Create Custom Arduino Library

Help the user interface with Arduino sensors or peripherals from MATLAB by creating a custom arduino library that bridges MATLAB and Arduino C++ code.

When to Use

• User wants to read sensors not natively supported (DHT11, DHT22, IMU, air quality)
• User wants to control peripherals not natively supported (OLED displays, motor drivers, NeoPixels)
• User asks "How do I use [sensor/actuator/peripheral] from MATLAB with Arduino?"
• User wants to wrap an existing Arduino C++ library for MATLAB access
• User mentions LibraryBase, arduinoioaddons, or custom addon creation

When NOT to Use

• Peripheral is already supported natively (use listArduinoLibraries to check)
• User needs to discover or connect to an Arduino board (see matlab-connect-arduino)
• User wants generic I2C/SPI communication (built-in)
• User wants to deploy standalone Arduino code (no MATLAB connection)
• User wants Simulink Arduino deployment (different workflow)
• User wants to fix Arduino hardware setup screens

Workflow

MANDATORY GATE — do not skip, but keep it fast:

Before creating a custom addon, you MUST run Steps 0 and 1 below. These are quick checks (one MATLAB command + one sentence about File Exchange), not deep research. Report findings in 1-2 lines and move on. If native support or a community addon exists, stop. Otherwise proceed to Step 2 immediately.

STEP 0: Check Native Support (ALWAYS DO FIRST)

listArduinoLibraries

If the peripheral is in the list, tell the user and STOP. Do NOT proceed to Step 2 or beyond. Do NOT generate custom library code. Common built-in: I2C, SPI, Serial, Servo, RotaryEncoder, Ultrasonic, ShiftRegister

STEP 1: Search File Exchange (MathWorks contributions only)

Search for existing add-ons contributed by the MathWorks MATLAB Hardware Team:

• Search: site:mathworks.com/matlabcentral/fileexchange Arduino <peripheral>
• Look for packages with +arduinoioaddons folder structure
• Only use results authored by MathWorks — filter by author "MathWorks Hardware Team" or "MathWorks". Do NOT recommend community contributions from unknown third parties.

If a MathWorks-contributed add-on is found, guide the user through installation:

1. Download/extract the addon package
2. addpath the folder containing +arduinoioaddons
3. Install third-party Arduino libraries via arduinoio.customLibrary.downloadLibrary
4. Verify with listArduinoLibraries

STOP here if a MathWorks add-on is found — do NOT proceed to Step 2 or beyond.

STEP 2: Gather Required Inputs

Before creating a custom library, the user MUST provide:

1. Custom library name (e.g., MyDHT22)
2. Third-party Arduino library name (if wrapping one; e.g., DHT22, U8g2)
3. Target output directory for the MATLAB add-on files

Do NOT proceed to any further steps until all required inputs are provided. If any are missing, ask the user explicitly and wait for their response.

STEP 3: Install Third-Party Arduino Library

% R2025a+ — use downloadLibrary (preferred)
arduinoio.customLibrary.downloadLibrary("<ArduinoLibraryName>")

% Accepts: library name, name@version, GitHub URL, or local .zip path
% Examples:
arduinoio.customLibrary.downloadLibrary("DHT22")
arduinoio.customLibrary.downloadLibrary("U8g2")
arduinoio.customLibrary.downloadLibrary("https://github.com/olikraus/u8g2")

Verify installation:

dir(fullfile(arduinoio.CLIRoot, 'user', 'libraries'))

For R2024a-R2024b (no downloadLibrary): manually extract the library zip into fullfile(arduinoio.CLIRoot, 'user', 'libraries', '<LibName>').

For pre-R2024a (no CLIRoot): use arduinoio.IDERoot instead of arduinoio.CLIRoot.

STEP 4: Scaffold the Add-On

% R2025a+ — use createLibraryTemplate (preferred)
arduinoio.customLibrary.createLibraryTemplate("<CustomLibraryName>")

This creates the folder structure in the current working directory (pwd) and adds the path automatically. After calling it, the generated files are at:

<pwd>/+arduinoioaddons/+<CustomLibraryName>Folder/<CustomLibraryName>.m
<pwd>/+arduinoioaddons/+<CustomLibraryName>Folder/src/<CustomLibraryName>.h

Do NOT search other locations — the files are always in pwd.

