From FSR Film to Engineering Dashboard: A Practical Signal Chain for FSR Data

Engineering illustration · FSRTEK technical reference

1. Architectural Overview: The 5-Layer Signal Chain

Directly coupling ADC read routines to user-interface graphics leads to dropped packets, timing jitter, and software fragility. FSRTEK recommends a modular, decoupled architecture structured into five distinct operational tiers:

2. Ingestion & Packet Framing Protocol

To guarantee zero packet loss over serial or wireless channels, edge acquisition boards stream fixed-frame binary packets with robust boundary detection:

3. Calibration & Non-Linear Transformation Pipeline

Raw ADC integer codes are converted into calibrated physical force units ($text{N}$, $text{g}$, $text{kg}$, or $text{kPa}$) through a standardized numerical transformation pipeline:

1. Voltage / Conductance Conversion: Convert raw ADC code $D_{adc}$ into measured conductance $G_{meas} = frac{1}{R_{FSR}}$.
2. Baseline Zero Subtraction: $G_{active} = max(0, G_{meas} – G_{tare})$, removing initial mechanical pre-load offsets.
3. Multi-Segment Piecewise Linear (PWL) Interpolation: Because FSR response varies across light, medium, and saturation regimes, a 5-point to 10-point piecewise linear lookup table provides high-speed conversion on embedded MCUs without floating-point polynomial overhead:

   $$F(G) = F_k + frac{F_{k+1} – F_k}{G_{k+1} – G_k} cdot (G – G_k) quad text{for } G in [G_k, G_{k+1})$$

4. Power-Law Curve Fitting (High-Level SDK): For PC/cloud analytics, apply a calibrated three-parameter power-law fit: $F = a cdot G^b + c$.

4. Multi-Tier Feature Extraction & Event Detection

The processing layer extracts actionable engineering parameters in real time:

• Peak Force & Impact Impulse: Integration of force over contact duration $J = int_{t_0}^{t_1} F(t),dt$, essential for athletic strike and crash analytics.
• Center of Force (CoF) / Center of Pressure (CoP): Dynamic 2D spatial coordinate calculation for balance plates and smart insoles:

  $$X_{CoP} = frac{sum (x_i cdot F_i)}{sum F_i}, quad Y_{CoP} = frac{sum (y_i cdot F_i)}{sum F_i}$$

• Threshold Trigger & Debounce Engine: Dual-threshold Schmitt trigger logic prevents chattering on mechanical contact boundaries.