StefanL38 April 23, 2023, 7:09am 6. The code uses millis () function of the Arduino to calculate the time, the millis () returns the time in milliseconds passed since the board is ON. 096 KHz. I need it to turn on for 3 second when the button is pushed briefly. When the maximum number is reached ( 0xFFFFFFFF) and more time passes, it will roll-over back to 0 ( 0x00000000) and start again. I thank you all. OS, IDE, and SDK. initialize the OLED Display and start displaying the measurement as zero. DrAzzy July 25, 2016, 4:15pm 3. As soon as I make power reset arduino again works great. The return value for millis() is of type unsigned long. A Patient Beats Per Minute Heart Rate Monitor This blog is part of a blog series for the Summer of Sensors -- Under Pressure Design Challenge. ( millis () - timeValue ) equals elapsed time from setting timeValue = millis (). Controlling Millis () Using Arduino Programming Questions. Perhaps its named pausedTimestamp. e. Here’s the circuit diagram for this example. If my counter goes to 16 and then I press reset through pin 7, I will get 0 6. Powering down the board. The solution that I used to avoid the rollover issue was to make my own replacement for millis() that returns a "unsigned long long int". Picture 3: Button Wired with Internal Pull-Up (Blue wire connects to Pin 12 of the Arduino) It only takes a small change in the code to turn on these incredibly useful internal pull-up resistors. Delay wont work, it will ruin my Pulse In reading. With the standard number of CPU cycles needed for the ADC conversion (ADC prescaler=128 multiplied by ADC clock cycles=13),. We mentioned one caveat with these functions, and that is that millis() and micros() overflow after around 50 days and 70 minutes, respectively. At 8MHz, after a few minutes, the LED driven with millis () is visibly behind the hardware-driven LED. The Arduino MKR Zero is a development board for music makers! With an SD card holder and dedicated SPI interfaces (SPI1), you are able to play music files without extra hardware. The millis () function is one of the most powerful functions of the Arduino library. This is done by constantly loading the time with the value of millis so the *difference between them * (millis () - yourTimer) is zero. As soon as I make power reset arduino again works great. you can either write 4 custom timers that will either all record the same beginning time then print as each finishes. This number will overflow (go back to zero), after approximately 50 days. 0 License. The library makes use of the timer 1 to send data. When that while loop is finished, you are at the end of loop and then loop starts again from the beginning and eventually setting loopCounter back to 0 on line 137. Wouldn't it be more useful if it gave the actual time of day? For example, you've designed a digital clock program and uploaded it to your Arduino. When that while loop is finished, you are at the end of loop and then loop starts again from the beginning and eventually setting loopCounter back to 0 on line 137. 535 seconds but I wouldn't push that last 35ms or really past 60 seconds. Share. d=2000ms. Nothing else in my code is timer sensitive, so I'd just as soon reset millis() to zero just prior to my need of adding 1000 to it, ever time. system October 9, 2008, 9:15am 1. Follow answered Apr 7 at 18:10. I increase by +1 each time I get a pulse. This function will return timer structure if configuration is successful. I'm trying to display a timer which counts up to 70seconds however once it reaches 65, it restarts (loop). My guess is it will be about as deadly as the Millenium Bug turned out to be - but you won't find out until next year now. arduino. Main Features. Although if you really want to slam the millis() clock back to zero: /* * Code to Reset the millis counter back to 0 * NOTE: this does not reset the hardware counter and * also does not set the software fractional value as that was declared static * in wiring. You will probably want to do something to stop the counter when it hits zero. So the easy way to get a correct millis() count and correct Serial. If analogread bigger than 600, then digitalwrite 13, high. The MKR Zero board is a great board for getting started with various music projects. Here’s the code. Follow. arduino. Using board reset button that resets program & all values to it's start wont help. tomstell July 9, 2019, 1:57pm 15. int MotorControl5 = 5; // Arduino Pin to control the motor. Nothing if you just wanted to see if a period ha passed. You can use millis() to count one day (or maybe one week) and at that point of time reset the board programmatically. I've looked on lots of forums and have tried a few. The Arduino programming language. I will describe the implementation and testing phase of my prototype. This is what i'd like to happen. g. Right now in your code currentMillis is set at the start of each loop, don't do that, do it once in setup. The use of millis() throughout this post is interchangeable with micros(). Perhaps its named pausedTimestamp. I used the 16-bit unsigned int in my millis_overdone. Project Overview. Using Arduino. So, is it so horrific that I reset the millis()?The "millis()" function starts the timing after Arduino started. 