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Questions tagged [isr]

Interrupt Service Routine. A function which gets called in response to an interrupt signal.

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22 votes
3 answers
6k views

Can a function be called automatically when an input changes?

Currently, my sketch is checking an input pin every time round the main loop. If it detects a change, it calls a custom function to respond to it. Here's the code (trimmed down to the essentials): ...
Peter Bloomfield's user avatar
11 votes
2 answers
1k views

Are function pointer assignments atomic in Arduino?

The following snippets are from TimerOne library source code: // TimerOne.h: void (*isrCallback)(); // TimerOne.cpp: ISR(TIMER1_OVF_vect) // interrupt service routine that wraps a user defined ...
Joonas Pulakka's user avatar
9 votes
2 answers
7k views

Arduino interruption (on pin change)

I use the interrupt function to fill an array with values received from digitalRead(). void setup() { Serial.begin(115200); attachInterrupt(0, test_func, CHANGE); } void test_func() { if (...
user277820's user avatar
9 votes
1 answer
6k views

Is volatile needed when variable is accessed from > 1 ISRs, but not shared outside ISRs?

It's clearly documented that when global data is shared with an ISR and the main program, the data needs to be declared volatile in order to guarantee memory visibility (and that only suffices for 1-...
Joonas Pulakka's user avatar
9 votes
2 answers
4k views

How to update a variable in an ISR using Timers

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value ...
UserK's user avatar
  • 559
8 votes
2 answers
20k views

Why the need to use the volatile keyword on global variables when handling interrupts in Arduino?

I am familiar with the keyword Volatile being used to declare variables that are shared among multiple threads on a software application (basically on a multithreaded application). But why do I need ...
user avatar
5 votes
4 answers
7k views

Is `millis()` affected by long ISRs?

I have a project that uses timers and interrupts frequently. A lot of CPU time is spent handling ISRs over an extended period of time. Would this affect code inside the main loop that relies on the ...
Anonymous Penguin's user avatar
4 votes
2 answers
607 views

How to get around passing a variable into an ISR

Okay so you aren't able to pass a variable into in ISR. This is causing problems for me. I'm using a rotary encoder, and I need it to be connected to an interrupt pin and running a ISR. When using ...
AJ_Smoothie's user avatar
4 votes
2 answers
863 views

Interrupts: use of the "volatile" keyword with a structure pointer for button debounce

I've written a small sketch targeted at the Arduino Uno (ATmega328P) to debounce a mechanical pushbutton using the summing/integration technique: #include <IntegratingDebounce.h> #define ...
w_hile's user avatar
  • 143
4 votes
1 answer
344 views

Why does timer ISR not execute?

This is my code which I have written as a library #include "avr/interrupt.h" #include "Arduino.h" #include "AllTimer.h" AllTimer::AllTimer() {} void AllTimer::dofun(void) { //TIFR1 |= _BV(...
explorer's user avatar
  • 379
4 votes
1 answer
635 views

ISR for very fast processes, strange code found. Has ISR effect on timer behaviour?

I found the following code within an example for performing very fast changes on a PWM-output. It works, however I'm wondering about some details. TIMER2 was set up in setup() as follows: TCCR2A = 0; ...
Ariser's user avatar
  • 577
4 votes
3 answers
262 views

why does function affect my ISR?

I am currently running this piece of code: main.ino #include "speed_profile.h" void setup() { // put your setup code here, to run once: output_pin_setup(); cli(); timer1_setup(); sei(); } ...
Lamda's user avatar
  • 141
4 votes
1 answer
156 views

Interrupts Within Critical Statements

I've redone a previous Arduino sketch I posted in which I was having trouble capturing encoder counts within critical statements, having no luck properly attaching and detaching interrupts. I've ...
wickedhurricane's user avatar
3 votes
3 answers
3k views

What is the right way to query an I2C device from an interrupt service routine?

The ADXL345, for example, requires that interrupts are responded to by querying the INT_SOURCE (interrupt source) register. In example code for the SparkFun ADXL345 Arduino Library, there is code that ...
James Brusey's user avatar
3 votes
1 answer
91 views

Why no brackets after Interrupt routine inside attachInterrupt

I'm just curious as to why there are no brackets at the end of the ISR when attaching and assigning the interrupt command? attachInterrupt(digitalPinToInterrupt(interruptPin), blink, CHANGE); ... ...
Diesel's user avatar
  • 144
3 votes
1 answer
2k views

Arduino Uno R3 ISR does not work on pin 2?

I have an Arduino Uno R3. I have a paddlewheel waterspeed sensor that I use on an ISR on pin 2. The power supply is approximately 8v stepped down to 4.92v with a circuit yanked from the phone charger. ...
ADDP's user avatar
  • 31
3 votes
3 answers
4k views

Breaking a switch case from an ISR

I'm struggling with something. My CPU sits in a switch case state machine like this: switch(expression) { case constant-expression_1 : statement(s); break; /* optional */ case ...
makepeace's user avatar
2 votes
6 answers
8k views

Is possible to set a pin faster than digitalWrite?

