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Hedy

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What do I need to learn to build a robot with Nucleo-F401RE?

#nucleof401re #robot #stm32 #sensors

The Nucleo-F401RE is perfect for a first “real” robot because it has ST-LINK built-in, plenty of timers for PWM + encoders, and Arduino-style headers for quick wiring.

Below is a practical “learn STM32 by building the robot” roadmap, with a solid hardware stack and the exact STM32 peripherals you’ll learn in the right order.

1) Pick a simple robot architecture (do this first)

Start with a 2-wheel differential drive (2 DC gear motors + 1 caster). It’s the easiest to control and debug.

Recommended BOM (robot base)

Core

  • Nucleo-F401RE
  • 2× DC gear motors (6–12V) + wheels
  • 1× motor driver board (dual H-bridge): TB6612FNG / DRV8833 / L298N (pick one)
  • Battery: 2S Li-ion/LiPo (7.4V) or 6×AA (simple)
  • 5V/3.3V regulation:
    • If using 2S battery: buck converter to 5V
    • Nucleo can be powered by 5V on VIN/5V pin (board then makes 3.3V)
  • Wires + breadboard or perfboard

Sensors (add in phases)

  • Wheel encoders (quadrature) highly recommended
  • IMU (I2C): e.g., MPU-6050/ICM-series (any common I2C IMU)
  • Distance sensor: ultrasonic (HC-SR04) or ToF (I2C)

Debug tools (huge time saver)

  • Cheap logic analyzer (for UART/I2C/SPI)
  • Multimeter

2) Power rules (most robot bugs are power bugs)

  • Never power motors from the Nucleo 5V pin.
  • Power path should be:
    • Battery → Motor driver (VM)
    • Battery → Buck → 5V → Nucleo (5V/VIN)
  • Common ground is mandatory: Battery GND = motor driver GND = Nucleo GND
  • Add a bulk capacitor near motor driver VM: 220–1000 µF helps with brownouts.

3) Learning path that maps directly to robot features
Phase A — “It moves” (1–2 days)

Goal: Drive both motors open-loop.
You learn:

  • GPIO output (direction pins)
  • Timer PWM (speed control)

Motor driver signals you’ll typically use:

  • AIN1/AIN2 + PWMA
  • BIN1/BIN2 + PWMB
  • STBY/EN (enable)

CubeMX setup

  • Enable 2 PWM channels (e.g., TIM3 CH1/CH2)
  • Configure 2–4 GPIOs for direction
  • Start PWM and vary duty cycle

Phase B — “It moves straight” (2–5 days)

Goal: Read encoders and do speed control so both wheels match.
You learn:

  • Timer Encoder Interface mode (best)
  • Interrupt basics (optional)
  • PID speed loop

Why encoders matter: without them, the robot drifts and turns randomly because motors aren’t identical.

Phase C — “It goes where you tell it” (1–2 weeks)

Goal: Drive distance/angle commands.
You learn:

  • Differential drive kinematics
  • Closed-loop control (speed + heading)
  • IMU via I2C (optional but great)

Phase D — “It navigates” (ongoing)

Add:

  • Obstacle avoidance (distance sensor)
  • Line following (IR array)
  • Remote control (Bluetooth UART)

4) Wiring example (typical dual H-bridge)

This is generic and works for TB6612/DRV8833-type drivers:

STM32 → Motor Driver

  • PWM_A → PWMA
  • PWM_B → PWMB
  • DIR_A1, DIR_A2 → AIN1, AIN2
  • DIR_B1, DIR_B2 → BIN1, BIN2
  • EN/STBY → STBY/EN
  • GND → GND (must share)

Power

  • Battery + → VM (motor supply)
  • Battery – → GND
  • Buck 5V → Nucleo 5V/VIN
  • Buck GND → common GND

Encoders → STM32

  • Left encoder A/B → TIMx CH1/CH2 (encoder mode)
  • Right encoder A/B → TIMy CH1/CH2
  • Use pull-ups if encoder outputs are open collector.

Tip: Nucleo-F401RE exposes many timer pins; choose pins that support PWM outputs and encoder channels, and confirm in the Nucleo pinout.

5) CubeIDE/CubeMX peripheral “shopping list” for this robot

You’ll end up using these a lot:

  • TIM PWM: 2 channels (left/right speed)
  • TIM Encoder: 2 timers (left/right wheel)
  • UART: debug prints + later Bluetooth control
  • I2C: IMU / ToF sensor
  • ADC: battery voltage monitoring
  • (Optional) FreeRTOS: only after you’re comfortable without it

6) A proven firmware structure (simple, robust)

Run a fixed-rate control loop (no RTOS needed at first):

  • 1 kHz (every 1 ms): read encoders, compute wheel speed
  • 100–200 Hz: PID speed control update
  • 20–50 Hz: navigation logic (distance/heading/obstacle)

A clean module split:

  • motor.c (set PWM + direction)
  • encoder.c (read counts, compute speed)
  • control.c (PID)
  • robot.c (drive commands: forward/turn)
  • comms.c (UART CLI)

7) Your first “robot milestone plan” (no guessing, just build)

  1. PWM one motor forward/backward
  2. PWM both motors, manual speed commands over UART
  3. Read both encoders reliably
  4. Implement wheel speed PID (robot drives straight)
  5. Implement “drive X cm” and “turn Y degrees”
  6. Add sensor-based stopping (distance sensor)
  7. Add Bluetooth control (UART) or a simple command protocol

8) Quick parts choice advice (so you don’t get stuck)

  • If your motors are small (≤1A each typical): TB6612FNG / DRV8833 class drivers are great.
  • If motors are bigger: pick a higher-current driver and plan real heat dissipation.
  • Get encoders early. They make the project way more predictable.

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