Project Documentation Project: BioSense DT337C VT25 Fakhra Munawar, Mohid Ali

1. Project Overview 1.1 Purpose of the system The BioSense BLE-enabled Multi-Sensor Monitoring System is developed to monitor physiological signals (ECG and motion) using a compact and energy-efficient setup. The system utilizes Bluetooth Low Energy (BLE) to wirelessly transmit real-time sensor data to a mobile device. The sensors are embedded in two separate units: • An ECG module (AD8232) placed on the chest to record heart activity. • A motion sensor (MPU6050) attached to the wrist or leg to detect body movement. The system is designed to: • Optimize power consumption using the low-power capabilities of the nRF52840 microcontroller. • Ensure reliable data communication over BLE. • Enable users to monitor sensor values through nRF Connect, a mobile app available on Android and iOS. • Support basic medical and fitness observation use cases, especially in remote or low-resource environments. 1.2 Summary of Hardware and Software Integration Hardware Integration: • nRF52840 Development Kit: Central microcontroller with BLE support, responsible for collecting and transmitting sensor data. • AD8232 ECG Sensor: Measures electrical signals from the heart; connected to analog and digital input pins on the nRF52840. • MPU6050 Accelerometer/Gyroscope: Captures motion data; communicates via I2C interface with the microcontroller. • Power Supply (3.3V): Powers both sensor nodes efficiently to support low-power operation. • Electrodes and wiring: Properly placed to capture physiological signals effectively. Software Integration: • Developed using Segger Embedded Studio and the nRF5 SDK. • BLE profiles and characteristics configured to stream ECG and motion data in real time. • Compatible with nRF Connect Mobile App, which receives and displays data on Android (BLE 4.3+) and iOS (BLE 5.0+) devices. • Includes simple data handling logic for connection, notification, and sensor data parsing.
2. System Architecture
3. Hardware Design 3.1 List of Components • NRF52840-DK (Nordic Semiconductor) x 2. [1] • MPU-6050 (DFRobot). [2] • AD8232 (SparkFun Electronics). [3] • Power Profiler Kit II (Nordic Semiconductor). [4] • 3.7V Lithium Battery • USB to Micro-USB Cable x 3 • 3-Pin Electrode Cable • Biomedical Electrode • Jumper Wires

3.2 Schematic Diagram Diagram 1: Shows the schematic diagram of nRF52840 and AD8232 Pin Connections

3.3 Wiring and Connections Figure 1: Shows the connection between nRF52840 and AD8232 Sensor

Figure 2: Shows the connection between nRF52840 and MPU6050

4. Software Design 4.1 Programming Environment • Segger Embedded Studio 8.22a. [5] • NRF Connect for Desktop [6] • NRF Connect for Mobile 4.2 Firmware Structure • BLE Stack Initialization: o nrf_sdh_ble.h, ble_advdata.h, ble_advertising.h: Sets up BLE advertising, GAP parameters, and services. o Device name: “Accel_sensor”, “ECG Sensor” o Advertising interval: 300 units (~187.5ms) • GATT, Peer Manager, and Security: o GATT Configuration: nrf_ble_gatt.h o Security settings: bonding enabled, no MITM o Peer manager used for handling bonded devices • Timers and Power Management o App timer: app_timer.h o Power management via nrf_pwr_mgmt.h • Custom BLE Service: BLE_ACCEL_SERVICE o Created using ble_accel_service.h o Sends motion data over BLE notifications when a connection is active o CCCD is checked before sending notifications to ensure client subscribed • Connection and GATT Events o Handles BLE Connection, disconnection and MTU negotiation • Peer Manager Events o Handles bonded device data and re-connections • Advertising and Bond Management o Starts advertising on boot unless bond deletion is requested o Bonded peer data can be erased for testing or pairing with a new device • Logging and Debugging o Enabled via nrf_log.h, nrf_log_ctrl.h o Logs connection status, MTU updates, and accelerometer output. 4.3 Git Repository URL

5. Mobile App Integration
6. Using nRF Connect App
7. Search for Device name: “Accel_sensor”
8. After connecting, upload “1 or on” to UUID 2902.
9. Observe UUID: “00001234-1234-5678-1234-56789ABCDEF0”, starts sending value.
10. Open Log tab to monitor RSSI, and Sensor values.
11. Export/Save data in different formats (CSV, Text)

Bibliography

[1] “nRF52840-DK Product Details,” Nordic semiconductor, [Online]. Available: https://www.nordicsemi.com/Products/Development-hardware/nRF52840-DK. [2] “Digikey, website for order product & Datasheet of product,” DFRobot, [Online]. Available: https://www.digikey.com/en/products/detail/dfrobot/SEN0142/6588492. [3] “Digikey, Analog front end for ECG datasheet and product,” Sparkfun Electronics, [Online]. Available: https://www.digikey.com/en/products/detail/sparkfun-electronics/12650/5824153. [4] “Nordic Semiconductor, Documentation & Certification with key features,” Nordic Semiconductor, [Online]. Available: https://www.nordicsemi.com/Products/Development-hardware/Power-Profiler-Kit-2. [5] “Embedded Segger Studio download website,” Segger, [Online]. Available: https://www.segger.com/downloads/embedded-studio/. [6] “nRF Connect for Desktop, Cross-platform development software for Nordic Products,” Nordic Semiconductor, [Online]. Available: https://www.nordicsemi.com/Products/Development-tools/nRF-Connect-for-Desktop.