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Justina—short for “Just an Interpreter for Arduino”—lets you enter and run a structured, Basic-like language on supported Arduino boards instead of compiling every program statement into machine code. Install its Arduino library, upload a small interpreter sketch, then use a serial terminal to evaluate expressions, issue commands, or run program files. It is intended for learning and rapid prototyping; it still depends on Arduino hardware and can be extended with C++ when a project needs board-specific or time-critical work.
What Justina does
Justina is an interpreted programming language and Arduino library created by Herwig Taveirne. An interpreter parses statements into tokens and executes them on the board. The Arduino sketch provides the interpreter and access to the board; you can then interact with it at a prompt rather than recompiling and uploading for every language-level change.
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The author described it as “a fully documented, structured, easy-to-use programming language for Arduino” intended for fast prototyping in a Hackster project description dated 10 June 2024. The project page and user manual published 29 May 2024 describe a language that is approachable and structured while retaining Arduino-oriented functions. Justina is not a replacement for Arduino’s C++ environment in every project: the interpreter runs within an Arduino sketch, and C++ remains available for integration and extensions.
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Which boards are documented
The documented and tested targets are three 32-bit Arduino Nano boards. The project author prefers the Nano ESP32, citing relatively fast compilation and more memory than the Nano 33 IoT; the project does not publish benchmark timings or memory-footprint measurements.
#1 Best Overall
- 35+ Guided Electronics Projects: Progress from LEDs and buttons to RFID access, real-time clocks, motion and distance sensing, environmental monitoring, motor control and interactive displays for STEM learning, coding clubs and maker projects
- More I/O and Memory for Larger Builds: The MEGA 2560 R3 provides 54 digital I/O pins, including 15 PWM outputs, 16 analog inputs, 4 hardware serial ports and 256 KB flash for projects that combine more sensors, controls and displays
- 200+ Components for Prototyping: Includes LCD1602, RC522 RFID, RTC, DHT11, HC-SR501 PIR, ultrasonic and water-level sensors, GY-521, MAX7219, keypad, joystick, rotary encoder, relay, SG90 servo, stepper motor, DC motor, breadboard and more
- Learn, Modify and Create: Follow 35+ guided lessons with example code, then adjust sensor thresholds, timing, display text, motor behavior and control logic to turn structured exercises into access systems, monitors, alarms and interactive projects
- Organized for Repeatable Learning: Pre-soldered modules, a solderless breadboard, storage case and small-parts box reduce setup time and keep sensors, LEDs, ICs, wires and other components easy to find between projects
| Board | Documented status | Notes |
|---|---|---|
| Arduino Nano 33 IoT | Documented and tested | The author says the Nano ESP32 has more memory. |
| Arduino Nano ESP32 | Documented and tested | The author’s preferred target; compilation is described as relatively fast. |
| Arduino Nano RP2040 | Documented and tested | Included among the project’s supported boards. |
Compatibility beyond these three documented boards is not established by the cited project material. Choose a tested target if you want to follow the supplied examples as written.
Install it and try the prompt
- In Arduino IDE, open Tools → Manage Libraries, search for “Justina,” and install Justina interpreter.
- Select a documented board and its port: Nano 33 IoT, Nano ESP32, or Nano RP2040.
- Open Examples from Custom Libraries and choose Justina_easy.
- Compile and upload the example sketch.
- Open Serial Monitor at the baud rate configured by the sketch. The manual’s starter sketch uses 115200 baud. Enter an expression or command at the
Justina>prompt.
The IDE’s Serial Monitor is enough for basic command entry. For sending program files or working with additional stream devices, the manual recommends using a separate terminal such as YAT. The supplied examples also cover a minimal interpreter sketch, callbacks, OLED output, and language programs.
