A real time operating system for PIC microcontrollers

Embedded systems are widely used for many applications like mobile phones, mp3 players, image processing, communication systems, biomedical applications and industrial control systems. As they are designed for specific tasks, embedded systems' sizes are quite small. Because of their small sizes, microcontrollers are very suitable for embedded systems. Despite having hardware constraints, embedded systems have software that commonly operate in real-time. Embedded systems have different requirements compared to traditional software systems, such as, limited resources, variable application reqiurements and real time constraints, traditional software systems do not fit their requirements. In addition, classical operating systems do not ensure usage criteria as well. Therefore, in order to achieve these goals, designing a real time operating system for embedded systems is the purpose of this project. Due to their popularity, economic prices, easiness to get and use, strong support by the vendor, basic reset and clock circuits, PIC microcontrollers are chosen as the hardware platform of this project. With MPLAB integrated development environment, ANSI C compatible MPLAB C18 compiler is used for developing the project. PIC Operating System (PICOS) is intended to be used for embedded systems and compatible with PIC 18FXXX, PIC24XXX and PIC32XXX families. Typical PIC applications in industry are based on cooperative scheduling. PICOS supports preemptive scheduling as well as cooperative scheduling. It is quite small, basic and easy to use. It has very little RAM, ROM and CPU usage. Kernel structure is also very basic as well.