0 software - I guess this was fixed and millis() now do really rollover only in 50 days, like it is said in documentation. That is as easy as changing:If we have been up for at least an hour, then print out the number of miliseconds we have been up divided by 60 - but modulo 60000, so if we have been up for 60 hours then start again from zero. system December 18, 2018, 7:36am 1. Step 1: Project Objectives. It just returns a copy of a global variable ( timer0_millis) which is updated by a timer interrupt. I wrote a program for Arduino UNO with attached Funshield, which will animate the following pattern on the four vertical LEDs. 71 days) the timer wraps round to zero and this is the Arduino millis overflow problem. The time is. To state it another way, the value that is returned by the function millis () is the. Share. millis() is incremented (for 16 MHz AVR chips and some others) every 1. 1. robtillaart March 28, 2012, 5:04pm 3. So I built a timer that runs off of the millis command, over the course of 4 weeks it gets off by 15 seconds so its A ok in my book (the interval for millis is 997 actually) But so now I'm wondering. I have been searching all day long for there seem a problem in my coding. Programming is via a USBtinyISP. Use the millis () Function to Check the Time Passed in Arduino. , Case 2 , Case 3 and Case 4) back to accessory mode(i. I’m totally new to Arduino and code, I would appreciate some help. There's no way I could write anything here that would compare. It does however turn out that functions like millis() and Serial() internal settings are determined at compile time. c=500ms after b. If I press a second time reset millis ( millis. setCursor (3, 0); lcd. When checking for elapsed time always use the construct "millis () - lastTimeChecked >= elapsed time". Additionally, we have added reset function too. Reset millis (); Using Arduino. By using a delay (0) the author thinks they are saying "I don't want to delay here, but if anything is using the yield () function it can run now. If the state is LOW and has not changed, I want it to automatically switch to high (ie: shut off the lights). That is what the buffer on the bottom of the circuit is for, to convert the push-pull output of the 555 to open-drain. timer0_millis = 0; // reset millis, will eliminate this in future startTime = millis. This function is used to configure the timer. This number will overflow (go back to zero), after approximately 49 days. Using elapsedMillis makes this easy. Implementing Multitasking with millis () Arduino Millis Example. Delay (traditionally) has two functions that it performs: Wait for a period. c=1000ms. 024 milliseconds, then incrementing by 2 (rather than 1) every 41 or 42 ticks, to pull it back into synch; thus some millis () values are skipped. I made a condition which requires simultaneous button presses. Syntax. To solve it, write rollover-safe code. For accurate timing over short intervals, consider using micros (). So you can count on the time and perform certain tasks after a certain time. Then in the loop we’re going to use the Serial. unsigned char - unsigned char = int. 024 milliseconds, then incrementing by 2 (rather than 1) every 41 or 42 ticks, to pull it back into synch; thus some millis () values are skipped. Regarding the energy consumption of the CPU running your code, the only way to be energy-efficient is to have it sleep most of the time, and wake it up only when there. println () how many decimal places to print. The code for detecting the reset condition is working, but the "reset function", that I copied from the AVR boards, freezes the Zero board: void (* resetFunc) (void) = 0;//declare reset function at address 0. What I want to do is to constantly poll the digitalRead of GPIO_0 and GPIO_2 for a period of one hour. LMAO! Wawa November 21, 2018, 8:26pm 27. Using 16 bits of millis () you can time up to 65. The reset to zero is not a problem if you use millis() properly by which I mean you use subtraction of period start time from current time to determine whether the required period has elapsed mllis() returns an unsigned long, but the reason why the reset to zero does not matter is easier to understand using smaller numbers such as 0 to 255. So, long answer short (no pun intended), you reset millis () by directly setting the variable that millis () uses to keep track of clock cycles to zero. marco_c January 8, 2020, 5:45am 2. This tutorial will explain how you can use micros () and millis () to get more PWM pins on an Arduino Uno, Nano, or Pro Mini. millis () is the same. Reset the flag to false at the start of loop. I am sorry for wasting your time but also want to thank. Example: unsigned long startTime = millis (); Since there are 2^32 bits in an unsigned long it. Bacause depending on what you are doing with millis(), and what board you have, you can make your arduino do weird things after it fills up the memory with millis(). Use case statements for your LEDs. You set RS1 = 0 and RS2 = 0 (see