Smart Serow
Pi Zero 2W + Arduino Nano motorcycle info terminal.
Architecture
┌─────────────────┐ ┌─────────────────┐
│ Arduino Nano │──────│ Pi Zero 2W │
│ (sensors) │ UART │ (Flutter UI) │──── Display
└─────────────────┘ └─────────────────┘
- Pi Zero 2W: Runs Flutter UI via DRM/KMS (direct framebuffer, no X11)
- Arduino Nano: Sensor interface (future)
Project Structure
smart-serow/
├── arduino/ # Arduino sketches
│ └── hello.ino
├── pi/
│ └── ui/ # Flutter app (elinux target)
│ ├── lib/main.dart
│ ├── pubspec.yaml
│ └── elinux/ # Generated by flutter-elinux (gitignored)
├── scripts/
│ ├── build.sh # Cross-compile for ARM64
│ ├── deploy.sh # Push to Pi via rsync
│ ├── deploy_target.json
│ ├── pi_setup.sh # One-time Pi setup
│ └── smartserow-ui.service
├── pi_sysroot/ # Pi libraries for cross-linking (gitignored)
└── LICENSE # MIT
Build Environment Setup (WSL2)
Requirements
- WSL2 with Debian Trixie (glibc 2.38)
- flutter-elinux: https://github.com/aspect-apps/flutter-elinux
- ARM64 cross-compiler:
sudo apt install gcc-aarch64-linux-gnu g++-aarch64-linux-gnu binutils-aarch64-linux-gnu
Pi Sysroot (for cross-linking)
The ARM64 linker needs Pi's shared libraries to resolve symbols at link time. These don't execute locally - the linker just reads their symbol tables.
On the Pi, grab the libs:
tar czf pi_libs.tar.gz \
/lib/aarch64-linux-gnu \
/usr/lib/aarch64-linux-gnu
In WSL2, extract to project root:
mkdir -p pi_sysroot
tar xzf pi_libs.tar.gz -C pi_sysroot --strip-components=1
Key libraries needed:
- libxkbcommon, libEGL, libdrm, libgbm, libinput
- libudev, libsystemd, libfontconfig
Target Environment (Pi Zero 2W)
Requirements
- Debian Trixie (glibc 2.38 - must match build host!)
- Display connected via HDMI/DSI
First-Time Setup
# Copy scripts to Pi
scp scripts/pi_setup.sh scripts/smartserow-ui.service user@pi.local:~/
# Run setup on Pi
ssh user@pi.local
chmod +x pi_setup.sh
./pi_setup.sh
This installs:
- Runtime dependencies (libgl, libgles, libdrm, libgbm, libinput, fonts)
- Systemd service for auto-start
- User permissions for DRM/KMS access
Build & Deploy
Build (in WSL2)
./scripts/build.sh # Normal build
./scripts/build.sh --clean # Clean CMake cache first
Build output: pi/ui/build/elinux/arm64/release/bundle/
Deploy
Edit scripts/deploy_target.json:
{
"user": "mikkeli",
"host": "smartserow.local",
"remote_path": "/opt/smartserow",
"service_name": "smartserow-ui"
}
Deploy:
./scripts/deploy.sh # Just copy files
./scripts/deploy.sh --restart # Copy and restart service
Verify
ssh user@pi.local 'systemctl status smartserow-ui'
ssh user@pi.local 'journalctl -u smartserow-ui -f' # Live logs
Display Backends
Flutter-elinux supports multiple backends. We use GBM (DRM/KMS direct).
| Backend | Use Case | Notes |
|---|---|---|
gbm |
Production | Direct framebuffer, fast boot, no X11 |
x11 |
Debug | Needs X server, mouse/keyboard friendly |
wayland |
- | Requires compositor, more dependencies |
The backend is compiled in (we build with --target-backend-type=gbm).
The -b flag is for bundle path, not backend selection.
For X11 debugging, you'd need to rebuild with --target-backend-type=x11.
Known Issues / Gotchas
glibc version mismatch
Build host and Pi must have matching glibc. We use Debian Trixie on both.
Symptom: GLIBC_2.xx not found at runtime.
CMake caches compiler
If you change cross-compiler settings, run ./scripts/build.sh --clean.
flutter-elinux generates all platforms
The flutter-elinux create command scaffolds android/ios/web/etc.
These are gitignored - we only need elinux/ and linux/.
Libs not found at runtime
If libflutter_engine.so not found, check LD_LIBRARY_PATH in the service file.
Should point to /opt/smartserow/bundle/lib.
Development Tips
Local testing (Linux desktop)
cd pi/ui
flutter-elinux run -d linux
Check what a binary needs
# On Pi
ldd /opt/smartserow/bundle/smartserow_ui
Pi service management
sudo systemctl start smartserow-ui
sudo systemctl stop smartserow-ui
sudo systemctl restart smartserow-ui
journalctl -u smartserow-ui -f