About lttit

A dynamically programmable distributed real-time operating system

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skaiui2

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README.md

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LTTit

中文介绍

LTTit is a distributed embedded operating system that enables runtime migration of compiled programs across heterogeneous bare‑metal microcontrollers. The system unifies multiple MCUs into a single execution environment where computation can move between nodes without restarting.

Demo Video

Full demonstration:

https://github.com/skaiui2/lttit/raw/main/video/migrate.mp4

Demonstration Summary

The demo shows the complete workflow of migrating a running program between two MCUs:

Writing a program in ccBPF, a small C‑subset language
Compiling the program directly on the MCU into bytecode
Executing the bytecode inside a lightweight virtual machine
Capturing execution state at runtime
Transferring the state across heterogeneous nodes
Resuming execution on the target MCU without restarting the program

Core Concept

LTTit uses ccBPF, a compact language and VM designed for constrained devices. It provides:

On‑device compilation
Virtual machine execution
Instruction‑level state capture
Built‑in migration primitives

Migration is part of the execution model itself, not an external mechanism.

System Components

LTTit consists of the following subsystems:

ccBPF — compiler and virtual machine
CSC — distributed communication stack
RTOS — microkernel runtime
FS / MG — filesystem and memory management
TcpIp — lightweight network stack
world — unified node abstraction model

Execution Model

Programs run as bytecode inside a VM. At any instruction boundary:

Registers, stack, and program counter can be serialized
The state is transferred to another node
Execution resumes at the exact point of suspension

Hardware Setup

The demo uses:

Raspberry Pi Pico 2W (source node)
STM32F103C8T6 with 20 KB RAM (target node)

Result

During the demonstration:

The program produces output on the source MCU
Execution is suspended at runtime
The VM state is transferred to the target MCU
Execution continues seamlessly on the target
Output remains correct and continuous

Repository Structure

ccBPF   - language and virtual machine
CSC     - distributed communication stack
fs      - filesystem
mg      - memory management
RTOS    - microkernel
shell   - interactive shell
TcpIp   - network stack
world   - unified node abstraction

Current Status

LTTit is a research prototype focused on:

Execution mobility on constrained devices
Language‑level distributed execution
Bare‑metal MCU interoperability

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