page 13 of the datasheet you provided) and INTCN = 0 (page 9). Save the value of millis () when the timing period starts and determine that the timing period has elapsed by subtracting the start value from the current value returned by millis () and compare the result to the required period in milliseconds. you don't get every millisecond in the draw cycle, because each program cycle needs more than a millisecond. millis() is incremented (for 16 MHz AVR chips and some others) every 1. I'm trying to use millis () to replace a few one-shot delay uses in my code, but first I need to grasp this simple concept. Run multiple if else simultaneously with millis. With a 16MHz system clock, the two LEDs stay in sync indefinitely. arduino programs are standalone programs without os. Milis count the time since the program starts. Arduino Timer count resets at 65 but it should reset at 70. The millis() function outputs a value of 10,000, which is stored in the lastDebounceTime variable. This sketch subtracts 4,294,967,295 from 1. All that happens, on a timer overflow, is that it goes back to zero and starts counting up again. . In mode 1 (Auto Mode), it turnes on and off based on the. No. If output pin 13 high, then capture how millisecond until the pin 13 goto low. When I calculate it and convert it in terms of seconds, I get the operating time is up to 50 days ,approximately. 712 2 2 gold badges 6 6 silver badges 12 12 bronze badges. Now, you can design your program as follows: (1) Keep your lamp at OFF position. Save the value of millis () when you want to start the timing period then each time through loop () test whether the required period has elapsed. arduino programs are standalone programs without os. Then yes, my answer in reply #1 is the issue. Please note that the return value for millis(). print ("Time: "); time = millis (); Serial. Code samples in the. Once a button is pressed (may need to include debounce code), it will switch the case and start the timer (RCT, dont use delays). I'm trying to use millis to hold a pin LOW for a minimum amount of time. println("10 seconds has passed. 024 KHz. #include <LiquidCrystal. 2. millis () just uses Timer 0 overflow counts. It is possible to serial print how milliseconds every output high. Anybody able to help me. 999 Second day 86400000 = Uptime 1 days 00:00:00. I somewhere heard that it could work even in power-save mode but thats not important for now. While studying how millis () and micros () in the millis () function which causes the returned millisecond value to incrementally drift 296us / ~71 minutes (2^32 us) of operation. A boolean is handy for doing this. Hi, I'm trying to use millis() as a delay/timer which is triggered after an event happens. From then on the code works fine. The text of the Arduino reference is licensed under a Creative Commons Attribution-ShareAlike 3. Here's original code: #include <Wire. Removing power also works. This leaves 155 that needs to be subtracted from the maximum value and 255 - 155 = 100. E. However, the current problem is that the start time is being determined on upload/reset to the board and not being. When you stop resetting the timer the value of millis () - yourTimer begins to increase. millis () [Time] Description. The clock on the wall keeps ticking (with millis, it only rolls over every 49 days, and there’s ways around that)That's the idea - the original poster wanted a timing pulse that reset every day to zero - the modulo (%) was one way to provide it. Arduino Forum HELP. If you look at the code that gets slowly typed over the first four minutes of the video you referenced you will see that he sets 'cur_time' to millis () - pre_time and sets pre_time to millis () when he wants to re-start the timer. Think hard about reply #2. It shouldn't reset millis() to 0 - it should just keep millis() from advancing while it's sleeping. Internally, Time depends upon Arduino's millis() function to keep track to elasped time. Probably while loop on line 140 is done (remoteState >= 20): while (remoteState < 20) {. In the requirements, it says: "Time does not require any special hardware. 2 Answers. val = digitalRead (REED); The digitalRead () function returns an integer value equal to HIGH (1) or LOW (0). That's not time-important so it can just be run next time around. Yes. Expected max RPM is 3750. Then in the loop we’re going to use the Serial. micros () reads the immediate value in TCNT0. I do this on principle every time I use millis() at my Uncles suggestion (he is extremely experienced with Arduino, to a level I have rarely seen. 0 forces the compiler to see 1000 as a float value (you can also use 1000f if you prefer). It executes very quickly and has a good resolution (milliseconds). Keep in mind that the millis () value will overflow afther: 50 days and 70 minutes. The sketch included at the end of this post demonstrates the drift, and. Hi, I am using millis() function to program with something. unsigned long time; void setup () { Serial. More about millis () later. While input pin gets high for more than 10000 milli seconds output pin gets high. Immediately after