Rear vehicle radar extension for Hammerhead Karoo. Reads ANT+ radar data and delivers real-time visual and sound alerts — designed to keep your eyes on the road, not the screen.
Features • Installation • Quick Start • Data Fields • Alerts • Settings • Night Mode • FIT Recording • Statistics • Radars • Development
| Feature | Description |
|---|---|
| 3 Data Fields | Compact, Standard, Full — graphical Glance widgets for any ride screen layout |
| Multi-channel Alerts | Visual banner + escalating sound patterns via Karoo speaker |
| 4 Sound Sets | Classic, Subtle, Urgent, Bike Bell — choose what fits your riding style |
| Threat Levels | Approaching, Warning, Critical — color-coded with configurable distance thresholds |
| Night Mode | Automatic threshold increase after sunset (GPS-based detection) |
| Closing Speed Detection | Fast-closing vehicles auto-escalate; holding/receding vehicles suppressed |
| Traffic Density Adaptation | Sustained heavy traffic silences minor alerts; dangerous vehicles still break through |
| Speed Gate | Suppress minor alerts when stopped or slow — critical alerts always fire |
| Alert Cooldown | Smart repeat delay prevents alert fatigue without missing new threats |
| Escalation Bypass | Higher threat levels fire immediately, ignoring cooldown |
| FIT Recording | Threat level, vehicle count, and nearest distance written to ride file at 1 Hz |
| Ride Statistics | Per-ride stats: alert counts, closest approach, max vehicles, threat time |
| Quick Mute | Toggle alerts via physical button or remote — data fields keep updating |
| Screen Wake | Wake Karoo screen on critical threats or any threat |
| Imperial / Metric | Automatic unit detection from Karoo profile |
| Fully Offline | No accounts, no cloud, no internet, no phone pairing |
| Open Source | MIT licensed, free forever |
Get the latest release from GitHub Releases or eiradar.com.
# Install via ADB
adb install eiradar.apk
# Or via Hammerhead Companion app:
# 1. Download APK on your phone
# 2. Share to Hammerhead Companion
# 3. Install on KarooPrerequisites:
- Android Studio (JDK 17 bundled)
- GitHub PAT with
read:packagesscope (for Karoo SDK)
Setup:
# Add to ~/.gradle/gradle.properties
gpr.user=YOUR_GITHUB_USERNAME
gpr.key=YOUR_GITHUB_TOKENBuild:
./gradlew assembleReleaseOutput: app/build/outputs/apk/release/eiradar.apk
Connect your ANT+ radar in Karoo Settings > Sensors.
- Open Profiles on Karoo
- Edit a profile > Add data page
- Select More Data > eiRadar
- Choose a layout: Radar (S), Radar (M), or Radar (L)
Alerts fire automatically when vehicles approach from behind. The first launch shows a quick onboarding guide.
Three graphical data types built with Jetpack Glance. Each renders fresh RemoteViews every 1 Hz cycle.
| Data Field | Karoo Name | Content |
|---|---|---|
| Compact | Radar (S) | Vehicle count, colored by threat level |
| Standard | Radar (M) | Vehicle count + nearest distance + status label |
| Full | Radar (L) | Threat label + vehicle count + distance + status message |
All widgets feature a colored status bar at the top (green / orange / red) and a rounded dark background. When alerts are muted, the status bar turns grey and the label shows "MUTED" — radar data continues to display normally.
| State | S display | M / L display |
|---|---|---|
| Not connected | — grey |
"No radar" |
| Connecting | ... grey |
"Connecting" |
| Clear | OK green |
"All clear" / "Road is clear" |
| Threat | count, colored | count + distance in meters / feet |
| Connection lost | ! grey |
"Connection lost" |
| Color | Level | Meaning |
|---|---|---|
| Grey | Disconnected | Radar not paired, connecting, or connection lost |
| Green | Clear | No vehicles detected |
| Orange | Approaching / Warning | Vehicle detected, closing distance |
| Red | Critical | Vehicle very close |
Two independent alert channels. Each can be enabled or disabled separately with a master switch to control all at once.
| Channel | What it does | Default |
|---|---|---|
| Banner | Karoo in-ride visual alert overlay with auto-dismiss | On |
| Sound | Beep patterns via Karoo speaker (4 sound sets) | On |
| Set | Character |
|---|---|
| Classic | Traditional beep patterns — single, double, triple |
| Subtle | Quieter, gentler tones for less intrusive alerts |
| Urgent | Loud, rapid patterns that demand attention |
| Bike Bell | Musical tones using note frequencies |
Alerts follow the threat level hierarchy. When a threat escalates (e.g. Approaching → Warning → Critical), the new alert fires immediately — cooldown is bypassed. De-escalation respects the normal cooldown.
| Level | Banner duration |
|---|---|
| Critical | 5 s |
| Warning | 4 s |
| Approaching | 2 s |
| Clear | 1.5 s |
Optional confirmation sound when all vehicles have passed. Useful as an "all safe" signal before lane changes or turns.
