#define GREEN 7 // Pin 7 is assigned variable GREEN. Global variable. unsigned long mintime = 2000; // Global variable unsigned long maxtime = 5000; // Global variable unsigned long previoustime = 0; // used to reset timer. Global variable. void setup() { pinMode(GREEN, OUTPUT); // Writes code to pin 7 // Serial.begin(9600); // Start up serial monitor, baud rate 9600 } void loop() { unsigned long time = millis(); // starts timer named time. local variable if (time - previoustime >= mintime && time - previoustime <= maxtime) { // if time - previoustime is greater than 1999 and time - previoustime is less than 5001 digitalWrite(GREEN, HIGH); // GREEN turns on } else { digitalWrite(GREEN, LOW); // If not within min/max time, turn LED off } if (time - previoustime == maxtime) { // if time - previoustime equals maxtime previoustime = time; // previoustime becomes time } // time(2000) - previoustime(0) = mintime(2000) :: time(5000) - previoustime(0) = maxtime(5000) // time(7000) - previoustime(5000) = mintime(2000) :: time(10000) - previoustime(5000) = maxtime(5000) // time(12000) - previoustime(10000) = mintime(2000) :: time(15000) - previoustime(10000) = maxtime(5000) delay(100); // delay by .1 second for next loop // delay(1); // If I set delay for 1 millisecond, it works fine. } I made code to turn on a GREEN led on if the time was between 2 to 5 seconds, and then right after the 5 second mark, it would reset the timer. When I use delay(100) the GREEN led did work, but only for 3 times. after that it wouldn't turn on. If I used delay(1) though, it worked for at least 2 minutes. Would the delay(1) have stopped eventually, if not, I would like to know why delay(100) ended the code after only 3 times.

The OP may not be entirely familiar that to mix delay() and millis() in the same code can cause issue. [image] frost_10: if (time - previoustime == maxtime The OP might want to fix that with a if (time - previoustime >= maxtime.

if(time - previoustime == maxtime) { previoustime = time; } This line of code for delay(2500) would only run and update twice in the alloted timeframe(5000), while for delay(100) it would run and update 50 times. Delay(2500) gave me only one blink, while delay(100) gave me 3. So this would seem to indicate that the code in the loop takes no time except for the delay(whatever time), because I would expect the delay(100) to be only 1 blink while 2500 would be 3 blinks. If you do delay(3000) or anything that doesn't fit into 2500 and 5000 nicely, then I do get since that would mean the code would run every 3 seconds. Which would mean the first loop would start off at 0, second loop would start at 3, and third loop would start at 6 seconds. Since my maxtime is 5000, even though Milli() did hit that time, the loop is only for every 3 seconds so that would be way off.

Thank you. I was not aware that doing those together would cause issues. I got rid of delay() and that worked. I also tried keeping dealy and just using >= maxtime which also worked. So I can't use delay() at the end of the loop. However, I can still use delay in a more localised fashion? Say I make a couple of if nested statements and at the end of the last if statement I say delay(). That wouldn't mess with any millis outside of that localised function, right?

I do not use delay() in my code. Using delay mixed with millis() might result in things working well or it might not. You'll have to give it a try and see.

Not sure you understood the point I was trying to make. Checking for the time interval being exactly equal to maxtime, as opposed to >=, will eventually fail. Because of the way millis() is implemented, it will occasionally skip a millisecond, with the millis count incrementing by two instead of one. There is a 1/5000 chance this will happen when the comparison with maxtime occurs. Made worse with the delay(100), since there is a 1/100 change the last millisecond of the delay period will be when the skip occurs.

Hello frost_10 I´m trying to understand the task of the sketch. Should the sketch flash an LED with different times for the ON and OFF states? If so, take a look at the BLINKWITHOUTFELAY example in the IDE and do some modification to the timer.

[image] frost_10: However, I can still use delay in a more localised fashion? Say I make a couple of if nested statements and at the end of the last if statement I say delay(). That wouldn't mess with any millis outside of that localised function, right? As you are yet not so experienced you should not mix-up delay() and millis(). Understanding non-blocking timing and how to avoid each and every delay() requires more than just looking at the classical blink without delay-demo-code. After having understood the real nature of non-blocking coding you wil RE-recognise the principle inside the blink-without-delay-example. In short "BWD" But IMHO only looking at the BWD-example makes it hard to understand the fundamental difference between delay-ing and non-blocking-coding. It is not just a matter of 20 minutes playing around with the BWD-example. Depending on your talent and how long you want to learn on it per day it is realistic to estimate learning the basics of non-blocking coding will take some hours or maybe some days. Me myself I haven't found a textbased online tutorial that would explain it all in a way that with judging with my personal criteria I would say "very well explained" Some parts are epxlained in two tutorials I have written. This is about non-blocking timing [image] Example-code for timing based on millis() easier to understand through the use of example-numbers / avoiding delay() Tutorials non-blocking timing. Execute code only from time to time. There are a lot of different ways to learn programming. This thread wants to add another approach that is different to the yet existing ones. UPDATE 06.01.2023 if you are mainly interested in applying non-blocking timing you can do a quick read of this short tutorial / demonstration If you are intersted in understanding the details how it works go on reading here. I use an everyday analogon in this post to explain the basic principle … This is about state-machines (written by me though not in the quality that I myself would say all details explained in sufficient deepness) [image] A Demo-Code explaining the switch-case state-machine and how to do things (almost) in parallel Tutorials Hi everybody, if you look at the end of this first posting you see a list of links that show where this tutorial was used as a link. Go through this list to find additional information on how to apply this code This democode requires only the pure microcontroller without any hardware. You just open the serial monitor to watch the behaviour of the code. From time to time I enjoy writing demo-codes that want to explain programming-functionalities. There are a lot of different approachs to expl… I have some ideas how to give the overview about non-blocking-coding = multitasking without an RTOS but not yet written. best regards Stefan

Ok. I took out the delay from the code and used serial.println() to see what numbers I got. I saw that a lot of numbers were skipped. For me, it seemed to be usually skipping every 3 numbers. I had 13 zeroes and then 9 ones, then it started counting 4, 7, 10, 14, 18, 22, 26, 30(for as far as I could tell, it counted mostly by 4s after this point, except there were numbers that were maybe 5 numbers away rather than 4). Is this what you were talking about?

The task of the sketch is to turn on the GREEN led for 3 seconds. Those 3 seconds were in between 2-5 seconds, then right after the timer hits 5 seconds, previoustime should reset so it would loop and be able to turn on again for 3 seconds. I forgot about the inbuilt guides, that would have helped me with the const ints and ints and #define, lol. Probably should take a look at them before I play around with Arduino again.

Thank you. I am still pretty new and do have a lot of things to learn.

Not exactly what I was talking about. What you are seeing is the delay caused by the Serial transmit buffer being full. Once the buffer is full, Serial.print becomes a blocking function, waiting for characters to be sent so there will be space in the buffer. Assuming you are using 9600 baud for Serial, each character takes a little over 1mS to send, so there will be a delay of approximately 4mS when printing a 2-digit number (two characters for the number, with another two characters for newline and carriage return).

Need help understanding why code works only a certain way

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frost_10 December 3, 2022, 10:25pm 16

I did no planning before playing with the Arduino. This was the simpliest example of a time diagram I saw online and should work for this sketch.

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