Questions tagged [isr]

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

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21
votes
3answers
5k 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): ...
11
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2answers
967 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 ...
9
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1answer
5k 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-...
8
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2answers
4k 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 ...
8
votes
2answers
3k 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 ...
7
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2answers
14k 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 ...
5
votes
3answers
6k 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 ...
4
votes
2answers
446 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 ...
4
votes
1answer
325 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(...
4
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3answers
210 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(); } ...
3
votes
3answers
1k 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 ...
3
votes
1answer
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. ...
3
votes
3answers
3k 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 ...
2
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6answers
6k 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 ...
2
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2answers
5k 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 ...
2
votes
3answers
4k 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 ...
2
votes
4answers
408 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, ...
2
votes
2answers
53 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 ...
2
votes
1answer
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 ...
2
votes
1answer
495 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 ...
2
votes
2answers
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 ...
2
votes
2answers
460 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 ...
2
votes
1answer
90 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 ...
2
votes
0answers
937 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); ...
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3answers
531 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 ...
1
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3answers
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()...
1
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1answer
362 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?
1
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1answer
77 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) { ...
1
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1answer
476 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 ...
1
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1answer
667 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 ...
1
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3answers
945 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 ...
1
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1answer
598 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 ...
1
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2answers
729 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? ...
1
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1answer
584 views

Arduino (weird) ADC problem

I'm trying to read to voltage output of module ACS712. Here is my problem: The module outputs a voltage around 2.5V, however, arduino sends the value "1023" to the PC. (Gives a reading of 5V). ...
1
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1answer
204 views

Having trouble using RTC if I set an ISR for a 1 second timer

I built a sketch using some timer ISR code to get a trigger every second. (for the Atmega328 chip I use the following code I got form the internets. It works) It runs fine and I get a trigger/...
1
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1answer
130 views

Using AVR Timer Within an ISR

I'm trying to create an ISR which operates for 15 seconds when a particular button is pressed. I'm attempting to use the AVR functions on my Arduino Uno to start counting when it enters the ISR, then ...
1
vote
1answer
514 views

Timer (or other) interrupt happens while servicing an interrupt - how to accurately handle the second one?

This seems like a simple question but I'm not finding an answer so far: at a high level, say I have a timer interrupt and some input interrupt. The input arrives, the ISR is entered, interrupts are (...
1
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2answers
661 views

Is it correct to use pulseIn() in ISRs?

Since it is not right to use millis() in an ISR to calculate duration of the input, Is it correct to use pulseIn()?
1
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0answers
51 views

One ISR should be called, but both ISR has been called on Arduino UNO

I experimenting with the interrupt ISR using Arduino Uno. In my circuit, I am taking two mechanical switches that are connected with Uno's interrupt pins, pins 2 and 3, and also taking a built-in LED ...
1
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0answers
43 views

can an ISR change the value passed by pointer while the subroutine is executing?

So I am working on a project where the board plays a song on a buzzer using PWM and I want the song to stop when i press an external button typedef enum stateType_enum{ waitPress, debouncePress, ...
1
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2answers
2k views

How time intensive or how long can an ISR be?

I would like to code my ISR to be time intensive or interrupt the main program for atleast 1 or more seconds. My goal is to verify that if I am reading a sensor in the main loop, would it stop reading ...
1
vote
1answer
113 views

Making a composite waveform using a single TIMER interrupt

I'm writing software for a laser tag gun, which under the system we use needs the output waveform to be a carrier wave of 57600Hz with a signal wave of 1800HZ for about 50ms Using the Tone library (...
1
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0answers
2k views

attiny85 in sleep mode failing to wake properly [closed]

For my attiny85, I'm having trouble getting it to sleep and wake up cleanly. I have a sleep mode with a watchdog timer that wakes every 8 seconds, or when interrupted. And then when that has repeated ...
0
votes
4answers
11k views

How to set up one second interrupt/ISR for ds3231 RTC

I am able to set up one hz interrupts using millis and other timers, but would like to do it instead using the RTC I have attached (DS3231) I am not sure how I can do that. Can someone point me to a ...
0
votes
2answers
459 views

Difference between ISR and other functions in AVR twi library

I was studying the ISR for twi and I want to know how is it working. I have two questions about the code handling for ISR and the other functions and what they do exactly: My first question is about ...
0
votes
1answer
44 views

Arduino using delay in I2C receiveEvent

I have read before that you can't use delay() inside I2C receiveEvent because it is an ISR. What I want to do is as follows: I have a servo connected to my Arduino Uno and I want to control that using ...
0
votes
2answers
339 views

Serial Interrupt

I want to create a simple program, that responds to me sending a character over the Arduino IDE console. I am using an arduino UNO. Here is my program: volatile bool MeasReceived=false; ISR(...
0
votes
1answer
199 views

How to stop sending the last received char of UART echo function?

I developed a code for uart based ISR with linear buffers, the problem is that it keep sending the last received char in Arduino IDE. Here's the application code: #include "uart_new.h" void setup() ...
0
votes
2answers
675 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 ...
0
votes
1answer
2k views

Usage of SPI inside an ISR

I learned, that SPI-code uses interrupts. So is it true then, that I can't use SPI related code inside an ISR? Background: I want to capture one or more revolution speeds with an MCP23S17. I rewired ...