HeartOS – A POSIX-based Hard Real-time Operating System



HeartOS from DDC-I is a POSIX-based hard real-time operating system that is fast, light and well featured for most for small to medium embedded applications, including safety-critical applications. It is a compliment to DDC-I’s time & space RTOS, Deos™, which is suited for applications that can benefit by multiple assurance levels and space partitioning. HeartOS was designed to operate on 16-bit and 32-bit platforms, however it is configurable without the POSIX layer for memory constrained systems.




  • HeartOS-Architecture-GraphicModular & Scalable
  • POSIX Profile 51 Style Interfaces
  • Small Footprint
  • Certifiable to DO-178, Level A
  • Supports 32 / 16 bit processors and DSP's
  • Network Support
  • Provides the required POSIX Interfaces
    • Implemented using the provided core services
  • Implemented using the provided core services
  • Initialization Interfaces
    • Initializes pre-allocated kernel and internal data structures
    • Allows configuration of many of the provided services, including number of threads, stack size, priorities, etc.
  • Run-time interfaces
    • Provides an interface for the BSP to notify the OS that a system time tick has occurred
    • Provides hooks for the BSP to notify the OS of exceptions or interrupts which have occurred
Components and Target Support Components
  • POSIX Profile 51 Interfaces
  • TCP/IP Stack
  • Optional DO-178 Certification Artifacts
  • OpenArbor Tool Chain

Target Support

  • x86 (386, 486, Pentium)
  • PowerPC (5xx, 55xx, 603e, 82xx)
  • ARM (ARM7, ARM9)
  • Others (Call for Availability)
The HeartOS Core
    • Provides framework to host the POSIX API
    • Includes thread and list services as well as the interrupt and exception interface and the signal frame
  • Highly Configurable
    • Conditional compilation used to completely remove modules which may not be required (e.g. signals)
    • Reduces the footprint
  • Deterministic response

All services designed to have a deterministic response time

  • Scalable
    • Kernel services designed to be scalable from 16 to 32 bit
BSP and Networking
  • Provides platform specific initialization of the hardware platform, including: timers, interrupts, and exceptions
  • Initializes the HeartOS
  • Forwards OS time tick interrupts to the OS
  • Forwards unhandled interrupts or exceptions to the OS as necessary
The Hardware Abstraction Layer
  • Provides an abstract interface to the processing core
  • Simplifies porting to new processors
  • Processor specific thread creation and context switching
  • Interrupt enable/disable services
  • Considered part of BSP
Networking Features
  • Low RAM Usage
    • May be as low as 10K
  • Low Footprint
    • 40Kb
  • Standard BSD
    • Supports standard BSD socket interface for network
  • Configurable
    • Protocol components such as ARP, UDP, TCP, ICM can be conditionally compiled. Each of the components expose useful set of configurable options
  • Portable
    • The TCP/IP stack interfaces with the device driver through a Network Abstraction Layer
  • Zero Copy
    • The TCP/IP stack uses a network buffer management similar to BSD mbufs to achieve optimum zero copy architecture
  • Deterministic
    • All algorithms in the TCP/IP stack are bounded
  • Standards Compliance
    • The implementation conforms to RFCs 791, 792, 768, 793 et al
  • Open Source
    • HeartOS TCP/IP stack is derived from the Light Weight TCP/IP stack (LWIP), which is quite actively developed by the Open Source Community and deployed in a wide range of products