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/*
Description: Transmits Arduino Nano 33 BLE Sense sensor readings over BLE,
including temperature, humidity, barometric pressure, and color,
using the Bluetooth Generic Attribute Profile (GATT) Specification
Author: Gary Stafford
Reference: Source code adapted from `Nano 33 BLE Sense Getting Started`
Adapted from Arduino BatteryMonitor example by Peter Milne
*/
/*
Generic Attribute Profile (GATT) Specifications
GATT Service: Environmental Sensing Service (ESS) Characteristics
Temperature
sint16 (decimalexponent -2)
Unit is in degrees Celsius with a resolution of 0.01 degrees Celsius
https://www.bluetooth.com/xml-viewer/?src=https://www.bluetooth.com/wp-content/uploads/Sitecore-Media-Library/Gatt/Xml/Characteristics/org.bluetooth.characteristic.temperature.xml
Humidity
uint16 (decimalexponent -2)
Unit is in percent with a resolution of 0.01 percent
https://www.bluetooth.com/xml-viewer/?src=https://www.bluetooth.com/wp-content/uploads/Sitecore-Media-Library/Gatt/Xml/Characteristics/org.bluetooth.characteristic.humidity.xml
Barometric Pressure
uint32 (decimalexponent -1)
Unit is in pascals with a resolution of 0.1 Pa
https://www.bluetooth.com/xml-viewer/?src=https://www.bluetooth.com/wp-content/uploads/Sitecore-Media-Library/Gatt/Xml/Characteristics/org.bluetooth.characteristic.pressure.xml
*/
#include <ArduinoBLE.h>
#include <Arduino_HTS221.h>
#include <Arduino_LPS22HB.h>
#include <Arduino_APDS9960.h>
const int UPDATE_FREQUENCY = 2000; // Update frequency in ms
const float CALIBRATION_FACTOR = -4.0; // Temperature calibration factor (Celsius)
int previousTemperature = 0;
unsigned int previousHumidity = 0;
unsigned int previousPressure = 0;
String previousColor = "";
int r, g, b, a;
long previousMillis = 0; // last time readings were checked, in ms
BLEService environmentService("181A"); // Standard Environmental Sensing service
BLEIntCharacteristic tempCharacteristic("2A6E", // Standard 16-bit Temperature characteristic
BLERead | BLENotify); // Remote clients can read and get updates
BLEUnsignedIntCharacteristic humidCharacteristic("2A6F", // Unsigned 16-bit Humidity characteristic
BLERead | BLENotify);
BLEUnsignedIntCharacteristic pressureCharacteristic("2A6D", // Unsigned 32-bit Pressure characteristic
BLERead | BLENotify); // Remote clients can read and get updates
BLECharacteristic colorCharacteristic("936b6a25-e503-4f7c-9349-bcc76c22b8c3", // Custom Characteristics
BLERead | BLENotify, 24); // 1234,5678,
BLEDescriptor colorLabelDescriptor("2901", "16-bit ints: r, g, b, a");
void setup() {
Serial.begin(9600); // Initialize serial communication
// while (!Serial); // only when connected to laptop
if (!HTS.begin()) { // Initialize HTS221 sensor
Serial.println("Failed to initialize humidity temperature sensor!");
while (1);
}
if (!BARO.begin()) { // Initialize LPS22HB sensor
Serial.println("Failed to initialize pressure sensor!");
while (1);
}
// Avoid bad readings to start bug
// https://forum.arduino.cc/index.php?topic=660360.0
BARO.readPressure();
delay(1000);
if (!APDS.begin()) { // Initialize APDS9960 sensor
Serial.println("Failed to initialize color sensor!");
while (1);
}
pinMode(LED_BUILTIN, OUTPUT); // Initialize the built-in LED pin
if (!BLE.begin()) { // Initialize NINA B306 BLE
Serial.println("starting BLE failed!");
while (1);
}
BLE.setLocalName("ArduinoNano33BLESense"); // Set name for connection
BLE.setAdvertisedService(environmentService); // Advertise environment service
environmentService.addCharacteristic(tempCharacteristic); // Add temperature characteristic
environmentService.addCharacteristic(humidCharacteristic); // Add humidity characteristic
