Base Station¶

Standalone ground control station. Separate Raspberry Pi powered by its own wall adapter (5V USB). Not wired into either the GEO-DUDe or gimbal power systems.

Hardware¶

Network Configuration¶

Ethernet (eth0) — Laptop Link¶

The Pi's built-in Ethernet port connects directly to the operator laptop via a USB Ethernet adapter or small unmanaged switch. The Pi keeps a static IP on eth0 and runs DHCP for connected laptops, so the laptop side should be left on automatic/DHCP.

On macOS, the USB adapter may appear under names like "USB 10/100/1000 LAN" or a custom renamed service. Leave it on Using DHCP. No manual IP assignment is required.

The reliable operator URL is:

http://192.168.50.2/

WiFi Hotspot (wlan0) — Subsystem Link¶

The Pi runs a WiFi hotspot on wlan0 at 192.168.4.1/24. GEO-DUDe Pi and ESP32 connect to this network.

SSH Access¶

ssh zeul@192.168.50.2

Communication Links¶

The base station Pi acts as the central coordinator. The operator controls the system from a laptop connected to the base station Pi over Ethernet, which relays commands to both the GEO-DUDe servicer (via its onboard Pi) and the gimbal apparatus (via ESP32) over WiFi.

graph LR
    LAPTOP["Laptop<br/>(Operator)<br/>DHCP on 192.168.50.x"] -->|Ethernet| BASEPI["Base Station Pi<br/>(Ground Control)<br/>eth0: 192.168.50.2<br/>wlan0: 192.168.4.1"]
    BASEPI -->|WiFi| GEOPI["GEO-DUDe Pi<br/>(Servicer)<br/>192.168.4.166"]
    BASEPI -->|WiFi| ESP["ESP32<br/>(Gimbal)<br/>192.168.4.x"]
    GEOPI -->|WiFi| ESP

Network Architecture¶

The base station Pi runs a WiFi hotspot (groundstation) that both the ESP32 and GEO-DUDe Pi connect to. The laptop connects to the Pi via Ethernet (192.168.50.0/24 subnet).

IP forwarding and NAT are enabled on the Pi so the laptop can reach WiFi clients:

sudo sysctl -w net.ipv4.ip_forward=1
sudo nft add table ip nat
sudo nft add chain ip nat postrouting { type nat hook postrouting priority 100 \; }
sudo nft add rule ip nat postrouting oifname wlan0 masquerade
sudo nft add table ip filter
sudo nft add chain ip filter forward { type filter hook forward priority 0 \; policy accept \; }

On the laptop, add a route to the WiFi subnet:

sudo route add -net 192.168.4.0/24 192.168.50.2

Notes¶

• No fusing or power distribution needed — just a Pi with a USB power supply
• WiFi range should be tested with the GEO-DUDe rotating inside the gimbal apparatus
• The GEO-DUDe Pi and ESP32 also communicate directly with each other over WiFi for coordinated operation
• Laptop connects via Ethernet to the Pi (192.168.50.0/24)

Software¶

GEO-DUDe Control Web UI (wheel-control.service)¶

Flask web app exposed to operators at http://192.168.50.2/. Internally the service still runs on port 8080, with port 80 redirected to it on the groundstation Pi. Controls GEO-DUDe hardware via HTTP to 192.168.4.166:5000. Source: zeulewan/geodude-control (private).

Camera:

• Live MJPEG preview from RPi Camera Module 3 (IMX708)
• 640x480 @ 10fps, JPEG quality 50 (bandwidth-limited by WiFi)
• 180° flipped, proxied through groundstation

System Stats:

• CPU%, temperature, load average for both Pis
• Polled at 0.5Hz

MACE (Reaction Wheel) panel:

• Hold-to-spin with configurable power and server-side ramp rate (0.1-100 %/s)
• Bidirectional ESC — center-stick control (1500us=stop, forward/reverse proportional)
• Ramp progress bar showing target vs current throttle
• No arming sequence needed (plug and play ESC)
• RPM display from encoder (computed server-side at 30Hz, 10-sample rolling average)
• RPM saturation limit at 600 RPM with hysteresis (coast at 600, resume at 420)
• 3-second watchdog — auto-stops motor if browser disconnects

Attitude Control panel:

• Closed-loop PID controller for body angle (runs on GEO-DUDe at 100Hz)
• Gyro gz integration for body angle estimation with bias calibration
• Angle dial (body angle + setpoint), revolution counter
• Nudge buttons (+10°, -10°, +90°, -90°) and direct setpoint input
• Live-adjustable PID gains (Kp, Ki, Kd) and max throttle ceiling
• Wheel saturation detection (600 RPM max, auto-coast when saturated)
• Rate-limited output (40.5%/s max)
• Deadband-skip mapping (PID output → bidirectional motor range, skipping ±50-75us center deadband)
• 5-second watchdog auto-disable
• Mutual exclusion with manual MACE control

PCA9685 Channels panel:

• Individual sliders for all servo channels (500-2500us for B/W/E/S, center 1500us)
• Servos always active at center on page load (continuous signal required)
• Per-channel center button, ALL CENTER button
• Slider thumb-drag only (no track click-jump), center button ramps slowly

Sensor readout:

• Live gyroscope, accelerometer, and encoder angle from GEO-DUDe IMU/encoder
• GEO-DUDe connection status and motor error reporting

Sensor Server (sensor-server.service on GEO-DUDe)¶

Flask API on GEO-DUDe (192.168.4.166:5000). Controls PCA9685 over I2C and reads IMU/encoder.

• GET /sensors — gyro, accel, encoder angle, RPM (30Hz I2C polling)
• GET /system — CPU%, temperature, load average
• POST /motor — MACE ESC control (pulse width in us, 1500=stop, >1500=forward, <1500=reverse, blocked when attitude controller active)
• POST /pwm — per-channel PCA9685 control ({"channel": "B1", "pw": 1500})
• POST /pwm/off — all channels off
• GET /channels — channel mapping
• GET /camera — MJPEG stream from RPi Camera Module 3

Attitude Controller (attitude-controller.service on GEO-DUDe)¶

Separate Flask API on GEO-DUDe (192.168.4.166:5001). PID control loop for body angle.

• GET /status — full controller state (body angle, setpoint, error, output, gains, RPM, saturation)
• POST /enable — calibrate gyro (2s), arm ESC (3s), start PID
• POST /disable — stop PID, coast motor
• POST /setpoint — set target body angle
• POST /nudge — adjust setpoint by delta
• POST /zero — reset body angle and setpoint to 0
• POST /gains — adjust PID gains live
• POST /calibrate — re-run gyro bias calibration
• POST /stop — emergency disable

Networking Notes¶

• Offline local network — no internet
• Ethernet clients get 192.168.50.x addresses automatically by DHCP from the groundstation Pi
• Use http://192.168.50.2/ for the UI; do not rely on hostname discovery for demos or field use
• WiFi bandwidth ~3 Mbps — camera stream and sensor polling are bandwidth-conscious
• GEO-DUDe SSID configured as groundstation (no space) in NetworkManager