House of the QR Code™ Biofeedback Logger — CYD + Polar H10 Edition: A Proprietary Embedded System for Offline Heart-Rate Variability Visualization

The House of the QR Code™ Biofeedback Logger — CYD + Polar H10 Edition is a proprietary, stand-alone biofeedback system designed for offline heart-rate variability (HRV) monitoring and real-time color visualization. Built on the ESP32-2432S028R (“CYD”) microcontroller platform and paired with the Polar H10 ECG-grade heart sensor, this embedded device automatically connects via Bluetooth Low Energy (BLE), captures RR-interval data, computes rMSSD on-board, and displays physiological balance using a color-coded interface: 🟩 Calm, 🟨 Balanced, 🟥 Stressed. Unlike mobile HRV apps or cloud-linked monitors, the Biofeedback Logger operates entirely offline, ensuring user privacy and data security. All measurements are locally recorded to microSD storage (/H10_LOG.csv) with timestamps, heart rate (bpm), RR interval (ms), and rMSSD (ms). The internal firmware is proprietary to House of the QR Code™ and employs optimized BLE handling and HRV computation algorithms for smooth, real-time performance on resource-constrained hardware. The system demonstrates how embedded wellness technology can provide accessible, low-cost, and privacy-preserving HRV monitoring for applications in: Mindfulness and stress reduction Sports recovery and performance tracking Clinical pilot studies and wellness research STEM and biofeedback education environments This preprint documents the device’s design principles, signal-processing methods, and human-centered visualization approach, contributing to the growing field of physiological computing and embedded biofeedback systems. Author: Tyrone M. Sanders Affiliation: House of the QR Code™ Contact: houseoftheqrcode@gmail.com