Week 9: Input Devices¶

Week 9 Assignment:

Group Assignment
1. Probe an input device’s analog levels and digital signals
Individual Assignment
1. Measure something: add a sensor to a microcontroller board that you have designed and read it

Notes from the Lecture

they are multiple ways to get input in:
- ports / pins
- comparator -> the one who will told you voltage is higher or lower. you can do it quickly
- A/D (Analog to Digital converter) -> give you a voltage and give you the number
- I2C -> digital protocol we use, digital signal
READ THE DATA SHEET to know what the hardware actually does

GROUP ASSIGNMENT¶

An Input Device’s Analog Levels and Digital Signals¶

INDIVIDUAL ASSIGNMENT¶

The input devices cardboard at Chaihuo Makers Space contains various modules, most of which are from Seeed’s Grove system.

This week, I experimented with different kinds of input devices, including a temperature sensor, touch sensor, mechanical keypad, thumb joystick, PIR motion sensor and RTC (Real-Time Clock).

For all the experiments, I used the XIAO ESP32C3 as the microcontroller.

Since all of the input devices are part of Seeed’s Grove ecosystem, I used the Grove Base for XIAO as an expansion board. This board acts as a bridge between the Seeed Studio XIAO and the Grove modules.

Grove Base for XIAO Information:

Feature:

On-board Lithium Battery Charging and Management Function
Grove connectors ( Grove IIC x 2, Grove UART x 1 ), all 14 GPIO led out
Compact and Breakable Design
Flash SPI Bonding Pad Reserved
On-board Power Switch and Charging Status Indicator Light

Specifications:

Item	Value
Operating Voltage	3.3V / 3.7V Lithium Battery
Load Capacity	800mA
Charging Current	400mA (Max)
Operating Temperature	- 40°C to 85°C
Storage Temperature	-55°C to 150°C
Grove Interface	I2C 2 / UART 1

For programming, I used the Arduino IDE.

1. Temperature Sensor¶

Prepare the materials needed:
- XIAO ESP32C3
- Grove Base for XIAO
- Grove - Temperature Sensor V1.2
Grove - Temperature Sensor V1.2:

This temperature sensor measures ambient temperature (the temperature of the surrounding environment) using a thermistor. It operates within a range of −40 to 125 °C and has an accuracy of ±1.5 °C.

Specifications:

Item Value

Voltage 3.3V ~ 5V

Zero Power Resistance 100 KΩ

Resistance Tolerance ±1%

Operating Temperature Range -40 ~ +125 ℃

Nominal B-Constant 4250 ~ 4299K
Connect Grove - Temperature Sensor to port A0 of Grove Base
Plug XIAO ESP32C3 to Grove Base
Connect XIAO ESP32C3 to PC via a USB-C cable

Copy the following code into Arduino IDE and upload the code:

#include <math.h>

const int B = 4275000;            // B value of the thermistor
const int R0 = 100000;            // R0 = 100k
const int pinTempSensor = A0;     // Grove Temperature Sensor on A0

float filteredTemp = 0;

// Read averaged ADC value
float readADC(int pin) {
long sum = 0;
const int samples = 20;

for (int i = 0; i < samples; i++) {
    sum += analogRead(pin);
    delay(5);
}

return sum / (float)samples;
}

void setup() {
Serial.begin(115200);
delay(1000);

analogSetPinAttenuation(pinTempSensor, ADC_11db); // improve range
}

void loop() {
float a = readADC(pinTempSensor);

// Convert ADC to resistance
float R = R0 * (4095.0 / a - 1.0);

// Convert resistance to temperature
float temperature = 1.0 / (log(R / R0) / B + 1 / 298.15) - 273.15;

// Smooth output (low-pass filter)
if (filteredTemp == 0) {
    filteredTemp = temperature; // initialize
} else {
    filteredTemp = 0.85 * filteredTemp + 0.15 * temperature;
}

// Output
Serial.print("Raw Temp: ");
Serial.print(temperature, 3);

Serial.print(" | Filtered Temp: ");
Serial.println(filteredTemp, 3);

delay(200);
}

Open the Serial Monitor in the Arduino IDE by clicking Tools -> Serial Monitor. You should see results in the Serial Monitor, as shown below.

It is shown that the temperature at that time is 25°C.

2. Touch Sensor¶

Prepare the materials needed:

XIAO ESP32C3
Grove Base for XIAO
Grove - LED Socket & LED
Grove - Touch Sensor

Grove - Touch Sensor:

This sensor enables touch-based input by sensing capacitance changes caused by a nearby finger.

