Quatros

Abstract

Hands-on experience is crucial to truly understanding the principles of operating systems (OS). This paper describes a preemptive, multithreaded embedded OS assigned as a project in a junior-level OS course. It targets the popular 8051 instruction set architecture (ISA) and can run with as little as 128 bytes of RAM and 1 KB of program memory with preemption and synchronization primitives such as semaphores. It is written in C and assembly and compiled using the open-source Small Device C Compiler (SDCC). It runs on the free EdSim51 simulator, which simulates common peripherals such as LCD, keypads, 7-segment LEDs, ADC, and UART all in high fidelity. This course project has received positive feedback from students who took the course.