41 lines
2.0 KiB
Markdown
41 lines
2.0 KiB
Markdown
# Car telemetry and retention
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The Pi samples the MG4 every 10 seconds while ADB is enabled. Gear and steering angle
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come from the verified ArcSoft properties. Battery values, range, and speed are read
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directly from the factory SAIC vehicle Binder service by a bundled read-only DEX probe:
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```bash
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adb push server/assets/car-telemetry-probe.dex /data/local/tmp/pi-car-telemetry-probe.dex
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adb shell CLASSPATH=/data/local/tmp/pi-car-telemetry-probe.dex \
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app_process /system/bin cloud.molberg.picarprobe.CarTelemetryProbe
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```
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The helper is not installed and has no dependency on MG Utility. It performs only known
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getter transactions. If the factory service is unavailable, battery fields remain
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unavailable while the ArcSoft signals and their history continue working.
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## Storage limits
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- Raw 10-second samples are retained for 90 days and capped at 800,000 rows.
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- Hourly rollups are retained for 10 years and capped at 88,000 rows.
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- Lifetime counters and observed records survive raw-data pruning.
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- Graph endpoints use indexed time buckets and return compact aggregates rather than
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every raw sample.
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At the configured interval the raw cap is approximately 90 days. Expected storage is
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well below 150 MB, although SQLite page allocation and filesystem details can vary.
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## Derived statistics
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- Tracked distance integrates consecutive speed samples no more than 60 seconds apart.
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- The dashboard's range estimate uses tracked distance per observed SOC consumed. It
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waits for at least 10 km and 5 percentage points of discharge before showing a value.
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- Charging power is an estimate based on SOC gain over a 2-10 minute window and the
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MG4 Luxury 2022 usable-capacity assumption of 61.7 kWh. It is deliberately labeled as
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estimated and is capped at 350 kW to reject corrupt samples.
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- Peak values mean the highest value observed at a 10-second sampling point. They are
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not guaranteed to capture a shorter event between samples.
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The collector sends no vehicle-control calls. Enabling and authorizing ADB remains a
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parked-vehicle administration task.
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