Pull into your garage and it opens itself — triggered from your car's screen, no phone fumbling, no cloud, no subscription.
| Idle | Sending | Opened |
|---|---|---|
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Tap once to send. The screen shows a spinner while the BLE round-trip runs (typically <1s) and a confirmation when the door receives the open command. Failures show a "Try Again" button instead of auto-resetting, so you don't have to scramble to react while driving.
| Main (idle) | Sending | Pairing scan | Settings |
|---|---|---|---|
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The phone app mirrors the in-car flow but is the primary surface for setup. The hero open button doubles as a status indicator — concentric pulses while sending, fills green on success, fills pastel red on failure. The pairing screen runs a real BLE scan with a sweeping radar visual; tap the device that appears in the bottom sheet to pair it. Settings is grouped by Security / Testing / (Danger zone, when paired).
The watch companion app brings the same open button directly to your wrist. Tap once from the watch — it sends the open command to the phone over the Wear OS data layer, the phone handles the BLE round-trip, and the result comes back to the watch with a confirmation animation and haptic feedback. The watch screen turns on and shows the result even from lock screen. A watch tile is also available for one-tap access from the watch face without opening the app.
This project exists for a specific situation: you use a shared or communal garage — a car park in an apartment block, a rented space, a co-owned facility — where you have no access to the motor or the gate controller. You can't wire into the existing system, you can't install a proper smart opener, and the management won't let you touch anything. All you have is a key fob.
This gives you a hands-free way to open the door from your car's Android Auto screen without touching your phone. It works entirely over Bluetooth — no internet, no cloud, no subscription, no hub. The ESP32 presses the fob button for you when you tap the screen — either riding in the car itself powered off the car's USB / 12V socket (recommended for a single car / single user), or fixed near the entrance powered by a USB charger or battery (better for shared garages with multiple users or multiple vehicles). See Two ways to deploy for the trade-offs.
There are three ways to do the actual button-press. The recommended option (relay module) is beginner-friendly and works for most setups. Options B and C require no soldering inside the fob — important if you have to give it back when you move out. See Choose your trigger mechanism below.
It is not a replacement for a proper smart garage opener — if you own the garage and have access to the motor, there are better, cleaner solutions. This is specifically for the case where you have no choice but to use the fob.
In the car (recommended for a single car / single user): ESP32 + fob both ride in the car, powered off the car's USB or 12V socket via a USB-A adapter. The car's display becomes a permanent "open garage" button — tap once and the fob inside the glovebox triggers the gate. This is the smoothest experience: BLE always works because the ESP32 is in the same vehicle as your phone; the only range that matters is the fob's RF range to the gate motor from inside the car (typically 50–100 m, usually more than enough). No connectivity concerns, no power planning, no outdoor enclosure — the whole unit travels with the car and charges whenever the car is on. The in-car auto-fire (triggers automatically when the app detects the ESP32 in range on the AA screen) is particularly effective here.
At the garage (better for multi-user / multi-vehicle setups): ESP32 lives near the gate, powered by a wall outlet / power bank / solar, and is hidden in or near the entrance. The fob stays at the garage. This is the only deployment that supports multiple users or multiple vehicles — anyone you share the password with (other family members, housemates, visiting friends with their own car) can install the app on their own phone and open the same gate without you having to be there or hand anything over. The trade-off: you're now relying on BLE range from a phone in the car to a fixed point near the gate entrance (typically 10–30 m with walls; plan your placement accordingly). The firmware is optimized for this mode (low-power deep sleep, wake-on-BLE-advertising).
How it works: An ESP32 sits at the garage and is connected to a fob trigger mechanism (see the three options below). The Android app sends a BLE command from your phone directly to the ESP32, which then triggers the fob — exactly as if someone had pressed the button. No internet, no cloud, no Wi-Fi required.
There is no pre-built firmware — the PIN must be yours, so you build it yourself. It's one step:
- Connect your ESP32 via USB.
- Download
GarageAAtoESP32-flash-tool.zipfrom the Releases page, extract it, and run the script for your OS:- Windows: double-click
flash.bat - Linux:
chmod +x flash.sh && ./flash.sh
- Windows: double-click
The tool installs PlatformIO if needed, lets you pick your board, detects the port, asks for your PIN, compiles, and flashes. Your PIN is never saved to disk.
See docs/provisioning.md for full flashing instructions and troubleshooting.
- Play Store (easiest, includes Android Auto): Get it on Google Play
- APK (no Play Store): download the latest
.apkfrom the Releases page and sideload it. Note: sideloaded APKs do not work with Android Auto — AA only loads apps installed through the Play Store. - Build from source: open
android/in Android Studio, connect your phone via USB with debugging enabled, and click Run. Same limitation as the APK — Android Auto requires a Play Store install.
