printing it over and over and over again and that’s, exactly what I didn’t want to happen. So how do we stop that? How can we control if I want something to print once or I want a countdown to go through from ten down nine eight, seven all the way to zero, and I want that to happen one time in the program. Well, the first option is, we can just take whatever commands. We won’t execute it one time and just place them inside void, set up and leave void, loop completely empty there’s, no problem, leaving it empty just empty, and then we can upload this code and check the serial monitor, see what happens. I want this sinister probe once and it dia, so all that we’ve done is basically place the code that we want to execute one time inside the very function that’s made to execute code just one time at startup, namely the void setup.
But what happens after is perform this task and void setup. Well, the Arduino keeps going, it goes, the void, loop and since void loop is empty. It just infinite it’s in an infinite loop of doing nothing. That’S what’s happening right here, so you’ve basically had the Arduino perform some tasks and then kicked it off into an endless loop, which is perfectly fine, there’s, nothing wrong. With that microcontrollers don’t mind being in an infinite loop. There is no operating system, so there is nothing to return back to so it has to do something so it’ll spin itself in an endless loop. But what if we wanted to give it actually control would loop itself like say if I want to have this sentence printed once let’s cut it and then paste it inside the loop again say I want some tasks to be performed. One time this sentence is just a stand in for whatever group single task for multiple tasks, one would like perform two one time. What is this tighten that up and what, if I do, need to be accomplished inside void, loop, well think about what happened when we placed it up in void setup, we place the sentence inside void setup. If printed once, then it moves to void loop and it spins in an infinite loop. Well, couldn’t we just construct an infinite loop at the bottom of void, loop and then have the Senate print once and then pitch it off into that infinite loop.
Absolutely you can do it using this sort of idiom in the C language known as an empty for loop, that it has no initiation point no test and no increment or decrement, and then it’s brackets are empty. Just to note that you could say empty using the multi line, comment, structure and then well does this work. Are we uploaded same check the serial monitor, yeah? I wanted it to prevalence and it did, but is this the only way to keep the Arduino in an infinite loop? No way there isn’t there’s at least two others? You can go wild and then say one and then have it empty. You can use in what’s known as an empty while loop and what happens with this while control structure is as long as its condition is true. It’Ll do whatever’s inside its brackets endlessly, and this is the trouble while loops most of the time as you’ve got. To remember to update some counter variable in the back end and the bottom end of a while loop or either you’ll be pitched off into an infinite look, especially when you’re doing programming in the C language or C or Python, etc, etc. You have to be sensitive when you use while loops, because they can be kind of dangerous where you have to hard stop the program if you pitch it into an infinite loop. Well, in this case, we can use it in microcontroller scenario to our advantage and actually have the Arduino do some tasks.
I mean this can be multiple tasks, I mean we could have serial count. One I don’t know. Cats are great whether one agrees with that or not and etc, etc. We could basically have blah, however much blah we want to occur before that wild one will only occur one time so just to test that and upload and Joe Mauro yeah. I want the center sprint once cats are great now at this point, what’s happening with the Arduino it’s spinning itself in an endless loop. So exactly what it’s doing, which is perfectly fine, because, as far as all outward behavior goes, what we really care about. It’S did what we wanted it to do and then it stopped it stopped and scare quotes it. Didn’T stop doing everything it’s still spinning right here, but it stopped every it stopped at the point we wanted it to so we have ultimately total control over wind void. Loop stops that empty for loop. We just discussed in this while one of it, while true, will also do the exact same thing. We can change this around. Just a verifier puppies are great upload the code and then verify through the serial monitor. Well. Listeners friend wants puppies are great, so this sort of casting void loop into an infinite loop at the very bottom like there’s the closed bracket. The void loop will give us the ability to do whatever task. We want it to run through one time and then it throws it into an infinite loop, that’s three different styles of infinite loops, just show them one more time have an empty four.
We can have while one of empty braces or you can have wild true eat. Any of those three will work and there’s, probably tons more. The C language is known for being able to do really neat things, these sort of idioms of the same language so that’s. All one has to do to be able to stop the void loop at the bottom and caste are doing them into an infinite loop. But if we want to be able to have in a sense a little more technical control over that, what if we want to vary, whether it goes into an empty or an infinite loop or not, based on something that occurs prior to that? Well, can definitely do that too, and this is the option that I tend to prefer. I tend to like to write games with where the Arduino is, where there’s a single player and their request Arduino is requesting moves in the game. The player enters. Those moves. Person plays the game, they either win or lose, and then it asks do you want to replay the game and based on their answer to that question. It either restarts with loop or it halts it or if well it puts it in another form of infinite loop. At least so, how would we do something like that? Well, we can do the global variable of the boolean time. Let’S use it so that we’re thinking more in terms of a game, we’ll say the replay variable and let’s set this variable initially to true and note what a global variable this is going to sculpt over everything that comes up a lot so in inside would look What we can do is test.
We can use an if control structure. We can say if we play double equivalence. It’S true, then do something like in here play the game, and then, after the person finishes playing the game, we can do a request. Like do you want to play again? Have that have a sentence to that effect, sent to the serial, monitor and then have the other sorts of serial available functions, catching the users and the players answer and then, depending on whether they answer whether he or she answers? Yes or no, we can toggle or keep the replay value the same let’s say we toggle it the faults so replay it using as false and then close down void, loop or that bracket, and so just so, we can see this say serial arm I’m totally with It this should just print once I’ll see if it does upload enjoy the game if printed just once. Why? Well, because what happened is initially we have. The replay value set to true it goes through set up hits void, bloom says, is it test is what is the value of replay? Well, if it happens to be true, then print that sentence and then after it exits the if the replay, which is a global variable, keep in mind, the value has been total defaults. So as soon as we talk about here to false it’s changed to false up. Here on this on this bottom pass, and so when it loops back around when void loop comes back around replay is no longer equal to true, so it stops, but it doesn’t, really your Arduino doesn’t stop doing anything.
