Week 9. Input Devices¶

Hero Shot

This week we were introduced with different input devices which are present in our lab. Same as previous week I did both group assignment and individual assignment. For individual assignment, I tried exploring on distance sensor, microwave radar motion sensor and HC-SR04 ultrasonic distance sensor. In the group we tried exploring the logic analyser and oscilloscope for studying the multiple digital and analog signals.

Assignments for the Week¶

Group Assignment:

Probe an input device(s)’s analog levels and digital signals.
Document your work on the group work page and reflect on your individual page what you learned.

Link to the group Assignment is here

key takeaways from this week

While doing individual Assignment I came across many areas in which I was not able to upload the code which is because in some cases my codes were wrong and I had connected to wrong pins. So what I had concluded was always make sure you connect to right pins with right code for the program to execute.

Individual Assignment:

Add a sensor to a microcontroller board that you have designed and read it.

VL53L1X Distance Sensor¶

The VL53L1X is a distance sensor and can measure distances super accurately, even in the dark or bright light.

Specifications

Operating voltage: 3.3V/5V
Dimension: 20mm × 24mm
Mounting holes size: 2.0mm
Ranging distance: 40 ~ 4000mm
Ranging accuracy: ±5%
Ranging time (min): 20ms (short distance mode), 33ms (medium/long distance mode)
Field of view: 27°
Laser wavelength: 940nm
Operating temperature: -20 ~ 80°C

Pinouts

VCC: 3.3V/5V power input

GND: ground
SDA: I2C data pin
SCL: I2C clock pin
SHUT: shutdown control, connects to IO pin
INT: interrupt output, connects to IO pin

Dimensions

Set up for my XIAO RP2040 board

VCC - 5V
GND - GND
SDA - SDA (D4)
SCL - SCL (D5)

After I finished connecting the distance sensor with my board, I opened the Arduino IDE and downloaded the library for VL53L1X from library manager.

Next I compiled and uploaded the code to see whether the distance sensor will work with my board or not

This is the code which I used for programing

 #include <Wire.h>
 #include <VL53L1X.h>

 VL53L1X sensor;
 const int ledPin = A0;  // LED connected to pin A0
 const int triggerDistance = 300; // Trigger distance in mm (30 cm)

 void setup() {
 Serial.begin(115200);
 Wire.begin();
 Wire.setClock(400000); // Set I2C clock speed to 400kHz

 pinMode(ledPin, OUTPUT); // Set A0 as an output

 sensor.setTimeout(500);
 if (!sensor.init()) {
 Serial.println("Failed to detect and initialize sensor!");
 while (1);
 }

 sensor.setDistanceMode(VL53L1X::Long);  // Set sensor to long distance mode
 sensor.setMeasurementTimingBudget(50000);  // Set timing budget (50ms)
 sensor.startContinuous(50);  // Start continuous measurements every 50ms
 }

 void loop() {
 sensor.read();  // Get new sensor reading
 int distance = sensor.ranging_data.range_mm;  // Store measured distance
 int status = sensor.ranging_data.range_status; // Get measurement status

 Serial.print("Distance: ");
 Serial.print(distance);
 Serial.print(" mm\tStatus: ");
 Serial.print(status); // Print status code
 Serial.print("\tSignal: ");
 Serial.print(sensor.ranging_data.peak_signal_count_rate_MCPS);
 Serial.print("\tAmbient: ");
 Serial.println(sensor.ranging_data.ambient_count_rate_MCPS);

 // Check if object is within 30 cm AND measurement is valid (status == 0)
 if (distance <= triggerDistance && status == 0) {
 digitalWrite(ledPin, HIGH);  // Turn LED ON
 } else {
 digitalWrite(ledPin, LOW);  // Turn LED OFF
 }

 delay(50);  // Small delay for stability
 }

RCWL-0516 Microwave Radar Motion sensor¶

The RCWL-0516 is a microwave motion sensor that detects movement using Doppler radar technology. It is commonly used in projects like automatic lighting systems, security systems, and other motion-activated applications

Specifications

Operating Voltage: 4V–28V (typically 5V)
Operating Current: ~3mA (low power consumption)
Output Voltage: 3.3V or 5V (matches input voltage)
Detection Range: 5–7 meters (adjustable)
Detection Angle: 360 degrees (omnidirectional)
perating Frequency: 3.18 GHz (microwave Doppler radar)
Output Signal: HIGH (3.3V/5V) when motion detected, LOW (0V) otherwise
Repeat Trigger: Yes (output stays HIGH as long as motion is detected)
Operating Temperature: -20°C to 80°C

Pinouts

The RCWL-0516 has 5 pins:

VIN:
Power supply input (4V–28V, typically 5V).
GND:
Ground (0V).
OUT:
Output pin (goes HIGH when motion is detected).
CDS:
Light-dependent resistor (LDR) input (optional, used to disable the sensor in daylight).
3V3:
3.3V output (can power other devices)

Dimensions

Set up for my XIAO RP2040 board

VCC - 5V
GND - GND
OUT - A2

I connected the RCWL-0516 microwave radar motion sensor with my board ensuring all the connections are being made correctly with right pins.

