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Learn how to interface with digital sensors using I2C and other protocols in the Kinematrix sensor framework.

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I2C Environmental Sensors

Digital sensors like BME680, BME280, and other I2C devices provide high-precision measurements through a simple two-wire interface.

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BME680 (I2C)

The BME680 communicates over I2C and supports multiple sensors on the same bus using different addresses.
1

Hardware Setup

Connect the BME680 using I2C:
BME680    ESP32/Arduino
------    -------------
VCC   ->  3.3V
GND   ->  GND
SCL   ->  SCL (GPIO 22 on ESP32)
SDA   ->  SDA (GPIO 21 on ESP32)
2

Basic I2C Sensor

#define ENABLE_SENSOR_MODULE_V2
#define ENABLE_SENSOR_BME680_V2
#define ENABLE_SENSOR_UTILITY_V2
#include "Kinematrix.h"

BME680SensV2 bme680Sensor;  // Default I2C address 0x76

void setup() {
    Serial.begin(115200);
    
    JsonDocument doc;
    bme680Sensor.setDocumentValue(&doc);
    bme680Sensor.setDocument("bme680");
    
    if (bme680Sensor.init()) {
        Serial.println("BME680 initialized successfully");
    } else {
        Serial.println("BME680 initialization failed!");
    }
}

void loop() {
    if (bme680Sensor.update()) {
        Serial.print("Temperature: ");
        Serial.print((float)bme680Sensor.getFloatValue("temperature"));
        Serial.print("°C, Humidity: ");
        Serial.print((float)bme680Sensor.getFloatValue("humidity"));
        Serial.print("%, Pressure: ");
        Serial.print((float)bme680Sensor.getFloatValue("pressure"));
        Serial.print(" hPa, Gas: ");
        Serial.print((float)bme680Sensor.getFloatValue("gas"));
        Serial.println(" Ohms");
    }
    
    delay(2000);
}
3

Multiple I2C Sensors

Use different I2C addresses for multiple sensors on the same bus:
BME680SensV2* indoor = new BME680SensV2();      // Default: 0x76
BME680SensV2* outdoor = new BME680SensV2(0x77); // Alternate address

sensorModule.addSensor("indoor", indoor);
sensorModule.addSensor("outdoor", outdoor);
Source: /home/daytona/workspace/source/example/sensors/SensorModuleV2/SensorList/BME680SensV2/BasicBME680Sensor/BasicBME680Sensor.ino:1

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DHT Digital Sensors

DHT sensors use a single-wire digital protocol for temperature and humidity readings.

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DHT22/DHT11 Setup

#define ENABLE_SENSOR_MODULE_V2
#define ENABLE_SENSOR_DHT_V2
#define ENABLE_SENSOR_UTILITY_V2
#include "Kinematrix.h"

DHTSensV2 dhtSensor(2, DHT22);  // GPIO 2, DHT22 type

void setup() {
    Serial.begin(115200);
    
    JsonDocument doc;
    dhtSensor.setDocumentValue(&doc);
    dhtSensor.setDocument("dht");
    
    if (dhtSensor.init()) {
        Serial.println("DHT sensor initialized successfully");
    }
}

void loop() {
    if (dhtSensor.update()) {
        Serial.print("Temperature: ");
        Serial.print((float)dhtSensor.getFloatValue("temperature"));
        Serial.print("°C, Humidity: ");
        Serial.print((float)dhtSensor.getFloatValue("humidity"));
        Serial.print("%, Heat Index: ");
        Serial.print((float)dhtSensor.getFloatValue("heatIndex"));
        Serial.println("°C");
    }
    
    delay(2000);
}
Source: /home/daytona/workspace/source/example/sensors/SensorModuleV2/SensorList/DHTSensV2/BasicDHTSensor/BasicDHTSensor.ino:1

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DHT Sensor Types

  • DHT11: Lower accuracy (±2°C, ±5% RH), 1Hz sampling
  • DHT22: Higher accuracy (±0.5°C, ±2% RH), 0.5Hz sampling
DHTSensV2 dht11Sensor(3, DHT11);   // DHT11 on GPIO 3
DHTSensV2 dht22Sensor(4, DHT22);   // DHT22 on GPIO 4

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RTC and Time-Based Sensors

Real-time clock sensors maintain accurate time and date: 
#define ENABLE_SENSOR_MODULE_V2
#define ENABLE_SENSOR_RTC_DS3231_V2
#define ENABLE_SENSOR_UTILITY_V2
#include "Kinematrix.h"

SensorModuleV2 sensorModule;

void setup() {
    Serial.begin(115200);
    
    sensorModule.addSensor("rtc", new RTCDS3231SensV2());
    sensorModule.init();
    
