Preemptive Multitasking on Atmel AVR Microcontroller

摘要

This paper demonstrates the need for multitasking and scenario where multitasking is the only solution and how it can be achieved on an 8-bit AVR microcontroller. This project explains how to create a simple kernel in a single C file, and execute any number of tasks in a multithreaded fashion. It first explains how the AVR engine works and how it switches between different tasks using preemptive scheduling algorithm with the flexibility of blocking a task to allowing it more execution time based on their priority level. The code written for this project is basically in C, however the kernel code is mostly assembly functions called by C. The development environment is Atmel Studio. The code is in such a way that it can be ported over any 8-bit AVR microcontroller, however, this project demonstrates the results in both simulation and hardware chip on device Atmega8A.