Package Your Driver

Learning Goals 5 min

Cluster H's capstone: take one of your Cluster A-G sensor / motor wrappers and turn it into a polished, distributable Arduino library. By the end of this lesson you will:

1. Pick a wrapper worth packaging (SmoothedSensor, Motor class, RangeFinder, etc.).
2. Refactor into a proper library structure with API polish (defaults, doxygen, const-correctness).
3. Optionally publish to GitHub and submit to the Library Registry.

Warm-Up 10 min

Look back at your reusable code so far:

• Motor (L03-08, L03-41) — wraps L298N IN1/IN2/EN signals into setSpeed(int).
• SmoothedSensor (L03-41) — analog sensor with running-average smoothing.
• RangeFinder (L03-43) — HC-SR04 wrapper returning cm.
• PID (L04-24) — generic PID controller.
• Blinker (L03-42, L04-41) — non-blocking blink.
• ShiftReg (L03-21) — 74HC595 helper.

Pick one. Today we polish it end-to-end and (optionally) ship.

New Concept · From wrapper to library 25 min

The polish pass

1. Split into .h + .cpp (or .h only if header-only is fine).
2. Apply API design principles from L04-42: defaults, const, doxygen, private internals.
3. Add 2-3 examples showing common uses.
4. Write README with quick start.
5. Test on multiple boards: UNO, Nano, ESP32. Use #ifdef for board differences.
6. Version it 0.1.0 until you're confident → 1.0.0 when stable.
7. License: pick MIT or similar.
8. Optionally publish via the L04-43 flow.

Example: turn Motor into a library

Start with the L03-09 Motor struct + functions. Convert to a class library.

Motor.h

#ifndef MOTOR_H
#define MOTOR_H

#include <Arduino.h>

/**
 * @brief L298N-driven DC motor with signed PWM speed.
 *
 * Each instance handles one motor channel of an L298N H-bridge.
 * Connect IN1, IN2, and ENA (or IN3/IN4/ENB) to digital pins.
 * Positive duty = forward; negative = reverse; zero = brake.
 */
class Motor {
public:
  /**
   * @param in1 Direction pin 1.
   * @param in2 Direction pin 2.
   * @param en  PWM-capable enable pin.
   */
  Motor(int in1, int in2, int en);

  /// Configure pins as OUTPUT. Call in setup().
  void begin();

  /// Set signed duty cycle: -255..+255.
  void setSpeed(int duty);

  /// Stop with both IN pins LOW (active brake).
  void brake();

  /// Disconnect motor (coast). Requires PWM pin to support 0.
  void coast();

  /// Last commanded signed duty.
  int getSpeed() const { return lastDuty_; }

private:
  int in1_, in2_, en_;
  int lastDuty_;
};

#endif

Motor.cpp

#include "Motor.h"

Motor::Motor(int in1, int in2, int en)
  : in1_(in1), in2_(in2), en_(en), lastDuty_(0) {}

void Motor::begin() {
  pinMode(in1_, OUTPUT);
  pinMode(in2_, OUTPUT);
  pinMode(en_,  OUTPUT);
  brake();
}

void Motor::setSpeed(int duty) {
  duty = constrain(duty, -255, 255);
  if (duty > 0) {
    digitalWrite(in1_, HIGH);
    digitalWrite(in2_, LOW);
    analogWrite(en_, duty);
  } else if (duty < 0) {
    digitalWrite(in1_, LOW);
    digitalWrite(in2_, HIGH);
    analogWrite(en_, -duty);
  } else {
    brake();
  }
  lastDuty_ = duty;
}

void Motor::brake() {
  digitalWrite(in1_, LOW);
  digitalWrite(in2_, LOW);
  analogWrite(en_, 0);
  lastDuty_ = 0;
}

void Motor::coast() {
  analogWrite(en_, 0);
  lastDuty_ = 0;
}

Example sketch

#include <Motor.h>

Motor leftWheel(4, 7, 5);
Motor rightWheel(8, 9, 6);

void setup() {
  leftWheel.begin();
  rightWheel.begin();
}

void loop() {
  leftWheel.setSpeed(200);
  rightWheel.setSpeed(200);
  delay(2000);
  leftWheel.setSpeed(-200);
  rightWheel.setSpeed(-200);
  delay(2000);
}

Cross-board support

void Motor::setSpeed(int duty) {
  // ...
#if defined(ESP32) || defined(ESP8266)
  // ESP boards use a different PWM resolution by default (10-bit)
  duty = (duty * 1023) / 255;
#endif
  // ...
}

Or call analogWriteResolution(8) in begin() to standardise.

Worked Example · Ship one of your libraries 30 min

Pick

Pick the most polished of your wrappers. SmoothedSensor is a great choice — small, useful, no hardware-specific.

Refactor

Apply all of L04-42's principles. Split files. Add defaults. Add doxygen. Add 2 examples.

Test

Compile + run on UNO. Compile + run on ESP. Note any divergence; fix or document.

Document

README with quickstart. License. Optional: HTML docs from Doxygen.

Publish (optional)

Push to GitHub. Tag 1.0.0. Submit PR to Library Registry.

Celebrate

If you submitted: your code is now installable by anyone in the world. Real software shipping.

Cluster H done. Final cluster (exam prep) starts tomorrow.

Try It Yourself 15 min

Mini-Challenge · Portfolio piece 10 min

Take one polished library you've built. Use it in a different sketch that solves a real problem. Take a video / write-up describing:

1. What problem does the library solve?
2. Quick usage example.
3. What you'd add for v2.

This is a portfolio piece for engineering applications and showcases real authorship.

Recap 5 min

Library = struct/class wrapper + polished API + examples + README + license + Git tag + PR to registry. Once shipped, others install with one click. Cluster H done. Final cluster: Arduino Certification Exam preparation.

Driver library

A reusable wrapper for a hardware component (sensor, motor, display). Hides protocol / wiring details behind a clean API.

Polish pass

The conversion from "works in my sketch" to "ready for everyone's sketches": defaults, docs, examples, license.

Header-only library

Library with everything in .h files (no .cpp). Simpler for small utilities; means definitions inline.

Multi-architecture support

Library that works on UNO, ESP, Nano 33 BLE. Use #ifdef for board-specific bits.

Portfolio piece

A published project you can show to others — university applications, internships, engineering portfolios. Open source libraries are excellent portfolio fodder.

Homework 5 min

1. Polish one library. Optionally publish.
2. Read ahead to ARD-L04-45 (Exam Format and Domains). Cluster I — final stretch.