Introduction to Zephyr & Nordic SoC

BME554L - Fall 2025

Dr. Mark Palmeri, M.D., Ph.D.

Duke University

August 25, 2025

Why Firmware?

Firmware isn’t “software”…

• Firmware is a special kind of software that is designed to interact with hardware.
• Firmware is often written in C, but can be written in other languages.
• Firmware is highly resource constrained
• Software is often written in Python, Java, C++, etc.
• Software is often written to be run on a general-purpose computer (laptop, desktop, server, etc.), that typically is not resource constrained.
  • User Interface
  • Web Server
  • Database
  • Data Processing / Analytics

Medical Device Examples

Zephyr RTOS

What is Zephyr?

https://www.zephyrproject.org/

Why Zephyr?

• Completely open-source RTOS supported by the Linux Foundation
• Quickly becoming the default RTOS for many embedded device companies (e.g., Nordic Semiconductor)
• 100% C-based language; CMake build system; Python-based framework (west)
• Online community growing fast

C Programming Language

• Zephyr is written in C
• CMake build system
• West CLI tools
• We will use an incredibly powerful Visual Studio Code IDE extension pack, nRF Connect developed by Nordic Semiconductor.

Bare Metal vs. RTOS

• Bare-metal super-loop implementations
• Realtime Operating System (RTOS)
• Interupt Service Routines (ISR) / Callbacks

System on a Chip (SoC)

What is a System on a Chip (SoC)?

• CPU
• Memory (RAM) - quite limited
• I/O
• Storage (non-volatile)
• RF / Communication Protocols
  • Universal Asynchronous Receiver-Transmitter (UART)
  • Inter-Integrated Circuit (I2C)
  • Serial Peripheral Interface (SPI)
  • Bluetooth Low Energy (BLE)

This is in contrast to a motherboard-based personal computer, which uses additional discrete components or expansion / peripheral cards.

Nordic nRF52833 Development Kit (DK)

https://youtu.be/KOWo9P1qdfk