Hardware & Implementation

Zephyr RTOS

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An open-source real-time operating system with native BLE stack, used by Nordic's nRF Connect SDK and many BLE SoC vendors.

    


    
    
    

      Also known as:
      
      Zephyr
      
      Zephyr OS
      
    

    
  


  




  
  

    
Zephyr RTOS


Zephyr is an open-source, vendor-neutral real-time operating system (RTOS) with a native, fully integrated BLE protocol stack. Maintained by the Linux Foundation, Zephyr has become the de facto standard RTOS for BLE product development, adopted by Nordic Semiconductor's nRF Connect SDK, Intel, and dozens of other silicon vendors.


BLE Stack Architecture


Zephyr's BLE implementation includes both host and controller components:


    

  • Controller: Link Layer, PHY management, advertising engine, connection state machine. Runs as a high-priority thread with deterministic timing
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  • Host: L2CAP, ATT, GATT, SMP, GAP. Runs as application-context threads with callback-based APIs
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  • HCI driver: Connects host and controller via in-process function calls (single-chip) or UART/SPI transport (dual-chip like nRF5340)
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The stack supports BLE 5.4 features including Extended Advertising, Periodic Advertising, Direction Finding, LE Audio (CIS/BIS), and Connection Subrating.


Key Features for BLE Development


Zephyr provides several capabilities critical for BLE firmware:


    

  • Kconfig: Fine-grained compile-time configuration of the BLE stack (disable unused features to save flash/RAM)
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  • Devicetree: Hardware description for multi-board portability
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  • Bluetooth Shell: Interactive command-line interface for testing BLE operations without custom firmware
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  • Logging subsystem: Structured logging with SoC with antenna on a PCB." data-category="Hardware & Implementation">module-level filtering
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  • MCUboot integration: Secure bootloader for OTA firmware updates
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  • Bluetooth Mesh: Full Bluetooth Mesh 1.1 support including Directed Forwarding
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Supported Hardware


Zephyr supports over 600 boards, including all major BLE SoC families:



Getting Started


The typical Zephyr BLE development workflow involves:


    

  1. Install the Zephyr SDK and west meta-tool
    2. 

  2. Select a sample application (e.g., samples/bluetooth/peripheral_hr)
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  3. Configure via prj.conf (Kconfig) and board-specific overlay
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  4. Build: west build -b nrf52840dk/nrf52840
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  5. Flash: west flash
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  6. Debug: west debug or RTT console
    7. 



For teams already using Nordic chips, the nRF Connect SDK (which is built on Zephyr) provides Nordic-specific additions including Bluetooth qualification listings, power optimization libraries, and production-quality LE Audio support.

  

  

  
  
  




  
  
Related Terms

  

  

    
    SDK
    
    FreeRTOS
    
  





  

  
  

  
  

  
  
  

    
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Frequently Asked Questions


  

    
    

      
      

        
Our glossary covers 90+ BLE technical terms organized by category. Each term includes a definition, related terms, and links to relevant chips and guides.