Mdd32-bot

MDD32 Bot

A minimal two-wheeled differential-drive robot built around an ESP32-S3. The project includes the custom PCB, the 3D-printable chassis, and the firmware (packaged as an Arduino library).

The MDD32 board is a small, battery-powered controller for two-wheeled robots. It pairs an ESP32-S3 module with a dual H-bridge motor driver and connectors for two N20 gear motors with quadrature encoders. A single-cell Li-ion/LiPo battery powers the board, and it charges over USB-C. The same USB-C port is used for programming and serial debugging through the ESP32-S3's native USB.

Repository Layout

Board Features

• ESP32-S3-MINI-1-N8 module with Wi-Fi and Bluetooth LE
• Native USB-C for programming, serial, and charging; no USB-UART bridge needed
• Single-cell Li-ion/LiPo charging with power-path management (TI BQ24072)
• 5 V boost converter for the motor supply (TI TPS61023)
• 3.3 V LDO for the logic supply (Diodes AP2114H-3.3)
• Dual H-bridge motor driver with per-channel current limiting (TI DRV8833)
• Two 6-pin JST-SH motor ports for N20 encoder motors
• Battery voltage sensing that only draws current while the board is switched on
• Charge and USB-power status, shown on LEDs and readable by the ESP32
• Slide power switch, plus RESET and BOOT buttons
• 4-layer, 62 × 28 mm PCB with four M2.5 mounting holes

Hardware

Power

• Charger: the BQ24072's input current limit is set to about 1.4 A (R9 = 1.1 kΩ) and its fast-charge current to about 330 mA (R10 = 2.7 kΩ). Size your battery for this charge rate, or change R10.
• Motor current limit: each DRV8833 channel limits at about 0.67 A (300 mΩ sense resistors).

ESP32-S3 Pin Map

Connectors

Opening the PCB

1. Open hardware/MDD32_Bot/MDD32_Bot.kicad_pro in KiCad 10 or newer.
2. The project's symbol, footprint, and 3D model libraries are referenced relative to the project folder, so no extra library setup is needed.
3. Each component in the schematic has an LCSC part number in its LCSC field for JLCPCB assembly. The Fabrication Toolkit plugin can generate the Gerbers, BOM, and placement file in one step.

Firmware

The firmware lives in firmware/MDD32_Bot/, structured as an Arduino library with no external dependencies:

Installing

Copy or symlink firmware/MDD32_Bot into your Arduino libraries folder (for example ~/Documents/Arduino/libraries/MDD32_Bot), and install the esp32 by Espressif Systems board package.

Board settings

In the Arduino IDE, select ESP32S3 Dev Module and set:

• USB CDC On Boot: Enabled (required for Serial output over the native USB port)
• Flash Size: 8MB
• PSRAM: Disabled

The ESP32-S3 is programmed over USB-C. If the port doesn't appear, hold BOOT, press and release RESET, then release BOOT to enter the bootloader.

Firmware API

Include the library and create a single MDD32_Bot instance. It exposes two subsystems as public members: battery and drive.

#include <MDD32_Bot.h>

MDD32_Bot bot;

void setup() {
    Serial.begin(115200);
    if (!bot.begin()) {
        Serial.println("MDD32 Bot init failed");
        while (1);
    }
    bot.drive.straight(6.0f);   // drive forward at 6 cm/s
}

void loop() {
    bot.drive.update();         // must be called frequently for PID control
}

MDD32_Bot

MDD32_Battery

MDD32_Drive

Differential drive with per-wheel PID speed control, acceleration ramping, and wheel-sync correction. Call update() frequently from loop() to run the control loop.

DriveTelemetry contains: leftRPM, leftPWM, rightRPM, rightPWM, leftCount, and rightCount (wheel-output RPM, applied PWM, and raw encoder counts).

Tuning overrides

The control parameters default to the values in src/definitions/robot_definitions.h. These setters override them at runtime; call them after bot.begin(). The sketches in examples/Tuning/ use them so you can tune without editing the library.

License

This project, including the firmware, PCB design files, and mechanical/3D-printed parts, is licensed under the MIT License.