Naming: createLibraryTemplate("X") creates +XFolder/X.m — it appends "Folder" to the package name automatically. The generated setup() has placeholder comments — clear the body (no .begin() calls). The generated loop() is unused and can be deleted.

For pre-R2025a: create the folder structure manually:

<targetDir>/+arduinoioaddons/+<FolderName>/<ClassName>.m
<targetDir>/+arduinoioaddons/+<FolderName>/src/<HeaderName>.h

Then register:

addpath('<targetDir>');
savepath;

STEP 5: Configure the MATLAB Class

Update the generated .m file. See "MATLAB Class Property Rules" below for exact values.

Add minimal comments to the generated .m file for user understanding:

• A file-level comment block stating the class purpose and the peripheral it wraps
• Brief comments on non-obvious property values (e.g., why DependentLibraries is empty)
• A one-line comment above each public method explaining what it does

STEP 6: Write the C++ Header

Update the generated .h file. See "C++ Header Rules" below and read references/cpp-patterns.md for templates.

Add minimal comments to the generated .h file for user understanding:

• A file-level comment stating the addon name and peripheral it supports
• A one-line comment above each command ID #define explaining the command
• A brief comment in commandHandler for each case describing what it does

STEP 7: Verify

listArduinoLibraries  % Must show your library name
a = arduino("<port>", "<board>", "Libraries", "<FolderName>/<ClassName>");
obj = addon(a, "<FolderName>/<ClassName>", <args>);

MATLAB Class Property Rules

Property	Format	Example	Notes
LibraryName	'FolderName/ClassName'	'Adafruit/DHT22'	Must match namespace
DependentLibraries	Cell of MATLAB addon names	{} or {'I2C'}	See decision table below
LibraryHeaderFiles	'<ArduinoLibFolder>/<header.h>'	'DHT/DHT.h'	Folder name in CLIRoot + header filename
CppHeaderFile	fullfile(arduinoio.FilePath(mfilename('fullpath')), 'src', '<Name>.h')	—	Always this pattern
CppClassName	Must match C++ class name	'DHT22Base'	Exact match required

DependentLibraries Decision Table

Scenario	Value	Reason
GPIO-only peripheral (DHT, NeoPixel)	{}	No MATLAB bus dependency
I2C device using SW_I2C (displays, most sensors)	{}	Software I2C bypasses MATLAB's bus
I2C device delegating to MATLAB's I2C infrastructure	{'I2C'}	MATLAB manages Wire init and pins
SPI device	{}	MATLAB does not own SPI bus
Uses another custom addon	{'OtherAddon/Name'}	Chain dependency

LibraryHeaderFiles Format

Format: '<FolderNameInCLIRoot>/<HeaderFilename>'

% GOOD — folder name matches what's in CLIRoot/user/libraries/
LibraryHeaderFiles = {'DHT/DHT.h'}
LibraryHeaderFiles = {'U8g2/U8g2lib.h'}
LibraryHeaderFiles = {'Adafruit_Motor_Shield_V2_Library/Adafruit_MotorShield.h'}

% BAD — just filename without folder
LibraryHeaderFiles = {'DHT.h'}

% BAD — subdirectory path (NEVER include src/ even if the file physically lives there)
LibraryHeaderFiles = {'U8g2/src/U8g2lib.h'}

% BAD — Arduino library name (Wire is not in CLIRoot/user/libraries)
LibraryHeaderFiles = {'Wire/Wire.h'}

The Arduino build system automatically searches the src/ subdirectory within the library folder, so NEVER include src/ in this path. This is the most common mistake — even though headers like U8g2lib.h physically reside in <LibFolder>/src/, you must write 'U8g2/U8g2lib.h' NOT 'U8g2/src/U8g2lib.h'.