running the program the first measurement is sent, however, the second (which should be sent after 30 min), is sent only after 1 hour. If you look at the source code for 'delay ()' you will see. Using Arduino Microcontrollers. Experimenting with an ATmega328P on a breadboard. Reading this forum has been game changing for a new arduino user like myself. Nothing else in my code is timer sensitive, so I'd just as soon reset millis() to zero just prior to my need of adding 1000 to it, ever time. Hi i did a little searching and all i could find is: timer0_overflow_count = 0; This does not work in my code i get errors. Example 3: Measuring Button Press Duration. Delta_G July 11, 2023, 5:14pm 5. While it is not a good idea to reset millis, it can be done easily:The demo Several Things at a Time illustrates the use of millis() to manage timing without blocking. The millis feature of the Arduino Code allows the Arduino to display the functions up to the value in milliseconds to 100% accuracy. Using the millis () timer directly, you need to write something like: Serial. We simply need to connect the control pin of the servo to any digital pin of the Arduino board, connect the Ground and the positive wires to the external 5V power supply, and also connect the Arduino ground to the servo ground. The start and end values do not matter, rather it is the difference between them that you are interested in. If my counter goes to 16 and then I press reset through pin 7, I will get 0 6. Example 4: Controlling a Servo with Precise Timing. millis () is incremented (for 16 MHz AVR chips and some others) every 1. Raspberry Pi 40-pin Compatible GPIO. Now I know the millis() resets/rolls over something like every 49 days or something. A couple posters keep pointing users to the Blink Without Delay sketch with Any question. pert May 26, 2019, 7:22am 2. If you instead set previousMillis to: previousMillis = 0 - (interval - 5); Then you will get the behavior you expect I think. e. But you have to handle the interaction between the millis () / micros () related variables. Interrupts can slightly disrupt the timing of code, however, and may be disabled for particularly critical sections of code. In the condition of the second if statement, millis() is 10,000 and lastDebounceTime is also 10,000, so millis() - lastDebounceTime equals zero. CenkayB July 26, 2021, 10:06am 1. You don't have to do anything. your else in that set of if's is causing only a single if to be possible to be true at any one time, and once the now-then line up, only the first one in the line-up will ever execute. the seconds that is what i want to reset. case1: reset timeValue - done by timeValue = millis () set case = case1a. So you could regularly reset m to be equal to the latest reading, even if that reading is lower than m. I'm trying to log data from different sensors, like thermocouples,. so you should check if m > 5000. Ashton March 18, 2013, 1:49pm 1. The return value of millis () function rolls over back to zero after roughly 50 days. i. johnwasser July 15, 2019, 6:53pm #17. So I built a timer that runs off of the millis command, over the course of 4 weeks it gets off by 15 seconds so its A ok in my book (the interval for millis is 997 actually) But so now I'm wondering. Thats fine, i have done all of the above, but i think rollover problem will be still there as in currentTime if the maximum value of millis() arrives and after that instant millis() get reset and starts from zero so in currentTime there will be maximum value of millis() and from subtraction we will get negative number. The Arduino programming language Reference, organized into Functions, Variable and Constant,. millis () is likely to always be greater than zero. Can it be reset to zero and started again within the same sketch? Yes it can, but why would you want to?Then check if more than our waiting time has passed. The return value of millis () function rolls over back to zero after roughly 50 days. reset the count to zero when pin 7 is HIGH. All that happens, on a timer overflow, is that it goes back to zero and starts counting up again. A beginners guide if you need more explanation. g. The maximum time that the counter can accomodate is 2 32 ms. My ISR increments a variable, which lets the rest of my function know what its doing. Yes, just perform a software reset (google resetfunc Arduino) 18,446,744,069,414,584,432 = 0xFFFFFFFF00000070 We can only have 4 bytes, therefore: 0x70 = 112 decimal. If you want to turn it of, regardless of the button state, you can add a boolean flag to your if-statement, to set the timestamp only, when the button was pressed first: In this case you have to reset the button_pressed variable to false, when you are. Right click on the "Arduino Zero Prog. The Arduino has three timers – Timer0, Timer1, and Timer2. Make sure the variable is in the scope of your code by declaring it sometime after wiring. Just like your clock does. 13th May 2016. There is no need to do a reset for the Arduino millis() function’s counter. I'm now tidying up some bits and pieces, and so here is my question: When I select a value to vary (via one of six push buttons and a single rotary encoder) I need to 'hold' the relevant button state. unsigned long myZeroTime = millis (); Hello all, is it possible to reset millis() to zero? because millis() will overflow in about 9 hours, it is better to let it go to zero in a controlled enviroment at a convenient time is stead of in the middle of a calculation. This function returns the number of milliseconds the current sketch has been running since the last reset. Hello, I am working on a project where apart from other functions i have to determine the elapsed time between input state changes, then if it is below a set threshold, enable the outputs. I’ve read online that somebody is trying to reset the hardware timer for. if millis() is near max, and time is less than millis() and (time + timeBetweenReading) rolls, it will repeatly trigger as long as millis() hasn't rolled. This example code prints on the serial port the number of milliseconds passed since the Arduino board started running the code itself. print("Time: "); time = millis(); Serial. Let's clear up some misconceptions: The processor does not reset when the timer overflows. @runciblefish. You need a stamp for every thing x because you'll have to reset each of them to the current millis when the thing gets executed. that will make the carriage stop when the 2nd counter is 0. If the sketch is intended to run for longer than that, It needs to make sure the rollover does not make the sketch fail. e. The RESET button is a white or blue push button located on top of your Arduino board. To use this library, open the Library Manager in the Arduino IDE and install it from there. I am assigning millis() to a long int and then printing the value and it is always 0! I think it has something to do with the library's timer and interrupt. How to capture millisecond in arduino. The normal course of action is to resume right where it left off. First divide by 1000 for the seconds, then by 60 for the minutes then by 60 for the hours then by 24 for the days = ~ 49. At this point you have basically two choices: Research and understand the proper use of millis () to write non-blocking timing code. I verified this behavior with my desktop C++ compiler using the std::is_same struct from. . Then it tells me that an unsigned long (32 bits) ranges from 0 to 4,294,967,295 (2^32 - 1). If the flow stops before 400 milliliters is reached, what is needed to reset the pulse counter to. It doesn’t stop. ‘time’ is relative. Later you compare the different from the current millis() and the value you saved a while ago to see how much time has passed. Zero = Uptime 0 days 00:00:00. The timer does not stop. 3. How can I format millis into a 24 hour display, [HH:MM:SS] that resets every 24 hours, or better yet, insert an authentic. Using millis() to decide when to make the only call to this code in a single "wrap" of millis (a specific 49. Since they're unsigned longs, the maximum value is 2^32 - 1, or 4294967295, so if millis()/micros() is less than the last snapshot taken, the millis()/micros() value has wrapped to zero and we have to subtract the last snapshot. Let say i write an code analogRead. Thank you millis sleep Share Improve this question Follow asked Jun. It allows me to control RGB LED modules. c * As a result, the first "tick" will be be shorter than it should be. See full list on baldengineer. I need the output to stay low for a interval after the sensor goes back to high. Millis () does not back to zero after woke up from deep sleep mode. 024 milliseconds, then. karlcorporal7 October 10, 2020, 10:48pm 1. the DHT temperature sensor may be read once per 2 seconds, if a DHT library remembers the last read in millis it can guard the sensor. case 1:. b=500ms. Pressing it has the same effect as disconnecting and reconnecting the power supply: The board will wait briefly for a new sketch to uploaded, then it will start executing any instructions in the sketch from the beginning. How It Works. When that occurs take the required action (s) and save the value millis () again as the start of the. Number of milliseconds since the program started (unsigned long). If output pin 13 high, then capture how millisecond until the pin 13 goto low. Needed for Leonardo only } //link your buttos here button_blink_the_fog_lights. Serial. Syntax. Arduino Stack Exchange is a question and answer site for developers of open-source hardware and software that is compatible with Arduino. To get the value of the counter at a particular juncture, just call the function – for example: start=millis(); Where start is an unsigned long variable. Loose connection disrupting the processor's power causing it to reset. mondoha May 28, 2020, 9:03pm 1. ESP32 millis not working properly. I have said it breaks libraries and the second approach doesn't alter the contents of millis () in any way. const byte interrupt_Pin = 2; //Sets the pin used for the. Because you set it to 0 on line 137 I guess: loopCounter = 0; //resets loop counter to 0. There are hundreds if not thousands of great tutorials on BWoD in the Arduino context. When the timing resumes you