Specifications:

Item	Value
Operating Voltage	2.0V - 5.5V
Operating Current(Vcc=3V)	1.5 - 3.0μA
Operating Current(VDD=3V)	3.5 - 7.0μA
Output Response Time	60 - 220ms
Used Chipset	TTP223-BA6
Interface	Digital Port

Connect Grove - Touch Sensor to port D0 and Grove LED Socket to port D1 of Grove Base
Plug XIAO ESP32C3 to Grove Base
Connect XIAO ESP32C3 to PC via a USB-C cable

Copy the following code into Arduino IDE and upload the code:

const int TouchPin = D0;
const int ledPin   = D1;

void setup() {
    pinMode(TouchPin, INPUT);
    pinMode(ledPin, OUTPUT);
}

void loop() {
    int sensorValue = digitalRead(TouchPin);

    if (sensorValue == HIGH) {
        digitalWrite(ledPin, HIGH);
    } else {
        digitalWrite(ledPin, LOW);
    }
}

6. The LED turns on when we place our finger near the sensor, and it turns off when we move our finger away.

Turn off - finger awayTurn on - finger nearby

3. Mech Keypad¶

Prepare the materials needed:
- XIAO ESP32C3
- Grove Base for XIAO
- Grove - LED Socket & LED
- Grove - Mech Keycap
Grove - Mech Keypad:

A mechanical switch with a build-in LED

Features
- Programmable LED
- Reliable mechanical structure
- Extremely long operating Life
Specifications:

Item Value

Operating Voltage 3.0V - 5.0V

Insulation Resistance 100MΩ Min

Contract Resistance 200 mΩ Max

Operating Life without Load 20,000,000 times press
Connect Grove - Mech Keypad to port D0 and Grove LED Socket to port D1 of Grove Base
Plug XIAO ESP32C3 to Grove Base
Connect XIAO ESP32C3 to PC via a USB-C cable

Copy the following code into Arduino IDE and upload the code:

This code is generated from ChatGPT

const int buttonPin = D0;
const int ledPin    = D1;

bool ledState = false;      // current LED state
bool lastButtonState = HIGH;
bool currentButtonState;

void setup() {
    pinMode(buttonPin, INPUT);
    pinMode(ledPin, OUTPUT);
}

void loop() {
    currentButtonState = digitalRead(buttonPin);

    // Detect button press (HIGH → LOW transition)
    if (lastButtonState == HIGH && currentButtonState == LOW) {
        ledState = !ledState;  // toggle LED
        digitalWrite(ledPin, ledState ? HIGH : LOW);
    }

    lastButtonState = currentButtonState;

    delay(50); // simple debounce
}

6. Toggle switch LED on and off

Turn offTurn on

4. Thumb Joystick¶

Prepare the materials needed:
- XIAO ESP32C3
- Grove Base for XIAO
- Grove - Thumb Joystick
Grove - Thumb Joystick

Grove Thumb Joystick uses two approximately 10k potentiometers for the X and Y axes, allowing it to detect movement in two dimensions by producing analog signals.

Specifications:

Item Min Typical Max Unit

Working Voltage 4.75 5.0 5.25 V

Output Analog Value (X-Coordinate) 206 516 798 \

Output Analog Value (Y-Coordinate) 203 507 797 \
Connect Grove - Thumb Joystick to the A0/A1 of Grove Base by using the 4-pin grove cable
Plug XIAO ESP32C3 to Grove Base
Connect XIAO ESP32C3 to PC via a USB-C cable

Copy the following code into Arduino IDE and upload the code:

This code is generated from ChatGPT

/*
Thumb Joystick demo for XIAO ESP32C3
Grove Thumb Joystick connected to A0 & A1
*/

const int pinX = 2;  // A0 → GPIO2
const int pinY = 3;  // A1 → GPIO3

void setup()
{
    Serial.begin(115200);

    // Optional: set ADC resolution (default is 12-bit)
    analogReadResolution(12);
}

void loop()
{
    int sensorValue1 = analogRead(pinX);
    int sensorValue2 = analogRead(pinY);

    Serial.print("X: ");
    Serial.print(sensorValue1);
    Serial.print("  Y: ");
    Serial.println(sensorValue2);

    delay(200);
}

When we move the joystick, we can see the X and Y values change in the Serial Monitor.

5. PIR Motion Sensor¶

Prepare the materials needed:

XIAO ESP32C3
Grove Base for XIAO
Grove - PIR Motion Sensor

Grove - PIR Motion Sensor

This sensor is designed to detect movement, typically from human movement.