C++ Header Rules

Read references/cpp-patterns.md for full templates. Critical rules:

1. setup() MUST NOT initialize hardware — calling .begin(), Wire.begin(), SPI.begin() etc. in setup() causes "Internal error: The initialization of the server code is incorrect." Simple variable assignments (e.g., cursorRow = 0) are safe.
2. Use lazy initialization — init hardware on first command via a dedicated INIT command
3. sendResponseMsg must send >= 1 byte — sendResponseMsg(cmdID, 0, 0) crashes ARM boards (UNO R4, ESP32)
4. NEVER #include <Wire.h> in your addon header — causes I2C bus conflict with MATLAB. Your code must never contain this line. Third-party libraries may include it internally (that is fine — you don't control their code), but YOUR .h file must not.
5. #include <SPI.h> is safe — MATLAB does not own SPI
6. Use angle brackets for third-party headers: #include <U8g2lib.h>
7. Use constructor initializer list for member objects, not in-class initialization

I2C Bus Conflict — Read references/bus-conflicts.md

MATLAB owns the hardware I2C bus (Wire). If your peripheral uses I2C:

• Preferred: Use software I2C constructors (e.g., U8G2_..._SW_I2C) with DependentLibraries = {}
• Do NOT call Wire.begin() directly
• Do NOT #include <Wire.h> in your own addon header

If the third-party library requires hardware I2C (e.g., SGP30, motor shields): set DependentLibraries = {'I2C'} and let MATLAB manage the bus. The third-party library may include Wire.h internally — this is safe because MATLAB has already initialized Wire. Your C++ code must NOT call Wire.begin() since MATLAB already did.

Common Mistakes

Mistake	Why It's Wrong	Correct Approach
DependentLibraries = {'Wire'}	Wire is not in listArduinoLibraries	Use {} or {'I2C'}
Third-party lib in +arduinoioaddons/src/	Wrong location; build can't find it	arduinoio.CLIRoot/user/libraries/
LibraryHeaderFiles = {'U8g2lib.h'}	Missing folder prefix	{'U8g2/U8g2lib.h'}
U8G2_..._HW_I2C constructor	Conflicts with MATLAB's Wire management	Use _SW_I2C constructor
.begin() calls in setup()	Server handshake fails	Init hardware via command; variable assignments are OK
sendResponseMsg(cmdID, 0, 0)	Crashes ARM boards (nullptr)	Send >= 1 byte always
#include <Wire.h> in your addon header	Conflicts with MATLAB I2C server	Omit; use SW_I2C or DependentLibraries = {'I2C'}
Installing via Arduino IDE Library Manager	MATLAB uses its own CLIRoot path	Use downloadLibrary()
Not calling addpath after creating addon	listArduinoLibraries won't find it	addpath + savepath

Conventions

• Always check native support first, File Exchange second, create last
• Always use downloadLibrary (R2025a+) or manual copy to CLIRoot for third-party libs
• Always verify with listArduinoLibraries after registration
• Never call .begin() or hardware init in setup() — use lazy init via dedicated command
• Always send >= 1 byte in sendResponseMsg
• Never include <Wire.h> in your own code — use software I2C or depend on {'I2C'}
• Never put third-party Arduino libraries inside +arduinoioaddons
• Prefer createLibraryTemplate (R2025a+) over manual folder creation

Fallback: When Automated Steps Fail or Take Too Long

If listArduinoLibraries hangs, File Exchange search takes too long, downloadLibrary fails, or createLibraryTemplate fails — fall back to the pre-R2025a manual approach:

1. Install library manually: Download the third-party Arduino library .zip and extract it into fullfile(arduinoio.CLIRoot, 'user', 'libraries', '<LibName>').
2. Create folder structure manually:

   <targetDir>/+arduinoioaddons/+<FolderName>/<ClassName>.m
   <targetDir>/+arduinoioaddons/+<FolderName>/src/<HeaderName>.h
   

3. Register manually: addpath('<targetDir>'); savepath;
4. Continue from Step 5 (configure MATLAB class and C++ header as normal).

Do not retry failing commands repeatedly. Switch to manual creation and proceed.

Troubleshooting

When errors occur during deployment or usage, read the appropriate reference:

• Compilation or "source not found" errors → read references/common-errors.md
• Runtime errors ("unable to receive data", "server code incorrect") → read references/common-errors.md
• Bus conflicts (I2C/SPI/UART) → read references/bus-conflicts.md
• C++ code patterns (lazy init, response format, includes) → read references/cpp-patterns.md

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Copyright 2026 The MathWorks, Inc.

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