No it keeps checking basically polling is replay. True, is it true, is it true, is it true and given that it’s been toggle defaults, no it’s, not true anymore, so it’ll never kick back into the loop, it will never repeat, but you can control back. I mean in I’ll have a more videos, video tutorials about the code involved and actually toggling this value based on user or player input, but that’s the simple structure. This is my preferred structure. This is the preferred way Miette for me at least, prefer this method or technique just set up a global variable, a blend type have it set to true or false, depending on how you want it to play out in the hand, have void loop begin and immediately Drop into a if test and then have something occur inside that if tests whatever I want to happen, one time through and then at the bottom toggle the value defaults and that will basically it forces void loop to act like setup, except the beauty of this structure Is that you could add more control code in here and actually have a person control, whether this value toggles, false or true? And if you you know in case you want it to run again, you could have it toggle true and then, when it comes around it’ll play it again, just to see that all that would have to happen. Let’S just set it to true this sentence: will print let’s put a delay in here, so we’re not wiped out with it on the serial order, so every half second enjoy the game should play on the serial, monitor cerium our enjoy the game.
Every half second see so all you need is code to control the value of replay which that’s pretty simple, that’s, just more ifs and more testing. Now there is another option: there’s actually more than any more options but say someone wants to create a kind of fancy. Stop the void loop function, that’s totally possible to you just to be consistent with something like that. Let’S rename our global variable say we want to have a bull in a stop it variable and set it to false. So this is saying: do we want to stop it? No, and all we would need, is to create just a function that returns updates to the stop it variable, so we can have given that we want it to return a boolean type value so stop. This will be, we can refer to this as the fancy stop main loop function. This isn’t really the with the method that I would pick, but it does work. So what just one do well you’re, basically going to do that same sort of if structure inside this let’s take let’s clean out, void loop just so this isn’t too confusing. So we have empty void, loop and we’re. Just building a special purpose. Stop main loop function. What we’d want it to do is every time it’s called we’d want to test that stop it variable. If stop it equals false, namely the users we don’t want it to stop the main loop to stop, then do something so let’s say serial one.
Just so, we know we’re inside the stop function, and then we can at the bottom of that condition, do something very similar. Just like we did before. We can say, stop it equals true. So after we do whatever happens inside the, if we toggle the stop it value and then just to cover all bases, because sometimes modifications inside a function that you’ll create variables that you think they’re global but they’re really not, and to avoid all that you can just Return, whatever the updated value of stop, it is so return stop it, and this will effectively shove the updated value outside of the bottom bracket to the stop and main loop function. And then all we have to do is inside a loop. Have the same. Stop at variable stop. It is going to be equal to well, whatever the value the updated value was ejected by the stop main loop function, so whatever this return value happens to be so, in this case, stop it’s going to equal, true, so it’s going to return that value, namely true, So this is going to in the sense, be replaced with true, so stop it’s going to equal true and then it will hit the bottom of void loop. But this is going to force that value to toggle at the global level and then, when all of this rolls back around stop it won’t be equal to faults anymore, and this sentence won’t run again, so we can test it just to make sure this is the More complicated way to do it, but for a person coming from using other sorts of programming languages that likes building little functions, see inside the stop main loop function, and it only executed one time and at this point what is the Arduino doing? Well, it’s come it’s continuously rolling around checking that condition, and it just so happens that that condition is true, so it never executes this line of code again and that’s.
Just to sort of fancy stop main loop function, that’s one way a person could go about stopping the main loop using a specially created function to do it, like I said earlier, this isn’t my preferred method, but it does work it just it tends to use a Little more bytes to because every function call takes a little more bias than just using a overarching if structure inside a void, loop itself and doing away with this. But no memory is always a concern and the Arduino contacts Ram is at least so. But this is an option now one could also as a final sort of humorous option. Let’S, take this out, take this out of main loop and take this away and say that you want they are doing able to do something just one time and then say: stop everything like cut its power off. Well, all you would need to do is have code so put whatever code. You want performed once there and then under here have say a servo lip power to our switch and have a switch built into the power cable for the arduino between the arduino and the battery and then at your very last command and void. Loop is have that server pull that switch open, that’s, why you could do that, but then you kind of are in a bind you’re going to manually flip the switch by but that’s. One way to do it. Another way would be have some sort of latching relay set up.
I’Ve done this myself, where you have say a security system that you’ve built for your home or your workshop or whatever just playing around with the arduino and you have it consistently checking a whole bunch of sensors, the whole bunch of proximity, sensors, etc, etc. And then, once a person pushes a button on the outside or their fingerprints, recognized or whatever you have, the very final command on void. Loop it’s, like it’s, continuously checking their sensors checking their sensors, and it ignores this value until some other external event occurs, at which time it flips a latching relay that cuts the power off the arduino and then turn the whole security systems. Disabled that’s also an option. Just something to think about there’s an interesting, really humorous discussion about all these various ways of even in a really humorous one. So you could have it have a servo and drop a hammer on top of the Arduino or whatever that’s the beauty of the Arduino. Is you can control the external world and all you have to do is control the power to the Arduino as it’s very last command inside point loop, that’s always an option. Well, I just soon as you power back up it’s going to start that loop all over it down until whatever value is toggled to trigger these other Vance. But Oh discussion of these various ways of stopping that pesky endlessly repeating main loop.
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Originally posted 2015-11-13 23:42:37.