Month: December 2010

Implementing AVR interrupts

Before we go to the code part, let’s what is needed to run interrupts successfully. These conditions apply to all AVR interrupts. First of all, we need to enable global interrupts by setting global Interrupts enable bit (I) in the SREG register. This is crucial as this bit enables or disables all interrupts in the AVR microcontroller. So each time you are setting up an interrupt, be sure this bit is enabled. The next thing is enabling individual interrupt bits on a particular peripheral control register. Without setting this bit – wanted interrupt won’t work either. And the last thing is to be sure that there are required conditions for an interruption to occur. For instance, if you set timer overflow interrupt, be sure this overflow will occur. Defining AVR interrupts Now we can get to some code as the practice is the best teacher. If you look at various C compilers, you’ll find that interrupt defining syntax may differ across them. This is mainly because compilers stay away from hardware-specific details, so it is up to the software developer…

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Basic understanding of microcontroller interrupts

This tutorial is based on Atmega328 microcontroller, which is popular in Arduino boards. So you’ll be able to test all code examples on Arduino as it can serve as general purpose AVR test board with no problem. Understanding Interrupts Probably you won’t be able to find a microcontroller without interrupt capability. These are essential attributes of any modern microcontroller or processor. They may seem confusing and tricky at first glance, but during the time, you will find out that regular MCU operation is impossible without interrupts. Interrupts can be compared to real-life events. Look around – all your activities are full of them. For instance, you are reading this tutorial and find it interesting, so you are all in it. But suddenly, your cell phone rings. What do you do? You remember the last stroke you’ve read and answered the phone. One phone conversation is over; you return to your reading as if nothing happened. Well, this is only one example of interrupt to give some visual clue what interrupts are.

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