Questions tagged [isr]

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

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49 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?
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3answers
727 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 ...
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1answer
34 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) { ...
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23 views

ISR definition causing boot loop?

I am trying to compile and upload code to an Arduino Uno from the command-line, however I seem to be experiencing an odd issue. When I compile this code: #include <avr/interrupt.h> #include &...
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52 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 ...
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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, ...
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97 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 ...
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1answer
55 views

Does this sound like a good approach to decoding a dumb keypad?

The background: I bought a "dumb" 8-pin 4x4 keypad for use in a project. (This one: https://www.sparkfun.com/products/14881 It has a wire connected to each row, and a wire connected to each column. ...
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Arduino SPI ISR

Is there any way to trigger a ISR after a SPI transfer is complete? I am trying to send messages from one of three LORA radios and have the other two read the message. I am using the Radiohead (RF95) ...
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137 views

ESP32 changing PWM duty in ISR

I'm implementing code for a multiplexed 7-segment display (4 letters), e.g. it has two common cathodes and each pin corresponds to two segments depending on which cathode is grounded. I have written ...
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2answers
133 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 ...
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1answer
106 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() ...
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1answer
85 views

attiny85: ISR not triggering for PCINT2?

I am using an attiny85 to read the fan speed reported by a pair of 4-wire fans. I had planned to attach the TACH output from the fans to pins 1 and 2, but I ran into a problem: I was able to handle ...
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2answers
444 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? ...
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1answer
138 views

Arduino ISR timing question

Im trying to understand how the Arduino ISR keeps track of timing between pulses stored in a variable, if that variable is latter used. Say, for example, you have a magnet mounted on a circular ...
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309 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 ...
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1answer
31 views

Is it possible to HTTP inside an ISR

I am developing a 247 monitoring system with Arduino. The values need to be sent to server periodically as well as upon interrupt (Watchdog). To access the internet, I am using the SIM800 module. Now, ...
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1answer
2k views

Soft debouncing from an interrupt during stand-by

My current setup has the arduino in 'stand-by' power saving mode, therefore i am unable to use any means of a traditional soft debouncer, such as Bounce2, as far as I know. I went ahead and attached ...
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2answers
3k 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 ...
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1answer
3k views

Problem on multiple interrupts operation on Arduino Uno

I experimenting with the interrupt ISR using Arduino Uno. In my circuit, I am taking two switches which are connected with Uno's interrupt pins, pins 2 and 3, and also taking multiple LEDs which are ...
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1answer
78 views

Can't operate relay's functionality in ISR function - SOLVED

In recent project, I have to operate my relay based on falling edge of Square wave. Here, falling edge detect by using interrupt. So, whenever Arduino detect falling edge using interrupt, ISR function ...
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2answers
485 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 ...
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1answer
400 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 ...
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1answer
462 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). ...
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1answer
111 views

Software PWM implementation on ATTiny44 screws up timing functions

I've came up with a poor man's implementation of software-based PWM for the ATTINY44 and I'm kinda stuck now. It works but it screws up the timing functions badly (delay, delayMicroseconds) no matter ...
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3answers
682 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 ...
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2answers
941 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 ...
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3k 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 ...
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3answers
182 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(); } ...
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66 views

Do ISRs have to be defined in top level Arduino program?

I'm currently attempting to implement some interrupts on an Arduino project. Looking through some of the examples, it appears that all the ISRs are defined in the top level Arduino program. I'm ...
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4answers
8k 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 ...
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1answer
137 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/...
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3answers
3k 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 ...
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262 views

ISR halts in DUE

I am using the following simple code to test the interrupt functionality of due: void aMillion(){ for(int i = 0; i < 1000000; i++){ if(i % 1000 == 0){ Serial.print("m"); ...
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1answer
150 views

Engine Speed Control Observation

I am using an Arduino Mega to control the speed of an internal combustion engine. The speed is sensed via a Variable Reluctance Sensor (VRS) on the crankshaft. This signal is then converted into a 5V ...
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1answer
400 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 ...
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2answers
1k 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 ...
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62 views

Interrupt numbering

I'm using an Arduino Mega and four of its interrupts. Each interrupt is only used to start/stop a timer, depending if it's rising or falling, so effectively runs the same function. Does anyone know if ...
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3answers
2k 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 ...
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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 ...
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0answers
622 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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2answers
377 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 ...
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1answer
106 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 ...
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2answers
10k 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 ...
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1answer
404 views

Arduino Due interrupt is taken but not executed completely

I tried to build a simple l-meter with my arduino due. I programmed a simple frequency meter with one timer and one counter. The timer takes an interrupt each 10s, 100ms, 10ms and 1ms. But ones the ...
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1answer
1k views

Hardware Interrupt Triggered Randomly

So there is this pretty generic part of my project that involves triggering an ISR that will flip a boolean value. I have set up the software side like so: void setup() { attachInterrupt(...
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1answer
371 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 (...
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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 ...
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2answers
547 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()?
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1answer
478 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 ...