Features:

Grove compatible interface
Adjustable detecting distance
Adjustable holding time

Specifications:

Item	Value
Operating Voltage	3V–5V
Operating Current(VCC = 3V)	100uA
Operating Current(VCC = 5V)	150uA
Measuring Range	0.1 - 6m
Default detecting distance	3m
Holding Time	1 - 25s
Working Wave Length	7 - 14um
Detecting Angle	120 degrees

Connect Grove - PIR Motion Sensor to port D2 of Grove Base
Plug XIAO ESP32C3 to Grove Base
Connect XIAO ESP32C3 to PC via a USB-C cable

Copy the following code into Arduino IDE and upload the code:

This code is generated from ChatGPT

#define PIR_MOTION_SENSOR D2  // 👈 use a Grove digital port

int lastState = LOW;

void setup()
{
    pinMode(PIR_MOTION_SENSOR, INPUT);
    Serial.begin(115200);
}

void loop()
{
    int currentState = digitalRead(PIR_MOTION_SENSOR);

    if (currentState != lastState)
    {
        if (currentState == HIGH)
        {
            Serial.println("🚶 Motion detected!");
        }
        else
        {
            Serial.println("👀 Motion ended");
        }

        lastState = currentState;
    }

    delay(50);
}

6. If motion just started -> “🚶 Motion detected!”, if motion just stopped -> “👀 Motion ended”

6. RTC (Real Time Clock)¶

Prepare the materials needed:

XIAO ESP32C3
Grove Base for XIAO
Grove - RTC

Grove - RTC

This module supports I2C and uses R1225 battery to keep accurate time (including leap years) in 12- or 24-hour format up to the year 2100.

Specifications:

Item	Value
PCB Size	2.0cm*4.0cm
Interface	2.0mm pitch pin header
IO Structure	SCL, SDA, VCC, GND
ROHS	YES
VCC	3.3 ~ 5.5V
Logic High Level Input	2.2 ~ VCC+0.3 V
Logic Low Level Input	-0.3 ~ +0.8 V
Battery Voltage	2.0~3.5 V

Connect Grove - RTC to port I2C of Grove Base
Plug XIAO ESP32C3 to Grove Base
Connect XIAO ESP32C3 to PC via a USB-C cable
Download the RTC Library
Open Arduino IDE. Click on Sketch -> Include Library -> Add .ZIP Library
Check if the library install correctly. Click on File -> Examples -> Grove - RTC DS1307 -> SetTimeAndDisplay

Copy the following code into Arduino IDE and upload the code:

This code is generated from ChatGPT

#include <Wire.h>
#include "DS1307.h"

#define SDA_PIN 6
#define SCL_PIN 7

DS1307 rtc;  // renamed from "clock" to "rtc"

void setup()
{
    Serial.begin(115200);

    Wire.begin(SDA_PIN, SCL_PIN);

    rtc.begin();

    // Set time once, then comment out
    rtc.fillByYMD(2026, 3, 20);
    rtc.fillByHMS(12, 0, 0);
    rtc.fillDayOfWeek(FRI);

    rtc.setTime();
}

void loop()
{
    printTime();
    delay(1000);
}

void printTime()
{
    rtc.getTime();

    Serial.print(rtc.hour, DEC);
    Serial.print(":");
    Serial.print(rtc.minute, DEC);
    Serial.print(":");
    Serial.print(rtc.second, DEC);
    Serial.print("  ");

    Serial.print(rtc.month, DEC);
    Serial.print("/");
    Serial.print(rtc.dayOfMonth, DEC);
    Serial.print("/");
    Serial.print(rtc.year + 2000, DEC);

    Serial.print("  ");

    switch (rtc.dayOfWeek)
    {
        case MON: Serial.print("MON"); break;
        case TUE: Serial.print("TUE"); break;
        case WED: Serial.print("WED"); break;
        case THU: Serial.print("THU"); break;
        case FRI: Serial.print("FRI"); break;
        case SAT: Serial.print("SAT"); break;
        case SUN: Serial.print("SUN"); break;
    }

    Serial.println();
}

9. In the Serial Monitor, we can see the time, date, and day:

Item	Value
Voltage	3.3V ~ 5V
Zero Power Resistance	100 KΩ
Resistance Tolerance	±1%
Operating Temperature Range	-40 ~ +125 ℃
Nominal B-Constant	4250 ~ 4299K

Item	Value
Operating Voltage	3.0V - 5.0V
Insulation Resistance	100MΩ Min
Contract Resistance	200 mΩ Max
Operating Life without Load	20,000,000 times press

Item	Min	Typical	Max	Unit
Working Voltage	4.75	5.0	5.25	V
Output Analog Value (X-Coordinate)	206	516	798	\
Output Analog Value (Y-Coordinate)	203	507	797	\