{"id":9683,"date":"2023-05-18T15:40:35","date_gmt":"2023-05-18T13:40:35","guid":{"rendered":"https:\/\/deepbluembedded.com\/?p=9683"},"modified":"2023-08-17T23:49:57","modified_gmt":"2023-08-17T20:49:57","slug":"arduino-software-interrupts","status":"publish","type":"post","link":"https:\/\/deepbluembedded.com\/arduino-software-interrupts\/","title":{"rendered":"Arduino Software Interrupts"},"content":{"rendered":"\n
In this tutorial, we’ll discuss Arduino Software Interrupts<\/strong> and how to generate a software interrupt (trap) in Arduino. We’ll implement an Arduino Software Interrupt Example<\/strong> project to test what we’ll learn throughout this tutorial. Without further ado, let’s get right into it!<\/p>\n\n\n Software interrupts<\/strong> are interrupt signals that can be fired with specific software instructions. Some microcontrollers support native software interrupt instructions while others don’t have dedicated assembly instructions for the CPU to get an interrupt from the software.<\/p>\n\n\n\n Other techniques can be implemented to programmatically enforce an interrupt to the CPU within your software even if it doesn’t have a soft interrupt instruction. This of course requires some workarounds but it’s not that hard to do in general.<\/p>\n\n\n\n A software interrupt can be referred to as a Trap as well. Which is a technique to signal the CPU within the software to change the mode, throw an error, indicate an arithmetic error, or signal the OS.<\/p>\n\n\n\n It’s stated clearly in the Arduino UNO’s Atmega328p datasheet that it doesn’t have a dedicated assembly instruction to trigger a software-generated interrupt signal. But as we’ve stated earlier, we can still implement some workarounds to fire software-generated interrupt signals.<\/p>\n\n\n\n One technique to generate a software interrupt is clearly stated in the datasheet itself. Which is to enable any external interrupt pin (IRQ) and set it as an output pin. Writing to any pin of these will trigger an interrupt, and that’s how we get a software-generated interrupt even if it’s not supported by the microcontroller.<\/p>\n\n\n Arduino’s Atemga328p microcontroller doesn’t have a dedicated assembly instruction that generates a software interrupt. Instead, a hardware interrupt like external IRQ pins (e.g. INT0) can be written to by software to trigger an interrupt, which is also considered as a software-generated interrupt.<\/p>\n\n<\/div><\/div>\n\n\n In this example project, we’ll test Arduino Software Interrupts. And here is how we’re going to do it.<\/p>\n\n\n\n First of all, we’ll use the INT0 (IO pin2) as an interrupt signal source but will trigger it from the software and will set it as an output pin. It’s not going to be connected to the push button or anything.<\/p>\n\n\n\n The push button input, however, is going to be connected to an IO pin8 that we’ll set as an input pin. Whenever the push button is pressed we’ll debounce it, once a click is confirmed, we’ll send a pulse (LOW->HIGH, RISING) to the output pin (INT0) which is going to trigger an interrupt event.<\/p>\n\n\n\n In the ISR handler for INT0 interrupt, we’ll toggle an output LED. I know, it’s not very intuitive but it’s still a valid test to verify the concept and make sure everything behaves as expected.<\/p>\n\n\n Here is the wiring diagram for this example showing how to connect the LED output, and the push button to the input pin (pin8). And note that the INT0 (pin2) is set as an output pin and left unconnected.<\/p>\n\n\n\nTable of Contents<\/h2>\n
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\n\n\nSoftware Interrupts<\/strong><\/h2>\n\n\n
\n\n\nArduino Software Interrupts<\/strong><\/h2>\n\n\n
\n\n\nArduino Software Interrupt Example<\/strong><\/h2>\n\n\n
Wiring<\/h4>\n\n\n