Turn on the LED with a serial command.
Arduino / C: Wait for the character 1 in Serial Monitor before turning on the built-in LED.
void setup() {
Serial.begin(9600);
pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, LOW);
Serial.println("Send 1 to turn on the LED");
}
void loop() {
if (Serial.available() > 0) {
char command = (char)Serial.read();
if (command == '1') {
digitalWrite(LED_BUILTIN, HIGH);
Serial.println("LED on");
}
}
}Expected output EXAMPLE
Send 1 to turn on the LED LED on
Details
Targets Arduino Uno R3 (ATmega328P, 16 MHz) with the Arduino AVR core. Open as a sketch in the Arduino IDE and select Arduino Uno. Serial output uses 9600 baud. Tested with simavr; electrical characteristics and physical wiring are outside this simulation. Open Serial Monitor at 9600 baud, choose No line ending, enter 1 and click Send. Single quotes represent the character 1; it is different from the integer 1. Other characters are ignored. The test injects one 1 and verifies that D13 changes from low to high.
Tested on Ubuntu 24.04.5 LTS · · Uno R3 / ATmega328P at 16 MHz; simavr 1.6+dfsg-3build2 · simavr 1.6+dfsg-3build2; arduino-cli Version: 1.5.1 Commit: 01f3d4f2b Date: 2026-06-05T10:22:17Z; Arduino AVR core 1.8.6
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Snippet process uid 65534 with a read-only root filesystem and temporary working files. Networking disabled. The exact sketch was compiled for Uno R3 and simulated at 16 MHz. UART output is shown below; compiler logs and measured GPIO traces are retained in the test evidence. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged process) / C.UTF-8
- Interpreter invocation
arduino-cli compile --fqbn arduino:avr:uno; uno-sim sketch.ino.elf (capture UART and D13 transitions)- Container image ID
sha256:ec91410a8f6ec3e985830b5e3a0560306d36f8c1c5ccd91a6699abe707123fa3- Code SHA-256
873aeeb07b7d236c1de936b2177059e5e4e965c3970f31f0acc97d05ea37cc66- Dependencies
- simavr 1.6+dfsg-3build2; arduino-cli Version: 1.5.1 Commit: 01f3d4f2b Date: 2026-06-05T10:22:17Z; Arduino AVR core 1.8.6
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
Simulator inputs: {"sim_ms": 500, "serial_input": "1", "pin_input": "none"}
Observed standard output
Send 1 to turn on the LED LED on
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.
Additional assertions that passed
Checks recorded by the test harness. Where Python assertions are shown, browser cases use Playwright and simulator cases may inspect pin transitions: result.stdout is captured output, work is the temporary directory, and Path is pathlib.Path. The harness also imports json and csv.
trace = [tuple(map(int, line.split(','))) for line in Path('pin13.csv').read_text().splitlines()]
assert any(value == 0 for cycle, value in trace) and trace[-1][1] == 1