Assign Toggle Radar Alerts to a physical button or remote in Karoo Settings > Controls. One press mutes all alert channels (sound, banner). Press again to re-enable. Ideal for group rides where nearby cyclists trigger false alerts.
- Data fields continue showing live radar data with a "MUTED" indicator
- FIT recording and statistics continue normally
- Auto-unmutes when the ride ends — the next ride always starts with alerts enabled
eiRadar uses closing speed and traffic density to keep the system quiet in normal traffic and loud when actually dangerous. All fully automatic — no settings required.
Closing speed — Smoothed from the last 3 nearest-distance samples at 1 Hz:
- Vehicle closing at ≥36 km/h differential → alert escalated one level (Approaching→Warning, Warning→Critical)
- Vehicle holding distance or receding (≤7 km/h differential) → Approaching alert suppressed
- Large distance jumps (>30 m) reset tracking — different vehicle, fresh calculation
Traffic density — Rolling 30-second average of vehicle count:
- Average ≥2 vehicles sustained for 10+ seconds → Approaching alerts suppressed
- Fast-closing vehicles are escalated to Warning/Critical first, so they bypass density suppression
- Zero-vehicle periods naturally decay the average — alerts return when traffic clears
On a busy road: normal traffic is silent. A fast-closing vehicle gets escalated to Warning → bypasses density suppression AND triggers throttler escalation bypass → immediate alert.
- Critical alerts always fire regardless of speed gate, traffic density, or other suppression
- Repeat delay prevents alert fatigue without missing genuinely new threats
- Escalation bypass ensures worsening situations are immediately communicated
- Quick mute auto-resets on ride end — no risk of starting a ride with alerts off
All settings are accessible from the eiRadar app on Karoo. Tap any value to cycle through options.
| Setting | Options | Default |
|---|---|---|
| Enable alerts | On / Off | On |
| Banner | On / Off | On |
| Sound | On / Off | On |
| Sound set | Classic / Subtle / Urgent / Bell | Classic |
| All-clear sound | On / Off | On |
| Setting | Options | Default |
|---|---|---|
| Approaching | 100 / 125 / 150 / 175 / 200 m | 100 m |
| Warning | 30 / 40 / 50 / 60 / 70 m | 50 m |
| Critical | 10 / 15 / 20 / 25 / 30 m | 20 m |
The radar detects vehicles up to ~140 m. The default 100 m approaching threshold leaves a 40 m "silent awareness" zone where the widget updates but no alert fires — this reduces alert fatigue on busy roads.
| Setting | Options | Default |
|---|---|---|
| Repeat delay | 3 s / 5 s / 8 s / 12 s | 5 s |
| Min speed | Off / 3 / 5 / 8 km/h | Off |
| Wake screen | Never / Critical only / Always | Critical only |
Min speed (speed gate): Only suppresses Approaching alerts below the set speed. Warning and Critical alerts always fire — a stopped cyclist at a traffic light is the most vulnerable.
Available in the settings screen. Clears all preferences and restores factory settings with a confirmation dialog.
eiRadar automatically detects sunset and sunrise using Karoo's GPS-based time data. No manual configuration needed.
When night mode is active, all distance thresholds are increased by 33 % to provide earlier warnings in low-visibility conditions:
| Threshold | Day | Night (+33 %) |
|---|---|---|
| Approaching | 100 m | 133 m |
| Warning | 50 m | 66 m |
| Critical | 20 m | 26 m |
Night mode status is visible on the dashboard screen. The multiplier applies automatically — no settings to change.
eiRadar writes radar data to the Karoo ride FIT file at 1 Hz using developer fields. This data appears alongside your standard ride metrics in any FIT-compatible analysis tool.
| Developer Field | Type | Description |
|---|---|---|
radar_threat_level |
uint8 | 0 = Clear, 1 = Approaching, 2 = Warning, 3 = Critical |
radar_vehicle_count |
uint8 | Number of vehicles currently detected (0–8) |
radar_nearest_distance |
uint16 | Distance to nearest vehicle in meters |
Recording starts and stops automatically with ride recording.