Rank #2
- TURN CODE INTO REAL-WORLD RESULTS — Follow 22+ guided lessons to make LEDs blink, read temperature and distance, move servo and stepper motors, control an LCD and respond to joystick or IR input; ideal for a family weekend build, homeschool unit, coding club or STEM classroom
- MORE PROJECT VARIETY IN ONE ORGANIZED KIT — Includes the UNO R3 controller, LCD1602 with pre-soldered header, breadboard power module, ultrasonic and DHT11 sensors, joystick, IR receiver and remote, SG90 servo, stepper motor, relay, DC motor, fan blade, displays, LEDs, buttons, resistors and jumper wires
- START WITHOUT SOLDERING — Plug-in modules, a solderless breadboard and the pre-soldered LCD help beginners focus on wiring, code and testing; the illustrated component list makes it easier to find each part and move from one lesson to the next
- LEARN THE LOGIC, THEN CREATE YOUR OWN — Use Arduino IDE and the included example code to understand digital input and output, analog sensing, timing, motor control and display functions, then change thresholds, speeds and sequences for alarms, environmental monitors, reaction games and motion projects
- CLEAR SETUP SUPPORT FOR FIRST-TIME BUILDERS — Download the latest tutorial and code, select the UNO board and correct computer port, check component polarity and breadboard rows, and keep power-module input at 9V or below; younger learners should work with an experienced adult
What the language can express
Justina offers scalar integers, floating-point values and strings, as well as arrays, variables and constants. Its structured constructs include loops and conditional statements. Operators cover arithmetic, comparisons, logic, bitwise operations, assignment, increment and exponentiation, and display formatting can be configured.
The manual lists more than 250 built-in functions, commands and operators, plus 70-plus predefined symbolic constants; it also describes more than 30 functions for Arduino I/O ports and memory. Those are counts reported by Herwig Taveirne in the 2024 manual, not independent measurements of coverage. The breadth means the language is more than a prompt for arithmetic, but you should consult the manual for exact function names and behavior before relying on a particular peripheral or operation.
Rank #3
- 30+ Guided Electronics Projects: Start with LEDs and build toward LCD1602 displays, RFID access, motion detection, distance sensing, motor control and environmental monitoring for STEM learning, coding clubs, classrooms and hobby projects
- 200+ Components Across 63 Types: Includes an ELEGOO UNO R3 controller, LCD1602, RC522 RFID, RTC, HC-SR501 PIR sensor, ultrasonic sensor, DHT11, GY-521, MAX7219, keypad, joystick, relay, SG90 servo, stepper motor, breadboard and more
- Begin Without Soldering: Pre-soldered modules, a solderless breadboard, organized storage case and small-parts box reduce setup time and help beginners move from lesson to lesson while keeping LEDs, ICs, wires and sensors easy to find
- Learn, Modify and Create: Program the ELEGOO UNO R3 board with Arduino IDE using the included PDF tutorial and example code, then adjust sensor thresholds, timing, display text and motor behavior to turn guided lessons into original projects
- Flexible Power and Project Setup: Includes a 9 V, 1 A power supply, breadboard power module, 9 V battery and USB cable to support controller, breadboard and module experiments without sourcing basic setup accessories separately
How it compares with Arduino C++
| Consideration | Justina | Arduino C++ |
|---|---|---|
| Trying a change | Enter statements interactively or run a language program through the interpreter. | Typically edit the sketch, compile it, and upload it to the board. |
| Syntax and learning | Structured, non-object-oriented and Basic-like, aimed at a simpler command-driven workflow. | Uses C++ syntax and Arduino’s sketch model, offering the broader programming environment of C++. |
| Errors and debugging | Reports parsing and execution errors with numbers. Debug mode provides breakpoints, stepping, watched expressions, variable inspection and call-stack review. | Uses the compiler and the tools available in the Arduino development environment; the available project documentation does not establish a like-for-like debugging comparison. |
| Hardware access | Includes Arduino-oriented functions and can use configured streams and connected peripherals. | Can directly use Arduino libraries and C++ code. |
| Board resources | Runs an interpreter on the board, so available memory and processing capacity are relevant; published footprint figures are not stated. | Compiles the sketch to run on the board; a quantitative performance comparison is not available. |
| Extension | C++ system and user callbacks can handle background work or add hardware-specific and time-critical functions. | Hardware-specific functionality can be implemented directly in C++. |
Justina’s clearest advantage is the interactive workflow and its more approachable syntax for small experiments. Its trade-off is that interpreted programs operate within the interpreter and the board’s constraints. The cited sources provide no benchmark timings or memory measurements, so they do not support a claim that Justina is faster or more efficient than C++.
