Data Processing

The data-processing layer turns ADC samples and sensor updates into board values that the rest of the firmware can trust. It is where the CAN-Gateway cleans up noisy measurements, keeps the runtime sensor objects fresh, and decides when the board has enough data to move on.

The core implementation is found in repos/CAN-Gateway/Core/Src/App/DataProcessing/data_processing.c with header definitions in repos/CAN-Gateway/Core/Inc/App/DataProcessing/data_processing.h.

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Signal Processing & Safety Gating

Kalman Filtering (kalman_takasu)

To filter out severe electro-magnetic interference (EMI) and power bus ripple, all continuous analog measurements are fed into a Kalman filter state-space tracker (kalman_takasu).

• Mathematical Model: The system propagates state estimates and covariance matrices using the state-transition matrix $\mathrm{\Phi }$, control distribution matrix $G$, and process noise covariance $Q$:$$x_{k|k-1}=\mathrm{\Phi }{x}_{k-1|k-1}$$$$P_{k|k-1}=\mathrm{\Phi }{P}_{k-1|k-1}{\mathrm{\Phi }}^T+GQ{G}^T$$
• Chi-Squared (${\chi }^2$) Outlier Rejection: A statistical threshold test validates each incoming measurement before correction. If a sample $z_k$ deviates too far from the predicted state $x_{k|k-1}$ such that:$$(z_k-H_t{x}_{k|k-1}{)}^2>{\chi }_{limit}^2$$the filter flags an outlier rejection (kalman_status = 2). The measurement is discarded, preventing noise spikes or EMI from corrupting the system's filtered estimation.

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APPS Safety Validation

The Accelerator Pedal Position Sensors (APPS) are safety-critical. The driver executes strict validation checks in the is_apps_valid function in repos/CAN-Gateway/Core/Src/App/DataProcessing/data_processing.c before forwarding displacement percentages:

1. Voltage Bounds Gating: Raw ADC voltages must fall strictly between $0.5\text{ V}$ and $4.5\text{ V}$ (assuming a $3.3\text{ V}$ reference on the 12-bit ADC). Raw readings outside these limits indicate a short circuit or open circuit condition.
2. Implausibility Divergence: The normalized readings from apps1 and apps2 must not diverge by more than $15\mathrm{\%}$ of the full-scale range:$$|APP{S}_1-APP{S}_2|\le 15\mathrm{\%}\times AD{C}_{max}$$
3. Fail-Safe Mode: If either boundary is breached, the displacement is immediately overridden to a default fault value of 255. The ECU catches this specific output to trigger a shutdown or power clamp.

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Source & Layout Reference

• repos/CAN-Gateway/Core/Src/App/DataProcessing/data_processing.c: Owns the sensor update routines (process_sensor_data) and the Kalman callback linkages.
• repos/CAN-Gateway/Core/Inc/App/DataProcessing/DP_scheduler_vals.h: Defines update frequencies and schedule constants (e.g. APPS_UPDATE_MS, STEERING_UPDATE_MS).
• repos/CAN-Gateway/docs/modules/data-processing/adc-buffer.md: Tracks DMA mapping setups.

Related Deep Dives

• ADC calculation verification
• DHAB S134 driver reference
• DHAB S134 physical configuration