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🏎️ Heavy-Duty Drive: Pico & HC-06 DC Motor Controller

A high-current motor control architecture engineered for high-torque Inductive Loads (Automotive Wiper Motors). This system bridges a custom Android UI with the RP2040 PWM engine for robust wireless mobile robotics.

MIT App Inventor Bluetooth Interface

🚀 Engineering Backstory: Torque vs. Control

Standard hobby-grade motor drivers are insufficient for the current inrush required by 12V automotive wiper motors. This project focuses on managing the Power Electronics required for heavy-duty chassis, using the Raspberry Pi Pico to provide the precision timing needed for smooth acceleration curves.

By utilizing the HC-06 Bluetooth Transceiver as a transparent UART bridge, the system achieves a 10-meter wireless control radius without the overhead of Wi-Fi or complex network stacks.

✨ Key Technical Features

  • Hardware-Timed PWM: Utilizes the RP2040’s dedicated PWM slices to ensure jitter-free motor speed control independent of CPU load.
  • Transparent UART Bridge: Low-latency 3.3V TTL communication between the Pico and the HC-06 Bluetooth module.
  • Non-Blocking Parsing: Firmware architecture allows for real-time command processing (Forward, Reverse, Pivot) without stalling the control loop.
  • Inductive Load Protection: Designed for use with heavy-duty H-Bridges capable of handling high back-EMF and stall currents.
  • Control Theory Ready: Includes a modular framework for PID ($K_p, K_i, K_d$) implementation, ready for encoder or IMU feedback.

🛠️ Hardware Stack

  • MCU: Raspberry Pi Pico (RP2040).
  • Communication: HC-06 Bluetooth (Serial Port Profile).
  • Power Stage: 43A BTS7960 (or similar) High-Current H-Bridge.
  • Actuators: 2x 12V DC Brushed Wiper Motors.
  • Control Layer: MIT App Inventor (Android) & MicroPython.

📐 Logic & Signal Flow

UART-to-PWM Conversion

The system operates on an Interrupt-Driven Command Logic:

  1. Packet Capture: The HC-06 receives RF signals and pushes ASCII characters to the Pico's UART0 RX buffer.
  2. Logic Branching: The MicroPython script evaluates the character (e.g., 'F' = $1111_2$, 'S' = $0000_2$) to determine the H-Bridge pin states.
  3. Duty Cycle Modulation: The Pico updates the PWM.duty_u16() registers to translate user input into physical velocity.

Closed-Loop Potential

While this version operates in Open-Loop, the internal architecture is built for Proportional-Integral-Derivative control. Placeholders for $K_p, K_i,$ and $K_d$ constants are integrated into the global scope to support future quadrature encoder feedback for synchronized wheel velocity.

📱 The Controller App (MIT App Inventor)

The interface is a dedicated control node:

  1. Directional Matrix: Maps touch-events to specific UART characters.
  2. Link Monitoring: Real-time visual feedback on the Bluetooth SPP status.
  3. Parameter Injection: UI infrastructure designed to pass dynamic PID constants to the Pico's volatile memory for live tuning.

© 2026 MatsRobot | Licensed under the MIT License