    // Enable temperature reading from RTC
    RTCDS3231SensV2* rtc = (RTCDS3231SensV2*)sensorModule.getSensorByName("rtc");
    if (rtc) {
        rtc->enableTemperature(true);
    }
}

void loop() {
    sensorModule.update();
    
    if (sensorModule.isUpdated("rtc")) {
        Serial.print("Time: ");
        Serial.print((int)sensorModule["rtc"]["hour"]);
        Serial.print(":");
        Serial.print((int)sensorModule["rtc"]["minute"]);
        Serial.print(":");
        Serial.println((int)sensorModule["rtc"]["second"]);
    }
    
    delay(1000);
}

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Calibration for Digital Sensors

Even digital sensors can benefit from calibration: 
#define ENABLE_SENSOR_MODULE_V2
#define ENABLE_SENSOR_CALIBRATION_MODULE_V2
#define ENABLE_SENSOR_DHT_V2
#include "Kinematrix.h"

SensorCalibrationModuleV2 calibrationModule;

void setup() {
    Serial.begin(115200);
    
    calibrationModule.addSensor("dht22", new DHTSensV2(2, DHT22));
    calibrationModule.addSensor("dht11", new DHTSensV2(3, DHT11));
    calibrationModule.init();
    
    // Add calibration entries
    calibrationModule.addCalibrationEntry("dht22", "temperature");
    calibrationModule.addCalibrationEntry("dht11", "temperature");
    calibrationModule.addCalibrationEntry("dht22", "humidity");
    calibrationModule.addCalibrationEntry("dht11", "humidity");
    
    // Two-point calibration against reference sensors
    calibrationModule.calibrateTwoPoint("dht22", "temperature", 20.0, 19.8, 30.0, 30.3);
    calibrationModule.calibrateTwoPoint("dht11", "temperature", 20.0, 19.8, 30.0, 30.3);
    
    // One-point humidity calibration
    calibrationModule.calibrateOnePoint("dht22", "humidity", 60.0);
    calibrationModule.calibrateOnePoint("dht11", "humidity", 60.0);
    
    Serial.println("DHT sensors with calibration ready");
}

void loop() {
    calibrationModule.update();
    
    if (calibrationModule.isUpdated("dht22")) {
        float rawTemp = calibrationModule["dht22"]["temperature"];
        float calTemp = calibrationModule.getCalibratedValue("dht22", "temperature");
        float rawHum = calibrationModule["dht22"]["humidity"];
        float calHum = calibrationModule.getCalibratedValue("dht22", "humidity");
        
        Serial.println("=== DHT22 ===");
        Serial.print("Temp - Raw: ");
        Serial.print(rawTemp);
        Serial.print("°C, Cal: ");
        Serial.print(calTemp);
        Serial.println("°C");
        Serial.print("Humidity - Raw: ");
        Serial.print(rawHum);
        Serial.print("%, Cal: ");
        Serial.print(calHum);
        Serial.println("%");
    }
    
    delay(3000);
}
Source: /home/daytona/workspace/source/example/sensors/SensorModuleV2/SensorList/DHTSensV2/DHTWithCalibration/DHTWithCalibration.ino:1

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I2C Scanner Utility

Find connected I2C devices and their addresses: 
#include <Wire.h>

void setup() {
    Serial.begin(115200);
    Wire.begin();
    
    Serial.println("I2C Scanner");
    for (byte address = 1; address < 127; address++) {
        Wire.beginTransmission(address);
        byte error = Wire.endTransmission();
        
        if (error == 0) {
            Serial.print("I2C device found at address 0x");
            if (address < 16) Serial.print("0");
            Serial.println(address, HEX);
        }
    }
    Serial.println("Scan complete");
}

void loop() {}

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Common I2C Addresses

SensorDefault AddressAlternate Address
BME6800x760x77
BME2800x760x77
DS3231 RTC0x68-
MLX906140x5AConfigurable
INA2190x400x41-0x4F

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Wiring Diagrams

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I2C Bus (Multiple Sensors)

                3.3V
                 |
            4.7kΩ  4.7kΩ (pull-up resistors)
                 |   |
    ESP32/Arduino    |   |
         SDA --------+---+--- SDA (All sensors)
         SCL ------------+--- SCL (All sensors)
         GND ------------+--- GND (All sensors)
        3.3V ------------+--- VCC (All sensors)

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DHT22 Single-Wire Digital

DHT22     ESP32/Arduino
-----     -------------
VCC   ->  3.3V or 5V
DATA  ->  GPIO 2 (with 10kΩ pull-up to VCC)
NC    ->  Not connected
GND   ->  GND

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Troubleshooting

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I2C Communication Fails

  • Check pull-up resistors (4.7kΩ recommended)
  • Verify correct I2C address
  • Use I2C scanner to detect devices
  • Check wire length (keep short, < 1m)
  • Verify 3.3V logic levels

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DHT Sensor Returns NaN

  • Check pull-up resistor (10kΩ required)
  • Increase delay between readings (min 2 seconds)
  • Verify correct sensor type (DHT11 vs DHT22)
  • Check power supply stability

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Next Steps

Analog Sensors

Learn about analog sensor interfaces

Multi-Sensor Systems

Build systems combining multiple sensor types

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