Bluetooth LE

ITP | Week 2 | February 3, 2017

Don Coleman

Lightbulb Service - FF10

Advertising

Connect

Read Value

Write Value

Write Command

Heart Rate Service - 180d

Notification

Indication

Peripheral

Provides services

Central

Uses services on a peripheral

Today we'll build peripherals that

• Control a LED
• Send button state
• Send temperature data

Arduino 101 - CurieBLE

Arduino BLE Peripheral

CurieBLE / Arduino 101

#include <CurieBLE.h>
  

BLEPeripheral library

#include <BLEPeripheral.h>
  

Exercise 1

Blink

Blink.ino

#define LED_PIN 6

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);   // turn the LED on
  delay(1000);                   // wait one second
  digitalWrite(LED_PIN, LOW);    // turn the LED off
  delay(1000);                   // wait one second
}
                

Exercise 2

Bluetooth LED

Lightbulb Service - FF10

LED.ino

  #include <CurieBLE.h>

  #define LED_PIN  6
	

Create Service

BLEService ledService = BLEService("FF10");
	

Characteristic & Descriptor

BLECharCharacteristic switchCharacteristic
  = BLECharCharacteristic("FF11", BLERead | BLEWrite);
BLEDescriptor switchDescriptor
  = BLEDescriptor("2901", "Switch");
	

Setup

void setup() {
  Serial.begin(9600);
  pinMode(LED_PIN, OUTPUT);

  blePeripheral.addAttribute(ledService);
  blePeripheral.addAttribute(switchCharacteristic);
  blePeripheral.addAttribute(switchDescriptor);
  // ...
}
	

Setup

void setup() {
  // ...
  switchCharacteristic.setEventHandler(
              BLEWritten, switchCharacteristicWritten);

  blePeripheral.setAdvertisedServiceUuid(
                                    ledService.uuid());
  blePeripheral.setLocalName("LED");
  blePeripheral.begin();
}
	

Loop

  void loop() {
    blePeripheral.poll();
  }
	

Switch Characteristic Written

void switchCharacteristicWritten(
	  BLECentral& central,
	  BLECharacteristic& characteristic) {

  if (switchCharacteristic.value()) {
    Serial.println(F("LED on"));
    digitalWrite(LED_PIN, HIGH);
  } else {
    Serial.println(F("LED off"));
    digitalWrite(LED_PIN, LOW);
  }
}
	

Local Name vs Device Name

What is the difference?

void setup() {
  // In Advertising Data 0x09
  blePeripheral.setLocalName("LOCAL NAME");

  // Generic Access Service 0x1800, 0x2A00
  blePeripheral.setDeviceName("DEVICE NAME");

  // ...
}
                

Local Name is 0x09 in Advertising Data

The Generic Access Service 0x1800 contains
the Device Name Characteristic 0x2A00

Exercise 3

Dimmable LED

Lightbulb Service - FF10

Characteristic & Descriptor

BLEUnsignedCharCharacteristic dimmerCharacteristic
 = BLEUnsignedCharCharacteristic("FF12",
                                 BLERead | BLEWrite);
BLEDescriptor dimmerDescriptor
 = BLEDescriptor("2901", "Dimmer");
	

Setup

void setup() {
  // ...
  blePeripheral.addAttribute(dimmerCharacteristic);
  blePeripheral.addAttribute(dimmerDescriptor);
  // ...
  dimmerCharacteristic.setEventHandler(
              BLEWritten, dimmerCharacteristicWritten);
  // ...
}

Dimmer Characteristic Written

void dimmerCharacteristicWritten(
	  BLECentral& central,
	  BLECharacteristic& characteristic) {
  Serial.print(F("Dimmer set to: "));
  Serial.println(dimmerCharacteristic.value());

  analogWrite(LED_PIN, dimmerCharacteristic.value());
}
	

Exercise 4

Button

Button Service - FFE0

Service, Characteristic, & Descriptor

 BLEService buttonService = BLEService("FFE0");

 BLECharCharacteristic buttonCharacteristic =
        BLECharCharacteristic("FFE1", BLENotify);

 BLEDescriptor buttonDescriptor =
        BLEDescriptor("2901", "Button State");
                

Loop

void loop() {
  blePeripheral.poll();
  char buttonValue = digitalRead(BUTTON_PIN);

  if (buttonCharacteristic.value() != buttonValue) {
    Serial.print("Button ");
    Serial.println(buttonValue, HEX);
    buttonCharacteristic.setValue(buttonValue);
  }
}
                

Button v2

Limit Button Read

void loop() {
  blePeripheral.poll();

  // limit how often we read the button
  if (millis() - lastReadTime > readInterval) {
    readButton();
    lastReadTime = millis();
  }
}
                

Read Button

void readButton() {
  char buttonValue = digitalRead(BUTTON_PIN);

  // has the value changed since the last read?
  if (buttonCharacteristic.value() != buttonValue) {
    Serial.print("Button ");
    Serial.println(buttonValue, HEX);
    buttonCharacteristic.setValue(buttonValue);
  }
}
                

Exercise 5

Thermometer

Thermometer Service - 0xBBB0

Service, Characteristic, & Descriptor

  BLEService thermometerService = BLEService("BBB0");
  BLEFloatCharacteristic temperatureCharacteristic
      = BLEFloatCharacteristic("BBB1",
                               BLERead | BLENotify);
  BLEDescriptor temperatureDescriptor
      = BLEDescriptor("2901", "degrees C");
            	

Loop

void loop()
{
  blePeripheral.poll();

  if(millis() - previousMillis > interval) {
    pollTemperatureSensor();
    previousMillis = millis();
  }
}

Poll Temperature Sensor

void pollTemperatureSensor()
{
  float temp = calculateTemperature();

  if (tempCharac.value() != temp) {
    tempCharac.setValue(temp);
    Serial.println(temp);
  }
}

Calculate Temperature

float calculateTemperature()
{
  // read the sensor value
  int sensorValue = analogRead(TEMPERATURE_PIN);

  // 3.3V logic, 10-bit ADC
  float voltage = sensorValue * 3.3 / 1024.0;
  // 100 degrees per volt with 0.5 volt offset
  float temperature = (voltage - 0.5) * 100;

  return temperature;
}

Don Coleman

http://don.github.io/slides/

NYU ITP Bluetooth Spring 2017 Week 2 by Don Coleman is licensed under a Creative Commons Attribution 4.0 International License.