Debugging and extending a program
Justina distinguishes parsing errors—problems interpreting the statement—from execution errors encountered while running it. Both categories carry error numbers, which help identify what went wrong. In debug mode, the documented tools include:
Rank #4
- All-in-One Starter Kit for Beginners: Part of the Powered by Arduino program, this kit includes an original Arduino UNO R4 WiFi, 300+ high-quality components, 50+ hands-on projects (30 basic, 13 fun, and 8 IoT), and 100+ free video lessons co-created with renowned educator Paul McWhorter. Designed for beginners ages 8+, it provides a complete, step-by-step path to learn Arduino, electronics, coding, and IoT. RoHS compliant for added safety and quality, it also makes a thoughtful gift for tech enthusiasts, students, and aspiring makers for birthdays, holidays, and special occasions
- Powerful Arduino Uno R4 WiFi Board: Upgraded from the Arduino Uno R3, the Arduino Uno R4 WiFi features a 32-bit processor, more memory, and built-in WiFi and Bluetooth, enabling connection to third-party apps for more interactive and practical projects.
- 300+ Components for Endless Possibilities: With 300+ components and sensors, this kit is perfect for portable projects. It features step-by-step tutorials, open-source code, and compatibility with other Arduino boards like Uno R3 and Nano, offering endless customization and learning opportunities.
- Engaging Projects for Every Skill Level: Featuring 50 projects (30 basic, 13 fun, 8 IoT) with IoT app integration like Arduino IoT Cloud , this kit supports Arduino C++ programming, making it perfect for students, teachers, and engineers to learn, code, and create at any skill level.
- Dedicated Support for Beginners: Alongside online resources and video tutorials, SunFounder provides technical support and troubleshooting forums to help beginners solve programming challenges with ease.
- Breakpoints, including trigger expressions or hit counts.
- Single-stepping through program execution.
- Watched expressions and inspection of local and static variables.
- Call-stack review.
C++ callbacks provide a bridge to code that should run periodically or needs hardware-specific behavior. System callbacks can handle housekeeping such as TCP maintenance; registered user callbacks can add functions or cover time-critical tasks. This makes Justina useful alongside C++, rather than requiring every part of an application to be written in the interpreted language.
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Serial is the default console, but the manual describes configuring other Serial, TCP/IP, SPI and I2C streams, with up to four I/O devices. The exact devices and functions available depend on connecting and configuring the relevant hardware.
Best Value
- The most economical kit comes with everything compatible with Arduino to starting programming for beginners .
- This is the upgraded starter kits come with a 9V 1A Power Adapter (At least $5.99 on amazon) to replace a 9V Battery , and the Lcd1602 module come with pin header(not need to be soldered by yourself).
- Include High Quality Base Board base on Arduino UNO R3 compatible with Arduino IED and Sensors, Servo, Motor, ULN2003 driver board, lcds, etc.
- Free PDF Tutorial and Datasheet are available to download from our official website or you can contact our customer service.
- All of the Components and Integrated Circuits are individually packaged and labeled, and packing in a plastic box which is bigger enough for you.
- Displays: An OLED or LCD can be added as another stream or device; the supplied examples include OLED use.
- SD-card files: With an SD-card breakout connected over SPI, Justina can open, read, write and list files, and process file contents.
- Network and peripherals: TCP/IP and SPI/I2C devices are possible when the appropriate hardware and stream configuration are in place.
These are optional integrations, not requirements for using the basic serial prompt. Check the manual and examples for the configuration needed for a specific device.
When Justina is a good fit
- Try it when you want an interactive, Basic-like way to experiment on one of the documented Nano boards, or want to build small programs without repeating the edit-compile-upload cycle for each language statement.
- Keep C++ central when your project depends on capabilities or libraries not established in Justina’s documentation, or when you need direct control over performance and resource use.
- Use both when an interpreted command interface is convenient but background tasks, peripheral support or time-critical behavior are better handled in C++ callbacks.
The project’s own documentation and examples are the best guide to supported syntax and hardware functions: Justina project page and manual.
Quick Recap
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