Version 11 — 16 libraries, 12 boards, full IDE

Write code that
touches hardware

A LISP-based operating system for Arduino and embedded systems. Write programs in a clean, elegant language that runs on real hardware, in a circuit simulator, or headlessly on your machine.

Download for your platform Try it live →
hil-cli simulate morse-sos.hil
✓ hil-cli simulate morse-sos.hil {"type":"ready","msg":"Connected on none"} [LOG] >> Initiating Emergency SOS Beacon... [LOG] -> Transmitting: S O S [LOG] -> Transmitting: S O S [LOG] -> Transmitting: S O S [LOG] >> Beacon transmission complete. ✓ Script completed successfully
15+
Operators
52
Examples
16
Libraries
0
Dependencies
Try it now

Interactive LISP Terminal

Type an expression, press Enter. Results appear instantly. Multi-line: Shift+Enter.

hil-os — interactive LISP terminaltype HELP for commands
Welcome to HIL-OS LISP v9.5. Type an expression and press Enter.
SET variables, call operators, define functions. Multi-line with Shift+Enter.
Type HELP for commands, CLEAR to reset, or try: (+ 10 5)
 
>
Try:
Features

Everything you need to
program hardware

From blinking an LED to running PID controllers, HIL-OS gives you the full stack.

⚡

Clean LISP Syntax

Write elegant code with S-expressions, variables, functions, and recursion. No semicolons, no braces, no boilerplate.

🔌

Real Hardware

Direct access to digital/analog pins, I2C, SPI, servo motors, LCD displays, NeoPixels, and more on Arduino boards.

🧪

CRUMB Simulator

Transpile your code to Arduino C and simulate it in the CRUMB circuit simulator — no hardware required.

🔄

Dual Target

The same LISP code runs on real Arduino hardware AND the CRUMB simulator. Write once, deploy anywhere.

🎯

15+ Operators

Arithmetic, boolean logic, comparisons, math utilities, loop control — everything for embedded programming.

📦

16 Arduino Libraries

I2C, SPI, Servo, LCD, NeoPixel, DHT, SD card, MP3, RTC, BMP280, MAX7219, Motor, TFT, and more via USE-* forms.

💻

12 Boards

Arduino Uno/Nano/Mega, ESP32/S2/S3, ESP8266, RP2040 Pico, Leonardo, Nano Every, Seeed XIAO, and SparkFun.

🎨

HIL IDE

Full-featured desktop IDE with Monaco editor, auto-complete for all LISP forms, syntax highlighting, and one-click transpilation.

📦

Zero Dependencies

Single binary. No Node.js, no Python, no npm. Download and run on Windows, macOS, or Linux.

How it works

From LISP to hardware
in three steps

.hil
LISP source
→
Parser
S-expressions
→
Transpiler
LISP → C
→
Arduino C
.ino file
.ino
C source
→
avr-gcc
Compiler
→
.hex
Firmware
→
Arduino
Real hardware
Or: .hex → CRUMB Simulator for visual testing
Compare

LISP vs Arduino C

Same functionality, radically simpler syntax.

Blink an LED
HIL-OS LISP

(WRITE D 13 1)
(DELAY 500)
(WRITE D 13 0)
(DELAY 500)
Arduino C

digitalWrite(13, HIGH);
delay(500);
digitalWrite(13, LOW);
delay(500);
Read sensor + decision
HIL-OS LISP

(SET temp (LM35 0))
(IF (>= temp 30)
  (TONE 11 1000 200))
Arduino C

float temp = analogRead(A0)
  * 5.0 / 1024 * 100;
if (temp >= 30)
  tone(11, 1000, 200);
FOR loop with math
HIL-OS LISP

(SET sum 0)
(FOR i 0 10
  (SET sum (+ sum i)))
; sum = 45
Arduino C

int sum = 0;
for (int i = 0; i < 10; i++) {
  sum += i;
}
// sum = 45
Code

Simple, powerful, expressive

From beginner-friendly blink to advanced state machines — HIL-OS scales with your skills.

Blink an LED
1; Turn LED on pin 13 on and off 2(WHILE 1 3 (DO 4 (WRITE D 13 1) 5 (DELAY 500) 6 (WRITE D 13 0) 7 (DELAY 500)))
Boolean Logic
1(SET temp 25) 2(SET humid 70) 3 4(IF (AND (>= temp 20) (> humid 60)) 5 (LOG "Comfortable") 6 (LOG "Adjust!"))
State Machine with COND
1(SET state 0) 2 3(COND 4 ((== state 0) (LOG "IDLE")) 5 ((== state 1) (LOG "RUNNING")) 6 (1 (LOG "UNKNOWN")))
FOR Loop + Break
1(SET sum 0) 2(FOR i 0 10 3 (DO 4 (IF (== i 5) (BREAK)) 5 (SET sum (+ sum i)))) 6; sum = 0+1+2+3+4 = 10
Community

Built for makers

"Finally, a way to prototype embedded code without wiring up breadboards every time. The simulation mode is a game changer."
— Maker community
"The LISP syntax is so clean. I wrote a PID controller in 10 lines. In C it was 50. The transpiler just works."
— Robotics hobbyist
"I teach embedded systems. HIL-OS lets students focus on logic, not syntax errors. They see results in seconds."
— Engineering educator
Reference

Complete language at a glance

Operators

+ - * / %Arithmetic
== != > < <= >=Comparison
AND OR NOTBoolean logic
MIN MAX ABSMath utilities
MAP CONSTRAIN RANDOMRange & random

Control Flow

IF CONDConditionals
WHILE FORLoops
BREAK CONTINUELoop control
DEFUNFunctions
DO SET EXITBlocks & assignment
Get started

Start coding in
30 seconds

Download, extract, run. No accounts, no cloud, no setup wizards.

Download HIL-OS Start tutorial →
Download

Pick your platform

Pre-built binaries for Windows, macOS, and Linux. Zero dependencies.

🪨
Windows
x64 • .exe
Download
🍎
macOS
Intel + Apple Silicon
Download
🐧
Linux
x64 • binary
Download

Or download the complete package:

Full package (27 MB)
Desktop IDE

HIL LISP IDE

A native desktop IDE for writing, transpiling, and uploading HIL LISP code. Monaco editor, syntax highlighting, serial monitor, and one-click transpilation.

🪨
Windows
x64 • .exe
Download
🍎
macOS
Intel (x64)
Download
🍎
macOS
Apple Silicon (arm64)
Download
🐧
Linux
x64 • binary
Download