Wear OS companion (optional): if you have a paired Wear OS watch, install the companion from the Play Store — it is delivered automatically when you install the phone app. The watch app lets you open the garage directly from your wrist, with result feedback and haptics. A watch tile is also available for one-tap access from the watch face.
Open Garage Opener — it will walk you through scanning for your ESP32 and entering your PIN on first launch.
Connect your phone to Android Auto. Open Garage Opener and tap Open Garage.
Optional — geofence auto-open: in the phone app, go to Settings → (device) → Auto-open, set that device's garage location on the map, adjust the trigger radius (15–75 m), and enable the toggle. From then on the garage opens automatically when you approach — no tap, no phone interaction needed. Works with or without Android Auto: if AA is connected it fires via the car screen; otherwise it falls back to speed and activity detection. A dual-geofence system is used — an outer GPS warmup ring (configurable, default 400 m beyond the inner radius) starts requesting location fixes as you approach, so fresh speed data is ready when the inner zone fires. A notification is posted when the open fires so you always know it happened. See docs/geofence-auto-open.md for the full trigger logic.
Open history: the app keeps a persistent log of every open event — timestamp, trigger source (manual tap, Android Auto, geofence, voice), and result. Access it via the history entry on the main screen. Each row expands to show gate detail and suppression reason for geofence events.
Multiple openers: pair more than one device — any mix of BLE ESP32s and webhooks — instead of one replacing the last. Once 2+ devices are paired, every screen (phone, Android Auto, Wear tile, watch app, Quick Settings tile) gains a device picker so you choose which opener a tap fires. If you've set up a geofence per device, standing inside one (or more) of them auto-selects the matching device(s) everywhere, so multi-opener setups still feel like a single tap — see docs/geofence-auto-open.md for the full resolution logic.
ESP32 web log server (optional, enabled during flash): when enabled, the ESP32 hosts its own open Wi-Fi AP ({device-name}_{MAC}) with a captive portal. Connect any phone or laptop to it and a browser page opens automatically showing the full event log — timestamps, trigger sources, phone model, and any failed auth attempts. Useful for at-garage deployments where multiple people use the same opener. Enable it by answering y to the web log prompt in the flash tool.
Already automated your garage through Home Assistant, ESPHome, or anything else that can accept an HTTP request? You don't need any of this project's hardware. The app has a second, mutually-exclusive pairing mode: instead of scanning for an ESP32 over BLE, point it at a webhook URL.
- Every trigger source works exactly the same — manual tap, Android Auto, the watch tile, geofence auto-open, voice — the app just calls your webhook instead of a BLE device.
- Works out of the box with Home Assistant's native webhook trigger (
Settings → Automations → Webhook) — paste the URL, no token needed, since thewebhook_idin the URL is itself the secret. - If your endpoint expects an
Authorization: Bearer <token>header (for example, this project's own Home Assistant firmware integration), an optional token field is available under Advanced. - To set it up: on first launch, choose "I already have a webhook / Home Assistant automation" instead of scanning for a device. You can switch to this mode later from Settings as well.
- If you're pointing the app at this project's own ESP32 webhook, stick with the
.local(mDNS) hostname unless you've reserved the ESP32's IP on your router (DHCP reservation/static lease) — a plain IP can get reassigned to a different device after a lease renewal or reboot, silently breaking or misdirecting the webhook. Only switch to the IP (e.g.http://192.168.1.50/openinstead ofhttp://device-name.local/open) once that reservation is in place; it shaves roughly 1–3 seconds of mDNS resolution off every open, same token, same endpoint.
This is entirely an app-side feature — no firmware or flash tool changes required, and it works with any HTTP endpoint, not just Home Assistant.
This is also the best option if you're deploying this project's own ESP32 at home (wall-powered, on your home WiFi) rather than in a shared/communal garage. At home you have internet and can wire your ESP32's own HA webhook mode (see Home Assistant integration below) into an HA automation — HA fires the webhook, the ESP32 triggers the relay with full local RF range to the fob, and you get proper delivery confirmation through HA's own automation logs. This is different from the primary shared-garage use case this project targets, where there typically is no WiFi/internet available at all and BLE-direct is the only option — see Two ways to deploy above.