environmentService.addCharacteristic(pressureCharacteristic); // Add pressure characteristic
environmentService.addCharacteristic(colorCharacteristic); // Add color characteristic
colorCharacteristic.addDescriptor(colorLabelDescriptor); // Add color characteristic descriptor
BLE.addService(environmentService); // Add environment service
tempCharacteristic.setValue(0); // Set initial temperature value
humidCharacteristic.setValue(0); // Set initial humidity value
pressureCharacteristic.setValue(0); // Set initial pressure value
colorCharacteristic.setValue(""); // Set initial color value
BLE.advertise(); // Start advertising
Serial.print("Peripheral device MAC: ");
Serial.println(BLE.address());
Serial.println("Waiting for connections...");
}
void loop() {
BLEDevice central = BLE.central(); // Wait for a BLE central to connect
// If central is connected to peripheral
if (central) {
Serial.print("Connected to central MAC: ");
Serial.println(central.address()); // Central's BT address:
digitalWrite(LED_BUILTIN, HIGH); // Turn on the LED to indicate the connection
while (central.connected()) {
long currentMillis = millis();
// After UPDATE_FREQUENCY ms have passed, check temperature & humidity
if (currentMillis - previousMillis >= UPDATE_FREQUENCY) {
previousMillis = currentMillis;
updateReadings();
}
}
digitalWrite(LED_BUILTIN, LOW); // When the central disconnects, turn off the LED
Serial.print("Disconnected from central MAC: ");
Serial.println(central.address());
}
}
int getTemperature(float calibration) {
// Get calibrated temperature as signed 16-bit int for BLE characteristic
return (int) (HTS.readTemperature() * 100) + (int) (calibration * 100);
}
unsigned int getHumidity() {
// Get humidity as unsigned 16-bit int for BLE characteristic
return (unsigned int) (HTS.readHumidity() * 100);
}
unsigned int getPressure() {
// Get humidity as unsigned 32-bit int for BLE characteristic
return (unsigned int) (BARO.readPressure() * 1000 * 10);
}
void getColor() {
// check if a color reading is available
while (!APDS.colorAvailable()) {
delay(5);
}
// Get color as (4) unsigned 16-bit ints
int tmp_r, tmp_g, tmp_b, tmp_a;
APDS.readColor(tmp_r, tmp_g, tmp_b, tmp_a);
r = tmp_r;
g = tmp_g;
b = tmp_b;
a = tmp_a;
}
void updateReadings() {
int temperature = getTemperature(CALIBRATION_FACTOR);
unsigned int humidity = getHumidity();
unsigned int pressure = getPressure();
getColor();
if (temperature != previousTemperature) { // If reading has changed
Serial.print("Temperature: ");
Serial.println(temperature);
tempCharacteristic.writeValue(temperature); // Update characteristic
previousTemperature = temperature; // Save value
}
if (humidity != previousHumidity) { // If reading has changed
Serial.print("Humidity: ");
Serial.println(humidity);
humidCharacteristic.writeValue(humidity);
previousHumidity = humidity;
}
if (pressure != previousPressure) { // If reading has changed
Serial.print("Pressure: ");
Serial.println(pressure);
pressureCharacteristic.writeValue(pressure);
previousPressure = pressure;
}
// Get color reading everytime
// e.g. "12345,45678,89012,23456"
String stringColor = "";
stringColor += r;
stringColor += ",";
stringColor += g;
stringColor += ",";
stringColor += b;
stringColor += ",";
stringColor += a;
if (stringColor != previousColor) { // If reading has changed
byte bytes[stringColor.length() + 1];
stringColor.getBytes(bytes, stringColor.length() + 1);
Serial.print("r, g, b, a: ");
Serial.println(stringColor);
colorCharacteristic.writeValue(bytes, sizeof(bytes));
previousColor = stringColor;
}
}
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