I am currently using arduino library to logically set my digital pins high or low, but I just realized how slowly it actually sets those pins, which is especially problem as i am doing this in a ISR ...
Carlton Banks's user avatar
2 votes
2 answers
560 views

Using interrupts as flags/latches without any ISR

I've got an Arduino Mega periodically running an (~400ms) operation that is sensitive to repeatable timing, so I don't ever want it to be interrupted. But, I'd like to be able to use an interrupt ...
Nicholas's user avatar
  • 123
2 votes
3 answers
3k views

Arduino delay inside of an Interrupt

Using the delay function inside of an ISR is frowned upon when programming in an Arduino. The general response to solve this desire is to design the program to delay in a more cleanly way outside of ...
Liro's user avatar
  • 23
2 votes
3 answers
5k views

What is the maximum length an Interrupt Service Routine?

In general, what's the maximum length of instructions that can be included in an Interrupt Service Routine? The docs say an ISR should be "as short and fast as possible", but that's bit vague. For ...
Cerin's user avatar
  • 1,628
2 votes
2 answers
6k views

ATmega328p hangs on USART RX interrupt

I was able to use USART without interrupt driven and it worked perfectly! However, when I tried adding interrupt on USART_RX_vect, the program does not work as expected anymore. Below is my small ...
COMP's user avatar
  • 137
2 votes
2 answers
146 views

Why impedance between I/O pin and ground drops when Arduino is not powered

I have a 4KHz 5V pulsed signal connected to Arduino UNO pin2 (ISR). When the board is powered, the pulse is attached to ISR rising edge, and is working as intended. I don't know the output impedance ...
7E10FC9A's user avatar
  • 209
2 votes
1 answer
2k views

AttachInterrupt - fail to initiate inside a class [duplicate]

I'm trying to create a class that uses attachInterrupt, but get this error msg: In member function 'void ledDoor::attach()': ClosetLedStrip:31:82: error: invalid use of non-static member function ...
guyd's user avatar
  • 1,049
2 votes
4 answers
464 views

Atmega168 breaking out of ISR

I wrote a code to handle an ISR triggered by UART input. I'm looking for 2 characters or more. I can handle extra characters and garbage values, but problem arises when I get less than 2 chars, ...
tsf144's user avatar
  • 243
2 votes
1 answer
209 views

Mildly accurate oscilloscope using Arduino Uno R3

I'm trying to make a mildly accurate oscilloscope using Arduino Uno R3 and I've done some research on the best method to do so. First of all I need to measure the voltage with a rather high sampling ...
infinite's user avatar
2 votes
1 answer
1k views

Arduino IDE with ATtiny85 error "multiple definition of `__vector_5"

I am having a problem compiling the code for my ATtiny85 circuit. I am using the timer/counter0 in normal mode so that when it overflows it triggers the TIMER0_OVF_vect ISR. When I have that ISR in ...
Eric Navarrete's user avatar
2 votes
1 answer
590 views

How to user timer interrupts for times longer than can TNCTx can keep track of?

I am trying to program my Arduino Mega 2560 to effectively create a PWM signal on any digital pin using timer interrupts and timer1. The pins will pulse a finite amount of times (not indefinitely). I ...
Sebastian Freeman's user avatar
2 votes
1 answer
1k views

Irregularly triggering an ISR using timers

I seek to call an ISR routine after a fixed time of 400us. This action needs to be done every now and then (in the range of 0.8-3.0ms). For that matter, I thought I'd set timer2 to CTC mode, use OCR2A ...
mike's user avatar
  • 347
2 votes
1 answer
120 views

Is ESP8266 dropping an interrupt?

I want to use interrupts on my ESP 8266 to monitor the digital outputs of a power meter and water meter. The idea is to increment a counter in the ISRs and at some point to take the value of the ...
Plamen Peev's user avatar
2 votes
1 answer
347 views

ATtiny85 giving multiple wake from IDLE if INT0 held low

Desired behaviour: Go to IDLE sleep mode. When PB2 (blue trace) goes low wake up and give a 10 ms HIGH on PB1 pulling a pull-up low (yellow trace on Figure 1). Go to 1. What I get: Figure 1. (1) ...
Transistor's user avatar
2 votes
1 answer
160 views

Hardware interrupt calling two ISRs

I've spent three days on this, and either I'm blind to something, or something just ain't right. Doorbell. Front door switch and back door switch. Two interrupt service routines, one attached to each ...
Baxter Tidwell's user avatar
2 votes
2 answers
2k views

How do I use interrupt service routines inside libraries and classes?

