RTOS for ARM7

The paper presents a new preemptive real-time operating system for the ARM7 core. The source code for the LPC213x processors with the ARM7TDMI-S core is available [1]. The required mechanisms, such as process handling, dynamicmemory management and binary semaphores, are implemented both in a simple and modular manner. The developed scheduling algorithm is priority-based to ensure hard real-time scheduling of the highest-priority process. Deadlock situations are pointed out. The first-fit dynamic-memory management algorithm is used. The memory allocations are organized in an ordered linked list. To invoke the scheduler timer0, an interrupt request is used, while the system calls are performed by the software interrupt exceptions. The non-system exceptions are caught and can be handled by or without the system. The system properties are measured on the LPC2138 processor.