TinyRTOS: Real-Time Operating System in C

TLDR

• Designed, programmed, and tested a custom real-time operating system (RTOS) kernel in C on an Intel DE1-SoC FPGA board with a team of four.
• Implemented dynamic memory using first-fit allocation with a linked-list free list, block splitting/coalescing, fragmentation tracking, and leak tests.
• Built dynamic task management with a preemptive, priority-based scheduler. Two-level design: a red-black tree stores active priorities, each pointing to a FIFO ready queue for tasks at that priority (O(1) highest-priority pick, O(log n) updates).
• Added mailbox-based inter-process communication (IPC) with a ring buffer for typed messages and sender IDs, supporting inter-task messaging and I/O.
• Included a Keyboard Command Dispatcher (KCD) system task to parse keyboard input and route commands to registered tasks.

Architecture

• Data structures: Task Control Blocks (TCBs), red-black tree of active priorities, per-priority ready lists, linked-list free list, mailbox ring buffer.
• Scheduling: preemptive priority scheduling; pick via RB-tree minimum then pop from the corresponding ready queue; supports yield and priority changes.
• Memory: first-fit allocation, 8-byte alignment, header guards with task ID, adjacent coalescing, external fragmentation counter.
• IPC & I/O: mailbox create/send/recv with wrap-around copy; KCD routes “%x…” commands as messages to tasks.

Code

What I Learned