increase startTimestamp by the difference between millis () and. If the sketch is intended to run for longer than that, It needs to make sure the rollover does not make the sketch fail. In the second example, you will cause the roll over with a subtraction of 45. I'd like if we press the first the millis () counter starts. Just like your clock does. Arduino millis() Reset. When you call the millis () function, it returns the current value of the timer/counter in milliseconds (hence the millis () function name). Then, we’ll check the difference between T1 (time zero) and T2 (the current timestamp) and see if it’s equal to or greater than the desired delay time interval (. Instead of trying to reset millis(), we will compare against itself later on. Generally the reason people want to reset it, is that they are. b=250ms after a. Returns the number of milliseconds passed since the Arduino board began running the current program. Is it bad your clock overflows (goes back to zero) at midnight? No it isn't. For accurate timing over short intervals, consider using micros (). what I want to add A2 as A reset button. 024 milliseconds, then incrementing by 2 (rather than 1) every 41 or 42 ticks, to pull it back into synch; thus some millis () values are skipped. odometer April 29, 2012, 11:52pm #14. Data does not start to be being received by PC. Hello, I have a switch which uses a, ESP8266 and relay module connected to it. EllapsedMilliseconds (); Returns the. The actuators do not give feedback, so the program is used to. Perhaps it's named startTimestamp. The actuators do not give feedback, so the program is used to. This code manages to count up the amount of rising edges using an interrupt to increment whenever the input goes up to 5v, however I'm not sure how to reset the count back to zero without causing the output to just be zero. The copy is performed with interrupts disabled in order to avoid a race condition. Then if it sees that the button is not pressed, within your set time, it sets the case back to zero. The . . They do not conflict as millis () strictly reads the immediate value in TCNT0 whereas PWM via timer 0 uses the hardware's ability to compare the value of TCNT0 with the values in OCR0x without affecting the value of any of them. Hi everyone, I am new to Arduino so my question may seem silly . , Case 2 , Case 3 and Case 4) back to accessory mode(i. On each call you get the actual time and the difference to starttime is the time, where the program. millis () is incremented (for 16 MHz AVR chips and some others) every 1. Look for the listing named "Ports (COM & LPT)". To state it another way, the value that is returned by the function millis () is the amount of time that has passed since the Arduino board was powered up. Powering down the board. Some functions will not work while interrupts are disabled, and incoming communication may be ignored. To solve it, write rollover-safe code. The loop reports delta time from the random delay that takes between 100 and 1000 milliseconds. Additionally, we have added reset function too. George. com If you still want to reset millis, you can use the following: extern volatile unsigned long timer0_millis; unsigned long new_value = 0; void setup(){ //Setup stuff } void loop(){ //Do stuff //-------- //Change Millis setMillis(new_value); } void setMillis(unsigned long new_millis){ uint8_t oldSREG = SREG; cli(); timer0_millis = new_millis; SREG. It starts at zero milliseconds each time the board is reset, and is incremented each millisecond by a CPU hardware counter. Short-circuit causing the processor to overheat then reset. About this insistence that the millisecond timer be reset: expect the Arduino to react about as violently as I would react if you grabbed my wrist and tried setting the time on my watch. And rest follows like reset the timer, pause counting, etc. You can use millis () to determine how long it has been since some previous event: unsigned long currMillis =. Preference and clarity might dictate you avoid using "lastMillis" or "previousMillis" as it's not the last millis () when you set it, but it becomes that, so your English teacher might suggest using "timeStamp" or "processGood" or something that means the same thing everywhere you use the term. If the difference is equal to or greater than 1000 then the button has been pressed for 1 second. I have written a simple code to read and write data via USB on Arduino Console from/to Arduino Zero (powered by external battery). It is possible to serial print how milliseconds every output high. We can display up to 4 digits after the decimal. The main working of the firmware is based on millis() function and BOUNCE 2 library functions. There is other stuff that is run if millis since last run is more than 100, like a LED pulse. Make previousMicros a static variable so it doesn't get reinitialized to 0 every time, then your code will work. A few ways, depending on your level of comfort: You can declare the stock Arduino Timer0 OVF "weak" and write your own where you can insert your ISR. Programming Questions. elapsedTime = currentTime - previousTime.