eiRadar tracks per-ride session statistics, stored locally in a Room database:
| Metric | Description |
|---|---|
| Session duration | Total ride time |
| Total alerts | Number of alerts fired across all levels |
| Approaching alerts | Count of approaching-level alerts |
| Warning alerts | Count of warning-level alerts |
| Critical alerts | Count of critical-level alerts |
| Max vehicles | Peak simultaneous vehicle count during the ride |
| Closest approach | Nearest vehicle distance recorded (meters) |
| Threat time | Cumulative time spent under any threat level |
Statistics are shown after ride completion. All data stays on-device.
Any ANT+ cycling radar paired through Karoo sensor settings:
| Radar | Type |
|---|---|
| Garmin Varia RTL515 | Tail light + radar |
| Garmin Varia RTL516 | Tail light + radar |
| Garmin Varia RVR315 | Radar only |
| Bryton Gardia R300L | Tail light + radar |
| Magene L508 | Tail light + radar |
The Karoo receives ANT+ radar data natively. eiRadar reads it from the Karoo SDK's sensor stream — up to 8 vehicles tracked simultaneously with per-vehicle distance data.
| Requirement | Details |
|---|---|
| Device | Hammerhead Karoo 2 or Karoo 3 |
| Radar | ANT+ compatible cycling radar |
| Internet | Not required |
| Account | Not required |
io/github/ykn/variaradarpro/
├── VariaRadarExtension.kt # KarooExtension entry point, FIT recording, BonusAction
├── MainActivity.kt # Compose UI host (settings, onboarding, dashboard)
│
├── engine/ # Core logic
│ ├── RadarEngine.kt # ANT+ radar data → StateFlow<WidgetState>
│ ├── AlertManager.kt # Threat evaluation + alert dispatch + night mode
│ ├── AlertThrottler.kt # Per-level cooldown with escalation bypass
│ ├── ClosingSpeedTracker.kt # Smoothed closing speed → escalation / suppression
│ ├── TrafficDensityTracker.kt # Rolling density window → APPROACHING suppression
│ ├── SoundEngine.kt # Karoo PlayBeepPattern integration (4 sound sets)
│ ├── NightModeManager.kt # Sunrise/sunset detection via Karoo GPS data
│ └── StatisticsCollector.kt # Per-ride session stats aggregation
│
├── datatypes/glance/ # Karoo data fields (Jetpack Glance)
│ ├── GlanceDataType.kt # Base: fresh RemoteViews per 1 Hz cycle, mute state
│ ├── GlanceComponents.kt # Shared: DataFieldContainer, StatusBar, ValueText, LabelText
│ ├── SmallWidgetGlanceDataType.kt # Radar (S) — compact
│ ├── MediumWidgetGlanceDataType.kt # Radar (M) — count + distance
│ └── LargeWidgetGlanceDataType.kt # Radar (L) — full info
│
├── data/ # Persistence
│ ├── PreferencesRepository.kt # DataStore settings (singleton)
│ ├── models/ # PresetSettings, AlertSettings, ThreatLevel,
│ │ # WidgetState, BuiltInSoundSet, ScreenWakePolicy
│ └── database/ # Room database (ride statistics)
│
└── ui/ # Jetpack Compose
├── screens/ # DashboardScreen, SettingsScreen, OnboardingScreen
├── components/ # SettingsSection, SettingsSwitch, SettingsItem
└── theme/ # Dark theme, radar color palette
| Component | Version |
|---|---|
| Kotlin | 2.1.0 |
| Android Gradle Plugin | 8.7.3 |
| Jetpack Compose | BOM 2025.01.00 |
| Jetpack Glance | 1.1.1 |
| Karoo SDK | 1.1.7 |
| Room | 2.7.0 |
| DataStore | 1.1.2 |
| Target SDK | 35 |
| Min SDK | 26 |
./gradlew assembleDebug # Debug APK
./gradlew assembleRelease # Release APK (R8 minified + shrunk)
./gradlew test # Unit tests (JUnit 5)
./gradlew compileDebugKotlin # Fast compile checkTests use JUnit 5 with @DisplayName, @Nested, and @ParameterizedTest patterns. Assertions with Google Truth, mocking with MockK, coroutine testing with Turbine.
./gradlew testeiRadar does not collect, store, or transmit any personal data. Everything runs on-device. Full privacy policy.
MIT
