VitalSense – Part 11 : Research Workstation System Architecture

4. Detailed Layer Description

Layer 1: Physical / Sensor Layer (Hardware)

• MAXREFDES117:

  • Interface: I2C.

  • Measured Quantities: Raw reflected/absorbed light intensity for Red and Infrared wavelengths.

  • Function: Provides raw optical data required to reconstruct the PPG waveform, calculate HR, and derive SpO2

• MAX30208EVSYS:

  • Interface: I2C.

  • Measured Quantities: High-resolution digital body temperature (20-bit ADC).

  • Function: Delivers stable, continuous skin temperature measurement.

Layer 2: Conversion & Transmission (Embedded Firmware)

• Microcontroller Tasks:

  1. Polls the MAX30102 FIFO registers and MAX30208 temperature registers at a configurable sampling rate (100 Hz – 400 Hz for PPG).

  2. Applies precise timestamps to each assembled data packet.

  3. Formats frame payloads (e.g., [HEADER][TIMESTAMP][RED][IR][TEMP][CHECKSUM]).

  4. Transmits framed data over USB CDC (Virtual COM Port).

Layer 3: Acquisition & Analysis Engine (LabVIEW Backend)

• Acquisition: Utilizes NI-VISA to read incoming serial streams from the COM port and unpack channels.

• Digital Signal Processing (DSP):

  • Filtering: Bandpass filtering (Butterworth, e.g., 0.5–5.0 Hz) to eliminate motion artifacts, baseline wander (respiration), and high-frequency noise.

  • HR/HRV Algorithm: Detects PPG waveform peaks to determine peak-to-peak (RR/PP) intervals and Heart Rate Variability (HRV).

  • ${\text{SpO}}_2$ Algorithm: Computes the AC/DC ratio of Red vs. IR signals

    

    to evaluate blood oxygen saturation levels.

  • Archiving: Streams raw and processed signals into binary TDMS files optimized for high-speed time-series data.

• IPC Interface: Serves processed metrics to the Qt desktop app in real time via a local TCP/IP socket.

Layer 4: User Interface & Database Layer (Qt Desktop UI)

• TCP/IP Client (QTcpSocket): Receives data packages from the LabVIEW server.

• Visualization (GUI):

  • Real-time rendering of PPG waveforms and temperature trends via plotting widgets (QCustomPlot / Qt Charts).

  • Numerical LCD/Gauge indicators for HR, SpO2​, and Temperature.

• Database Management (Qt SQL):

  • Session cataloging linked to patient IDs, timestamps, and clinical notes.

• Business Logic:

  • Two-tier alarm thresholds (Warning / Critical) monitoring for bradycardia, tachycardia, hypoxia, or fever.

  • Automated generation of session summary reports (PDF export).

5. Data Flow Summary

1. Sensors continuously capture optical reflection and temperature readings.

2. Microcontrollers aggregate I2C data, timestamps packets, and streams frames over USB.

3. LabVIEW receives the stream, parses channels, filters noise, and computes physiological parameters.

4. Qt Application receives processed parameters over IPC, displays real-time plots, alerts operators to anomalies, and logs records to the database.

6. Summary of Subsystem Integration