The SALAR-Bio-DAQ is a comprehensive hardware and software ecosystem designed for high-speed, closed-loop cardiac tissue conditioning and electrophysiological signal analysis.
The most significant architectural achievement of the SALAR software suite (both Online and Offline) is its strict adherence to pure time-domain signal processing.
- No History Dependency: The algorithms calculate biological markers (like MAP, Contraction, and APD80) instantaneously based on current states, without relying on long historical signal buffers.
- No Frequency Domain (No FFT): By eliminating computationally heavy frequency-domain transformations (like FFT), the system achieves true zero-latency, real-time plotting and closed-loop feedback.
- PHOSITA Note: Researchers and engineers can review the raw Delphi source codes to see exactly how these real-time, history-independent algorithms are implemented from scratch.
The SDC-1721 is a high-performance, multi-channel hardware interface designed for Closed-Loop Cardiac Tissue Conditioning. It serves as both the sensory input for bio-signals and the precision actuator for electrical stimulation.
- Continuous Operation (Dual-Battery Switching): Unlike standard isolated stimulators (e.g., A365) that require manual recharging, the SDC-1721 features an intelligent internal switching circuit with two batteries. One battery powers the system while the other charges simultaneously.
- Long-Term Stability: This design allows the device to remain powered on for extended periods (tested up to one month or more), making it ideal for chronic tissue conditioning or long-duration pharmacological studies.
- Intelligent Switching: A specialized relay system handles the transition between batteries to ensure zero data loss or stimulation dropouts during long-term tests.
- Dual USB Architecture: The system uses two dedicated USB connections via specialized, secure-locking DB-9 to USB cables to prevent accidental disconnection.
- Data Acquisition (DAQ) Port: Dedicated high-speed stream for analog inputs.
- Stimulator Control Port: Dedicated command line for real-time pulse adjustment.
- Multi-Chamber Scalability: The stimulation output is designed to be split, allowing a single SDC-1721 unit to drive multiple incubators or tissue baths simultaneously.
- Standardized I/O: BNC connectors for Impedance Spectroscopy and Stimulation outputs ensure compatibility with existing laboratory sensors and electrodes.
- 6-Channel Analog Acquisition: Supports +/- 10V input ranges (Channels 0–5).
- Closed-Loop Control: Real-time measurement of physiological parameters to dynamically adjust stimulator output (e.g., changing pulse width/current based on tissue response).
- Stimulation Flexibility:
- Internal: Built-in unipolar stimulator.
- External: TTL and Analog V-Control/I-Control for external amplifiers (WPI A365/A395).
🤝 Collaboration Note: The SDC-1721 was engineered to bridge the gap between simple DAQ boards and high-end medical-grade conditioners. The internal logic handles the "heavy lifting" of power isolation and safety, allowing the software to focus entirely on high-level signal processing.
The online software suite for the SDC-1721 is divided into two highly synchronized modules: the DAQ Engine and the Protocol Stimulator.
This module handles high-speed data acquisition using our proprietary time-domain algorithms.
- Closed-Loop Verification (Capture Detection): The software calculates the signal period in real-time. By comparing the heart's response period to the stimulation period, it provides an immediate visual confirmation of "Cardiac Capture".
- Real-Time Digital Filtering: Features adjustable FIR Low-Pass filters critical for noise rejection in raw MAP signals before calculating sensitive parameters like APD80.
- Live Restitution Analysis: Calculates APD (Action Potential Duration) and DI (Diastolic Interval) on-the-fly using two distinct time-domain algorithms:
- Stimulus-Dependent: Uses the stimulus artifact as a temporal anchor.
- Stimulus-Independent: Purely signal-driven analysis for cases where the artifact is suppressed.
- Multi-Channel Visualization: Allows users to overlay stimulation pulses directly onto bio-signal channels (e.g., MAP) to visualize phase-locking in real-time.
A sophisticated pulse generator designed for complex pacing protocols.
- Dynamic Protocol Engine: Build and save multi-stage protocols (e.g., WBCL - Wenckebach Cycle Length, S1-S2 recovery, or fatigue).
- Parameter Agility: Real-time adjustment of BCL (Base Cycle Length) from 30ms to 500ms without interrupting the experiment.
- Software-Controlled Current: Integrated current control (0-10mA or 0-100mA) eliminates manual potentiometer adjustments, enabling fully automated remote experiments.
- Safe Transition Logic: When a programmed protocol ends, the system automatically reverts to a safe "Base BCL" to prevent cardiac arrest.
The Source directory contains two primary implementation paths:
- Status: Stable / Fully Validated
- Description: Stand-alone logic for DAQ and Stimulation used during the majority of Langendorff studies. Features reliable real-time APD80 marking without inter-module dependency.
- Status: Experimental / Ongoing Research
- Description: The Synced Closed-Loop Version where DAQ and Stimulator modules communicate directly to automatically adjust pacing based on sensed MAP responses.
⚠️ Validation Note: Due to COVID-19 laboratory closures and the interruption of remote-debugging sessions at Prof. Khori’s Ischemic Disorder Lab, formal validation of this closed-loop feedback is incomplete. It is provided as a high-level framework for PHOSITA-level researchers.
This repository contains advanced physiological signal analysis tools developed purely in Delphi 7. These tools prototyped the time-domain algorithms later integrated into the Online DAQ.
- Zero Dependency: Built from the ground up without external libraries to ensure maximum execution speed.
- Time-Domain Focus: No FFT required. Deeply optimized for detecting features in Monophasic Action Potentials (MAP), Contractions, and ECGs using strict history-independent logic.
- Research-Validated: All algorithmic outputs (APD, DI, and Pacing intervals) have been cross-validated against ADInstruments LabChart (PowerLab) with near-identical results.
- Arrhythmia Package (
/Arythmia Package): Detection and categorization of cardiac events (VT, VF, PVC) to calculate overall "Cardiac Scores." - Complete Signal Score Calculator (
/Compelete Signal Score Calc): Semi-automated "Right-Click" interface for rapid marking of Ventricular Tachycardia (VT) or Fibrillation (VF) segments. Exports to.txtand Excel. - Restitution Calculator (
/Delphi (VF-VT) New APD-DI): High-precision calculation of APD and DI. Includes a custom "Professional Charting" engine for plotting Restitution Curves. - Event Manager & Auto-Trim (
/Score Calc - Event Manager): High-volume data management that automatically trims large datasets based on stimulus artifacts.
📊 Validation Standard: A Sample Standard folder is provided containing raw LabChart .txt exports. PHOSITAs can use this data to test the Delphi source code and verify the accuracy of the APD80 time-domain markers against commercial standards.
- User Management: The source code contains a legacy security layer (Username/Password) used originally for student activity logging.
- PHOSITA Instructions: Since full source code is provided, this layer can be easily bypassed or removed for standalone research use.
- Code State: The code is provided in its functional "Research State"—validated for scientific accuracy, though not strictly optimized for "Clean Code" formatting conventions.
Hardware & Connectivity:
Online Software (Instructional Context):
- Video 3: DAQ Software (Real-Time Filtering & Restitution)
- Video 4: Stimulator Software (Building WBCL Protocols)
Offline Signal Processing: