Bluetooth Weather Station: DHT Sensor testing

This Arduino code is a simple program to measure data from different sensors and display it on the Serial Monitor. It uses three sensors: DHT11 for temperature and humidity, and a light sensor connected to analog pin A0.

Let's break down the code step-by-step:

1. Libraries: The code includes the "DHT.h" library. This library allows communication with the DHT (Digital Humidity and Temperature) sensor.

2. DHT Sensor Configuration: The DHT sensor is defined using macros. DHTPIN is set to 7, which represents the digital pin to which the DHT sensor is connected. DHTTYPE is set to DHT11, indicating that we are using a DHT11 sensor. There are other types like DHT22 and DHT21 with higher accuracy but require different libraries.

3. DHT Instance: An instance of the DHT class is created named dht, using the DHTPIN and DHTTYPE configurations.

4. Setup Function: In the setup function, the Serial communication is initialized with a baud rate of 9600 (bits per second). The DHT sensor is also initialized using the dht.begin() function.

5. Loop Function: This is the main part of the code that runs in a loop repeatedly.

6. DHT Readings: The code reads the temperature and humidity values from the DHT sensor using the dht.readTemperature() and dht.readHumidity() functions, respectively. These values are stored in variables temperature and humidity.

7. Light Sensor Reading: The code reads the light sensor's analog value using the analogRead(A0) function. The value is then converted to a percentage representing the light level and stored in the light variable.

8. Serial Monitor Output: The code prints the temperature, humidity, and light level on the Serial Monitor. The Serial.print() function is used to display the values, and Serial.println() is used to move to the next line after each reading.

9. Delay: The code introduces a 500-millisecond delay using the delay(500) function before starting the next iteration of the loop. This delay allows time for the sensors to stabilize between readings and prevents excessive data updates on the Serial Monitor.

In summary, this Arduino code reads temperature and humidity from a DHT11 sensor and light level from an analog light sensor. It then displays these values on the Serial Monitor, providing a simple way to monitor the environmental conditions around the Arduino board.

 Creating the Arduino Sketch 

With confirmation that our sensors are functioning accurately, we are ready to compose the definitive sketch enabling communication between the Arduino board and the forthcoming Android application. Below is the comprehensive sketch for this phase:

// Control Arduino board from BLE

// Enable lightweight
#define LIGHTWEIGHT 1

// Libraries
#include <SPI.h>
#include "Adafruit_BLE_UART.h"
#include <aREST.h>
#include "DHT.h"

// Pins
#define ADAFRUITBLE_REQ 10
#define ADAFRUITBLE_RDY 2     // This should be an interrupt pin, on Uno thats #2 or #3
#define ADAFRUITBLE_RST 9

// DHT sensor
#define DHTPIN 7 
#define DHTTYPE DHT11

// DHT instance
DHT dht(DHTPIN, DHTTYPE);

// Create aREST instance
aREST rest = aREST();

// BLE instance
Adafruit_BLE_UART BTLEserial = Adafruit_BLE_UART(ADAFRUITBLE_REQ, ADAFRUITBLE_RDY, ADAFRUITBLE_RST);

// Variables to be exposed to the API
int temperature;
int humidity;
int light;

void setup(void)
{  
  // Start Serial
  Serial.begin(9600);

  // Start BLE
  BTLEserial.begin();
 
  // Give name and ID to device
  rest.set_id("001");
  rest.set_name("weather_station"); 
  
  // Expose variables to API
  rest.variable("temperature",&temperature);
  rest.variable("humidity",&humidity);
  rest.variable("light",&light);
  
   // Init DHT
  dht.begin();
  
  // Welcome message
  Serial.println("Weather station started");
}

void loop() {  
  
  // Measure from DHT
  float t = dht.readTemperature();
  float h = dht.readHumidity();
  temperature = (int)t;
  humidity = (int)h;

  // Measure light level
  float sensor_reading = analogRead(A0);
  light = (int)(sensor_reading/1024*100);
  
  // Tell the nRF8001 to do whatever it should be working on.
  BTLEserial.pollACI();
  
  // Ask what is our current status
  aci_evt_opcode_t status = BTLEserial.getState();
  
  // Handle REST calls
  if (status == ACI_EVT_CONNECTED) {
    rest.handle(BTLEserial);
  }
 }

This code is an Arduino sketch that allows the Arduino board to be controlled and accessed through Bluetooth Low Energy (BLE) using an Android application. The sketch is designed to create a weather station that measures temperature, humidity, and light levels and exposes these values through a REST API using the aREST library.