After that I opened the Arduino IDE and installed the library for RCWL-0516 from the library manager.

Next I compiled and uploaded the code in arduino IDE to see how the sensor communicated with my board.

This is the code which I used for programing

 // Pin definitions
 const int motionSensorPin = A2;  // RCWL-0516 output pin connected to XIAO RP2040 (A2)
 const int ledPin = A0;            // Built-in LED connected to pin A0

 void setup() {
 // Initialize the serial communication
 Serial.begin(115200);

 // Set the motion sensor pin as input
 pinMode(motionSensorPin, INPUT);

 // Set the LED pin as output
 pinMode(ledPin, OUTPUT);
 digitalWrite(ledPin, LOW);  // Ensure the LED is off initially
 }

 void loop() {
 // Read the motion sensor value
 int motionDetected = digitalRead(motionSensorPin);

 if (motionDetected == HIGH) {
 // Motion detected (assume within 2 cm)
 digitalWrite(ledPin, HIGH);  // Turn LED on
 Serial.println("Welcome! How may I help you?");  // Print welcome message
 } else {
 // No motion detected
 digitalWrite(ledPin, LOW);  // Turn LED off
 Serial.println("Thank you! Visit soon.");  // Print goodbye message
 }

 // Small delay to avoid flooding the serial monitor
 delay(500);
 }

The video below shows the short simulation of using RCWL-0516 microwave radar motion sensor

HC-SR04 Ultrasonic Distance Sensor¶

The HC-SR04 is a popular ultrasonic sensor used for non-contact distance measurements. This sensor operates by emitting an ultrasonic sound pulse and measuring the time it takes for the echo to return to calculate the distance to an object.

Specifications

Operating Voltage: 5V DC
Current Consumption: ~15mA
Frequency: 40kHz
Measuring Range: 2 cm to 400 cm (0.79 in to 157 in)
Resolution: 0.3 cm (3 mm)
Measuring Angle: ~15 degrees
Trigger Input: 10µs TTL pulse
Echo Output: TTL signal proportional to the distance

Pinouts

VCC – 5V power supply
Trig – Trigger input (high for 10µs to initiate measurement)
Echo – Output signal (high time corresponds to distance)
GND – Ground

Dimensions

Set up for my board

VCC - 5V
Trig - A1
Echo - A2
GND - GND
Led - D8

Next I made connection and set up the circuit in which I had connected the Trig pin to A1 and Echo pin to A2 and the external led to D8 of Xiao RP2040

Followed by that I opened the Arduino IDE and downloaded the library for HC-SR04 ultrasonic distance sensor from the library manager

Attached beleow is the code which I used for programing

 const int trigPin = A1;    // A1 = GPIO27
 const int echoPin = A2;    // A2 = GPIO28
 const int ledPin = 2;      // D8 = GPIO8

 void setup() {
 pinMode(trigPin, OUTPUT);
 pinMode(echoPin, INPUT);
 pinMode(ledPin, OUTPUT);
 Serial.begin(115200);
 Serial.println("System started. Waiting for sensor data...");
 }

 void loop() {
 // 1. Trigger ultrasonic pulse
 digitalWrite(trigPin, LOW);
 delayMicroseconds(2);
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10);
 digitalWrite(trigPin, LOW);

 // 2. Measure echo duration
 long duration = pulseIn(echoPin, HIGH);
 int distance = duration * 0.034 / 2;

 // 3. Debug outputs (critical for troubleshooting)
 Serial.print("Distance: ");
 Serial.print(distance);
 Serial.print("cm | LED state: ");
 Serial.println(digitalRead(ledPin));

 // 4. Blink logic (when object ≤4cm)
 if (distance > 0 && distance <= 4) {
 digitalWrite(ledPin, HIGH);
 delay(500); // LED ON for 500ms
 //digitalWrite(ledPin, LOW);
 //delay(500); // LED OFF for 500ms
 Serial.println("BLINKING - Object detected!");
 } else {
 digitalWrite(ledPin, LOW); // Ensure LED is OFF
 }
 }

I compiled and uploaded the code to see how the ultrasonic sensor with Led reacts or communicate with my board with the code which is attached above.