Sachinthra N V
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Project Rover: From Raspberry Pi to ESP32

How I built a 4WD robotics platform with ESP32, solved brownout resets with proper power design, and created a remote PlatformIO flashing workflow.

RoboticsESP32Raspberry PiEmbedded SystemsPlatformIOIoT

Project Rover started as a Raspberry Pi-controlled 4WD platform and evolved into a real-time ESP32-based robot. This build taught me practical lessons in power distribution, firmware workflows, and responsive embedded web control.

In this post, I cover the hardware choices, the star-grounding approach that kept the system stable, the headless remote flashing pipeline, and the software architecture behind the control interface.

Hardware Bill of Materials

  • Microcontroller (Brain): ESP32-WROOM-32 (38-pin DevKitC)
  • Compile/Flash Host: Raspberry Pi 4 (Debian 12)
  • Motor Drivers: 2x L298N dual H-bridge modules
  • Motors: 4x 6V BO DC motors (100 RPM / 300 RPM variants)
  • Battery: 11.1V 2200mAh 3S LiPo (XT60)
  • Regulation: LM2596 3A buck converter

Phase 1: Power Distribution and Stability

With a 3S LiPo, voltage and current spikes are the biggest risk. A fully charged pack can hit around 12.6V, and motor stall current can introduce enough noise to crash the controller if wiring is sloppy.

Star Ground Topology

Instead of daisy-chaining grounds, I used a star topology:

  • Battery positive and ground go to central distribution points.
  • Raw battery voltage goes directly to both L298N motor driver inputs.
  • A separate branch feeds the LM2596, tuned to a stable 5.0V output.
  • The ESP32 VIN is powered from this regulated 5V branch.
  • ESP32 ground returns directly to the central ground hub.

This keeps noisy motor return current out of the logic ground path and improved system reliability immediately.

Phase 2: Brain Transplant to ESP32

I initially controlled the rover from a Raspberry Pi using Python GPIO libraries, but moved control to ESP32 for better real-time behavior and cleaner C++ firmware architecture.

Headless Flashing Workflow

I turned the Raspberry Pi into a remote compile-and-flash station so I could update firmware over SSH without tethering a laptop to the rover.

  • ESP32 connects to the Pi via a Micro-USB data cable.
  • I SSH into the Pi and run PlatformIO CLI.
  • pio run -t upload compiles and flashes firmware over USB.

One practical issue: if PlatformIO reports Unable to verify flash chip connection, the upload baud rate is usually too high. Setting upload_speed = 115200 in platformio.ini fixed this reliably.

Phase 3: Async Web Control and Motor Logic

With ESP32 in control, I built a responsive Wi-Fi control interface around ESPAsyncWebServer.

  • Web UI storage: HTML/CSS/JS served from LittleFS.
  • PWM control: Native ledc channels (8-bit, 1000Hz) drive ENA/ENB pins.
  • Motor safety: PWM duty limited to 50% to protect 6V motors from 3S battery voltage.

Fixing Brownout Resets

During early testing, pressing forward caused full reboots after a short burst.

  • Cause: simultaneous motor startup produced a current spike and voltage dip.
  • Fix: software soft-start ramped PWM from 0% to 50% over a few hundred milliseconds.

I also plan to add bulk capacitance near the LM2596 output as an additional hardware safeguard.

Phase 4: Sensor Expansion Roadmap

The 38-pin ESP32 board still leaves enough GPIO for autonomy features:

  • Ultrasonic radar (HC-SR04 + servo): obstacle scanning with a 5V-to-3.3V divider on Echo.
  • IR line tracking: digital reads on input-only GPIOs (34, 35, 36, 39).
  • I2C display: reserved GPIO 21 (SDA) and GPIO 22 (SCL) for telemetry.

Next milestone is integrating autonomous navigation and adding Bluetooth gamepad control.

Built with C++, PlatformIO, and many hardware debugging sessions.