delayMicroseconds(10)
Creates the trigger pulse required by HC-SR04 style modules.
Arduino sample guide
roboda-sample-0182 - Ultrasonic Distance 08
Measure distance with an ultrasonic trigger/echo module.
Step-by-step build
Measure obstacle distance with trigger and echo timing.
1
Wire TRIG and ECHO to the listed pins.
2
Send a short trigger pulse.
3
Measure echo pulse time with pulseIn().
4
Convert travel time into distance in centimeters.
Important code parts
These are the sections learners should understand before changing the sketch.
pulseIn(echoPin, HIGH)
Measures how long the echo pin stays HIGH.
duration * 0.0343 / 2
Uses speed of sound and divides by two for the out-and-back trip.
Pin mapping for this sample
Use this first table for the exact sample wiring, then use the board-family table when moving the sketch to another Arduino board.
| Code name | Sample pin | Mode | Connect to | Note |
|---|---|---|---|---|
| trigPin | D9 | OUTPUT | HC-SR04 TRIG | Sends a 10 microsecond pulse. |
| echoPin | D11 | INPUT | HC-SR04 ECHO | 3.3V boards need level shifting for 5V echo modules. |
Arduino board pin reference
The code names stay the same; only the physical board pins may change by family. Always confirm with the board silkscreen when using clones or special variants.
| Board family | Digital | PWM | Analog | I2C | SPI | Interrupt |
|---|---|---|---|---|---|---|
| Uno / Nano / Pro MiniDefault target for these samples. | D0-D13 | D3, D5, D6, D9, D10, D11 | A0-A5 | A4 SDA, A5 SCL | D10 SS, D11 MOSI, D12 MISO, D13 SCK / ICSP | D2, D3 |
| Mega 2560Best for many sensors or multiple serial ports. | D0-D53 | D2-D13, D44-D46 | A0-A15 | D20 SDA, D21 SCL | D50 MISO, D51 MOSI, D52 SCK, D53 SS / ICSP | D2, D3, D18, D19, D20, D21 |
| Leonardo / MicroUSB serial can behave differently because the main MCU handles USB. | D0-D13 | D3, D5, D6, D9, D10, D11, D13 | A0-A5 plus extra analog-capable pins by board | D2 SDA, D3 SCL | ICSP header | D0, D1, D2, D3, D7 |
| Nano Every / Uno WiFi Rev2Check the board package pinout for exact PWM labels. | D0-D13 | PWM-marked digital pins | A0-A7 on Nano Every, A0-A5 on Uno WiFi Rev2 | SDA/SCL marked pins | ICSP/SPI marked pins | Use pins supported by digitalPinToInterrupt() |
| Uno R4 Minima / Uno R4 WiFi5V logic board; still confirm shield/library compatibility. | D0-D13 | PWM-marked digital pins | A0-A5 | SDA/SCL marked pins | ICSP/SPI marked pins | Use digitalPinToInterrupt(pin) |
| Due3.3V logic only; protect pins from 5V sensors. | D0-D53 | PWM-marked digital pins | A0-A11 | SDA/SCL and SDA1/SCL1 | SPI header | Use digitalPinToInterrupt(pin) |
| MKR / Nano 33 family3.3V logic. Some AVR-only libraries may need alternatives. | Board-marked digital pins | PWM-marked pins | Board-marked analog pins | SDA/SCL marked pins | SPI marked pins | Use digitalPinToInterrupt(pin) |
Full sample code
/*
Roboda verified Arduino sample 0182
Feature: Ultrasonic Distance
Generated for online build, classroom practice, and hardware upload testing.
*/
const byte trigPin = 9;
const byte echoPin = 11;
void setup() {
Serial.begin(9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}
void loop() {
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
unsigned long duration = pulseIn(echoPin, HIGH, 30000UL);
float distanceCm = duration * 0.0343 / 2.0;
Serial.println(distanceCm);
delay(325);
}
Teacher notes
- Compile the sample before changing wiring or constants.
- When changing boards, keep the code names the same and update only the pin number constants.
- For 3.3V boards, level-shift 5V sensors and modules before connecting signal pins.
- Use the first compiler error and the Roboda diagnostic suggestion before fixing later warnings.