I'm trying to have a millis() timer run to emulate a hardware timer inside a library, but I'm having issues compiling the code. I want the callback (pseudo ISR) to be part of the class, and not use ...
waspinator's user avatar
2 votes
2 answers
512 views

ISR executes twice if data coming through SoftwareSerial

I am using Arduino Pro Mini to get GPS info from a u-blox NEO-M8N chip and display it on a Adafruit OLED display. NEO-M8N has a PPS(pulse per second) output which is aligned to GPS's second. Because ...
HL. Chen's user avatar
2 votes
0 answers
1k views

Does Proteus simulate external interrupts properly using Arduino? I can't get them to work

I am trying to simulate an interrupt with an Arduino Uno in Proteus. This is the simple test code that I'm using: void introutine() { digitalWrite(13,HIGH); } void setup() { pinMode(13,OUTPUT); ...
user avatar
1 vote
4 answers
192 views

Is there anything wrong with this code

Hi I'm pretty new to cpp. Could someone review my code and explain any pitfalls or problems? Below is the code and an example to read from a flow meter with a hall sensor. Thanks in advance. Greg /...
Yardie's user avatar
  • 23
1 vote
2 answers
851 views

ISR and multiplexing- time required to execute the code in Arduino

Below is an Arduino sketch for a basic animation, taken from the book Beginning Arduino by Michael McRoberts. Also, the connections have been shown. From what I have read elsewhere, this is the ...
stochastic13's user avatar
1 vote
1 answer
81 views

How do I properly use an ISR inside a class definition?

I want to write a class for a model bike. For controlling the steering I use a DC motor with two encoders. To get the steering angle stAng of the bike, I attach a interrupt to the pin ST_ENC_A where ...
Ole's user avatar
  • 13
1 vote
1 answer
205 views

How do I temporarily disable TIMER5 Interrupts?

I have a fairly complex autonomous robot program that is getting into trouble when executing controlled turns. I constructed a very small program to test just the turns, and this works fine. When I ...
starship15's user avatar
1 vote
1 answer
168 views

Arduino Timer0 Piggyback

As described here https://learn.adafruit.com/multi-tasking-the-arduino-part-2/timers I use timer 0 to get my own timer with a milliseconds resolution. It is setup like this: void setup (void) { ...
Sören's user avatar
  • 41
1 vote
3 answers
2k views

ISR executes even though an interrupt is not triggered

I am trying to implement a function queue scheduling system. INT1 is connected to a button and int1task causes an LED to flash. typedef void (*funcptr)(void); TPrioQueue *queue = NULL; void int1ISR()...
sharon's user avatar
  • 21
1 vote
2 answers
2k views

How to exit out of a timer interrupt (ISR(TIMER1_COMPA_vect))

I have a code here where I collect an array of data and do some data analysis with the data. The only thing I'm struggle with is how to exit the ISR after I am done running my code. I am using a pre-...
Dema Govalla's user avatar
1 vote
1 answer
2k views

What is the call to cli(); routine in interrupt service routine for SPI?

I see this in examples of ISR code but what is it?
Martin's user avatar
  • 11
1 vote
1 answer
967 views

Volatile variable not updating from timer ISR

I know this is a problem that has come up many times but I can't seem to get this code fragment to update the count variable on an ATMEGA328P. I am using an Arduino Uno as a development board, with ...
user avatar
1 vote
3 answers
1k views

Custom ISR triggering function/value

Is there a way to write a custom function which would be the mode/reason to trigger an interrupt. I have an analog joystick connected to my arduino analog pin. It reads a value of 689 on one end and 0 ...
Vignesh's user avatar
  • 25
1 vote
1 answer
834 views

UNO Timer 1 CTC mode not resetting TCNT1

I'm trying to set up timer 1 to run an isr in CTC mode. no matter what i set OCR1A to it always executes at the same frequency and if i print out TCNT1 I get values higher than OCR1A. here is my Code ...
thermite's user avatar
  • 111
1 vote
1 answer
686 views

Correct usage of SPI with ISR

My Arduino needs to do: Run ISR as many times as possible/ as fast as possible. Occasionally receive data over I2C. Output data over SPI in ISR. My question is regarding SPI and ISR. The ...
aWiseMan's user avatar
1 vote
1 answer
64 views

How to properly send bytes between RPI and Arduino over I2C while using ISR without IOerrors?

I have a I2C connection between an RPI 3B+ and Arduino Nano. I want to send a key and a corresponding value byte, and the arduino does something with that inside a timed ISR. Which works. But I get ...
aWiseMan's user avatar
1 vote
2 answers
199 views

Timer Interrupt Collision

I am working with a MEGA2560 trying to implement velocity ramps for three steppers at the same time. The goal is to move to different positions applying accelerations and decelerations while finishing ...
Izar Thomson's user avatar
1 vote
2 answers
1k views

ISR vs state change detection on button

Hi I was wondering if a digitalRead state change detection could be saved in a variable like counter++, just like you can do with an interrupt function. arent these two operations almost the same? ...
Jim's user avatar
  • 31