How do I write ISR-safe code (interrupt service routines)?

Writing ISR-safe code is crucial to ensure that your system functions correctly when handling interrupts. Here are some key points to keep in mind when developing interrupt service routines in C++:

  • Avoid using non-reentrant functions: Functions like malloc, printf, etc., can cause issues if called in an ISR, as they may not be thread-safe.
  • Keep the ISR short: Minimize code execution time in an ISR to avoid delaying other interrupts.
  • Use volatile variables: Variables shared between ISRs and main code should be declared as 'volatile' to prevent compiler optimizations.
  • Avoid blocking calls: Don't use functions that may block, such as sleep or wait, as they could lead to missed interrupts.

Here's a simple example of how to write ISR-safe code:

#include <iostream> volatile bool dataReady = false; void ISR() { // Signal that new data is ready dataReady = true; } int main() { // Simulate enabling interrupts and calling the ISR ISR(); if(dataReady) { std::cout << "Data is ready to be processed!" << std::endl; dataReady = false; // Reset the flag } return 0; }

ISR Interrupt Service Routine C++ programming ISR safety volatile variables

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