AD5940 Body Impedance Analysis (BIA) on nRF5340 DK

This project demonstrates how to interface the Analog Devices AD5940 high-precision impedance analyzer with a Nordic nRF5340 DK using Zephyr RTOS over SPI. It performs Body Impedance Analysis (BIA) measurements and outputs results over UART.

Built as a reference example for university embedded-systems courses.

Hardware Setup

    nRF5340 DK (Arduino Header)              AD5940 Eval Board
   ┌──────────────────────────┐             ┌─────────────────┐
   │                          │             │                 │
   │  D13 (P1.15) SCK  ──────┼─────────────┼── SCK           │
   │  D11 (P1.13) MOSI ──────┼─────────────┼── MOSI          │
   │  D12 (P1.14) MISO ──────┼─────────────┼── MISO          │
   │  D10 (P1.12) CS   ──────┼─────────────┼── CS            │
   │  D2  (P1.04) INT  ──────┼─────────────┼── GP0 (INT)     │
   │       P0.07  RST  ──────┼─────────────┼── RESET         │
   │                          │             │                 │
   │  GND ────────────────────┼─────────────┼── GND           │
   │  VDD (3.3V) ────────────┼─────────────┼── VDD           │
   │                          │             │                 │
   └──────────────────────────┘             └─────────────────┘

Pin Connections

Function	nRF5340 Pin	Arduino Header	AD5940 Pin	Notes
SCK	P1.15	D13	SCK	SPI clock
MOSI	P1.13	D11	MOSI	SPI data out
MISO	P1.14	D12	MISO	SPI data in
CS	P1.12	D10	CS	Manual GPIO, active low
INT	P1.04	D2	GP0	Interrupt, active low, pull-up
RST	P0.07	--	RESET	Active low
GND	GND	GND	GND	Common ground
VDD	3.3 V	3V3	VDD	Power supply

SPI uses the SPIM2 peripheral (not SPIM4). Chip select is driven manually via GPIO rather than through the SPI controller.

Prerequisites

• nRF Connect SDK (v2.5.0 or later) with Zephyr RTOS
• west meta-tool (installed as part of the nRF Connect SDK)
• nRF5340 DK development board
• AD5940 or ADuCM355 evaluation board
• A USB cable for programming and UART console output

Build and Flash

1. Set up the nRF Connect SDK environment (see Nordic's installation guide).

2. Build the project:

   west build -b nrf5340dk/nrf5340/cpuapp

3. Flash the firmware:

   west flash

4. Open a serial terminal (115200 baud) to see measurement output:

   # Example using minicom
   minicom -D /dev/ttyACM0 -b 115200

To build for the non-secure target (with TF-M), use the nrf5340dk/nrf5340/cpuapp/ns board target instead. The corresponding device tree overlay is selected automatically via CMakeLists.txt.

Repository Structure

├── CMakeLists.txt              Build configuration
├── prj.conf                    Kconfig options (SPI, GPIO, logging, FPU)
├── boards/                     Device tree overlays for nRF5340 DK
├── src/
│   ├── main.c                  Entry point: initializes AD5940 and runs BIA loop
│   └── ad5940/
│       ├── ZephyrPort.c        Platform port: SPI, GPIO, delay, interrupt
│       ├── AD5940Main.c        Application-level init and measurement sequencing
│       ├── BodyImpedance.c     BIA algorithm configuration and result processing
│       ├── ad5940.c / ad5940.h Vendor library (Analog Devices)
│       └── ...                 Additional vendor headers
├── docs/                       Project documentation
│   ├── PRD.md                  Product requirements document
│   ├── architecture.md         System architecture and data flow
│   └── porting-guide.md        Guide for porting AD5940 to new platforms
├── project-template/           Starter template for student assignments
└── llm-context/                Nordic course material (reference for AI tools)

For detailed design documentation, see:

• docs/porting-guide.md -- How to port the AD5940 library to a new Zephyr-based platform.
• docs/PRD.md -- Product requirements and project scope.
• docs/architecture.md -- System architecture, component interactions, and data flow.

Student Template

The project-template/ directory contains a stripped-down version of this project intended as a starting point for course assignments. It includes the build scaffolding and vendor library but leaves the port layer and application logic for students to implement.

License

See individual source files for license information. The AD5940 library files are provided by Analog Devices.