The ESP32 supports three ways to press the fob's button. Pick the one that fits your situation; the firmware handles all three from a single config flag (TRIGGER_MODE in firmware/include/config.h).
| Option | Soldering required? | Fob modified? | Best for |
|---|---|---|---|
| A — Relay module (recommended) | Yes (2 wires to fob button pads) | Yes | Anyone who can solder — beginner-friendly, reliable, galvanically isolated |
| B — Relay + power-rail switching | Minimal (copper tape only, outside fob) | No | Rented fob that must be returned untouched. Fully reversible. |
| C — Transistor | Yes (2 wires inside the fob) | Yes | Advanced — lower power draw than relay (~20 mA vs ~70 mA) |
Connect a small relay module between the ESP32 and the fob's button pads. The relay shorts the two pads when triggered — identical to pressing the button. No knowledge of transistor biasing needed; the relay module's onboard driver handles everything.
Use a 3V coil relay (e.g. Songle SRD-03VDC-SL-C) — works directly with the ESP32's 3.3V GPIO and power rail. A 5V coil relay also works if you power VCC from the board's 5V/VIN pin.
Wire: ESP32 GND → relay GND, ESP32 3.3V → relay VCC, ESP32 GPIO 26 → relay IN. Fob button pad A → relay COM, fob button pad B → relay NO.
This is also the right approach for power-rail switching (Option D in older docs): instead of shorting the button pads, connect COM/NO in series with the fob's battery ground rail — the fob has its button held down mechanically and fires every time it gets power. Renter-friendly, no fob modification required.
A single NPN transistor (2N2222, BC547, etc.) shorts the fob's two button pads. Lowest power draw (~20 mA vs ~60–80 mA for relay coil), but requires understanding transistor biasing and a 1 kΩ base resistor. Suitable if power budget is critical or you already have transistors on hand.
See docs/wiring_diagram.md for full diagrams, materials lists, and tuning notes for all options.
- ESP32-C3 development board — e.g., ESP32-C3 SuperMini, XIAO ESP32C3, ESP32-C3-DevKitM-1 (default build target) (must be an ESP32 variant with BLE — the ESP8266 has no Bluetooth. Other ESP32 variants such as the classic ESP32-DevKitC also work; see docs/advanced.md for instructions.)
- Trigger mechanism — pick one based on the table above:
- Option A (recommended): relay module with 3V coil, e.g. Songle SRD-03VDC-SL-C (~$1–2) — works directly with ESP32 3.3V GPIO and power rail
- Option B: relay module (same as A) + copper tape (two ~20 mm discs) for fake battery contacts + thin wire — no soldering inside the fob
- Option C: NPN transistor (2N2222 / BC547 / 2N3904, ~$0.10) + 1 kΩ resistor
- Garage key fob — for Options A and C you'll solder two wires to the button pads inside it. For Option B you don't open the fob at all.
- Power source — pick one based on where you're deploying:
- Wall outlet + any USB phone charger (simplest — if there's a socket nearby at the garage)
- Solar power bank (self-sustaining, no maintenance — for at-garage deployments without a socket)
- USB power bank with always-on / low-current mode (~12 months per charge)
- 18650 LiPo cells + TP4056 charger board (DIY, most flexible)
- Car USB / 12V socket (for the in-car deployment — ESP32 + fob both stay in the car, powered whenever the car is on)
firmware/ ESP32 firmware (PlatformIO + Arduino framework)
android/app/ Phone app (Kotlin + Car App Library + Android Auto)
android/wear/ Wear OS companion app (Compose for Wear OS)
docs/ Wiring diagram, power budget, provisioning guide
- The PIN never travels over the air — only an HMAC-SHA256 hash of a fresh random nonce.
- Each connection uses a new nonce, so replay attacks are impossible.
- See docs/provisioning.md for details.
Three options:
- A — Relay module (recommended) — beginner-friendly, galvanically isolated, requires soldering to fob button pads
- B — Relay + power-rail switching — no soldering inside the fob, fully reversible, best for rented fobs
- C — Transistor — lowest power draw (~20 mA), requires soldering, advanced
See docs/wiring_diagram.md for full diagrams, materials lists, and component notes.
See docs/power_budget.md for battery sizing and solar guidance.
Test the Android Auto UI without an ESP32: Enable Demo mode in the app's phone Settings. Tapping "Open Garage" on the AA screen will run the full UI flow (connecting → opened) and show a toast on your phone — no BLE or hardware needed. Use this with the Android Auto Desktop Head Unit to test entirely on your PC.
Test the firmware without the Android app: Use nRF Connect (free on Android/iOS) to talk directly to the ESP32 and verify auth works. See docs/provisioning.md for the full verification steps.
For building on non-C3 boards and other advanced topics see docs/advanced.md.
This project is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International.
You can: build your own unit, share it, modify it, publish derivatives. You cannot: sell it, use it in a commercial product, or relicense it. You must: credit the original author and link back to this repository.
See LICENSE for full terms.