Bluetooth Low Energy: Gesture Control

Example of the use of Bluetooth Low Energy technology using the Arduino MKR WiFi 1010 and Arduino Nano 33 BLE Sense boards with the ArduinoBLE library.

This example is based on the “Central → LedControl” and “Peripherical → LED” sketches of the ArduinoBLE library.

The Bluetooth on the Arduino Nano 33 BLE Sense is managed by a NINA B306 module (Bluetooth v.5.0)

NINA B306 Data Sheet

The Bluetooth on the Arduino MKR WiFi 1010 is managed by the NINA-W102 module (Bluetooth v.4.2)

NINA-W10 Data Sheet

The following links explain the basics of Bluetooth Low Energy technology that will help us understand how it works:

https://www.arduino.cc/en/Reference/ArduinoBLE

https://learn.adafruit.com/introduction-to-bluetooth-low-energy/introduction

CIRCUIT

Components:

• Central device: Arduino Nano 33 BLE Sense.
• Peripheral device: Arduino MKR WiFi 1010 + Arduino MKR RGB Shield.

Target:

The central device will connect to the peripheral device searching for the characteristic of the specified service.

Once the connection is established if the Arduino Nano 33 BLE Sense gesture sensor (ADPS-9960) detects any of the following movements: UP, DOWN, LEFT and RIGHT the central device will write the corresponding value (associated with these movements) in the characteristic of the peripheral device by displaying the corresponding text with a color on the MKR RGB LED Matrix.

SKETCHES

A) Arduino Nano 33 BLE Sense central device sketch:

#include <ArduinoBLE.h>
#include <Arduino_APDS9960.h>
const char* deviceServiceUuid = "19b10000-e8f2-537e-4f6c-d104768a1214";
const char* deviceServiceCharacteristicUuid = "19b10001-e8f2-537e-4f6c-d104768a1214";
int gesture = -1; 
int oldGestureValue = -1;   
void setup() {
 Serial.begin(9600);
 while (!Serial);
 if (!APDS.begin()) {
   Serial.println("Error initializing APDS9960 sensor!");
 }
  APDS.setGestureSensitivity(80); // [1..100]
 // begin ble initialization
 if (!BLE.begin()) {
   Serial.println("starting BLE failed!");
   while (1);
 }
 Serial.println("BLE Central - gesture control");
}
void loop() {
    connectToPeripheral();
}
void connectToPeripheral(){
 BLEDevice peripheral;
 do
 {
    // start scanning for peripherals
   BLE.scanForUuid(deviceServiceUuid);
   peripheral = BLE.available();
 } while (!peripheral);
 if (peripheral) {
   // discovered a peripheral, print out address, local name, and advertised service
   Serial.print("Found  ");
   Serial.print(peripheral.address());
   Serial.print(" '");
   Serial.print(peripheral.localName());
   Serial.print("' ");
   Serial.print(peripheral.advertisedServiceUuid());
   Serial.println();
   // stop scanning
   BLE.stopScan();
   controlPeripheral(peripheral);
 }
}
void controlPeripheral(BLEDevice peripheral) {
 // connect to the peripheral
 Serial.println("Connecting ...");
 if (peripheral.connect()) {
   Serial.println("Connected");
 } else {
   Serial.println("Failed to connect!");
   return;
 }
 // discover peripheral attributes
 Serial.println("Discovering attributes ...");
 if (peripheral.discoverAttributes()) {
   Serial.println("Attributes discovered");
 } else {
   Serial.println("Attribute discovery failed!");
   peripheral.disconnect();
   return;
 }
 BLECharacteristic gestureCharacteristic = peripheral.characteristic(deviceServiceCharacteristicUuid);
 if (!gestureCharacteristic) {
   Serial.println("Peripheral does not have gesture characteristic!");
   peripheral.disconnect();
   return;
 } else if (!gestureCharacteristic.canWrite()) {
   Serial.println("Peripheral does not have a writable gesture characteristic!");
   peripheral.disconnect();
   return;
 }
 while (peripheral.connected()) {
   gesture = gestureDetectection();
   if (oldGestureValue != gesture) {
     // gesture value changed
     oldGestureValue = gesture;
     Serial.print("writing value: ");
     Serial.println(gesture);
     gestureCharacteristic.writeValue((byte)gesture);
     Serial.println("done!");
   }
 }
 Serial.println("Peripheral disconnected!");
}
int gestureDetectection(){
 if (APDS.gestureAvailable()) {
   // a gesture was detected
   gesture = APDS.readGesture();
   switch (gesture) {
     case GESTURE_UP:
       Serial.println("Detected UP gesture");
       break;
     case GESTURE_DOWN:
       Serial.println("Detected DOWN gesture");
       break;
     case GESTURE_LEFT:
       Serial.println("Detected LEFT gesture");
       break;
     case GESTURE_RIGHT:
       Serial.println("Detected RIGHT gesture");
       break;
     default:
       Serial.println("NO gesture detected!");
       break;
     }
   }
   return gesture;
}

B) Arduino MKR WiFi 1010 peripheral device sketch:

#include <ArduinoBLE.h>
#include <Arduino_MKRRGB.h>
enum {
 GESTURE_NONE = -1,
 GESTURE_UP = 0,
 GESTURE_DOWN = 1,
 GESTURE_LEFT = 2,
 GESTURE_RIGHT = 3
};
const char* deviceServiceUuid = "19b10000-e8f2-537e-4f6c-d104768a1214";
const char* deviceServiceCharacteristicUuid = "19b10001-e8f2-537e-4f6c-d104768a1214";
int gesture = -1;
// BLE gesture Service
BLEService gestureService(deviceServiceUuid); 
// BLE gesture Switch Characteristic 
BLEByteCharacteristic gestureCharacteristic(deviceServiceCharacteristicUuid, BLERead | BLEWrite);
void setup() {
 //Serial.begin(9600);
 //while (!Serial);
 // initialize the display
 MATRIX.begin();
 // set the brightness, supported values are 0 - 255
 MATRIX.brightness(120);
 // configure the text scroll speed
 MATRIX.textScrollSpeed(50);
 MATRIX.clear();
 MATRIX.endDraw();
 // begin ble initialization
 if (!BLE.begin()) {
   //Serial.println("starting BLE failed!");
   while (1);
 }
 // set advertised local name and service UUID:
 BLE.setLocalName("Gesture peripheral");
 BLE.setAdvertisedService(gestureService);
 // add the characteristic to the service
 gestureService.addCharacteristic(gestureCharacteristic);
 // add service
 BLE.addService(gestureService);
 // set the initial value for the characeristic:
 gestureCharacteristic.writeValue(-1);
 // start advertising
 BLE.advertise();
 //Serial.println("BLE gesture Peripheral");
}
void loop() {
 // listen for BLE peripherals to connect:
 BLEDevice central = BLE.central();
 // if a central is connected to peripheral:
 if (central) {
   //Serial.print("Connected to central: ");
   // print the central's MAC address:
   //Serial.println(central.address());
   // while the central is still connected to peripheral:
   while (central.connected()) {
     // if the remote device wrote to the characteristic,
     if (gestureCharacteristic.written()) {
        gesture = gestureCharacteristic.value();
        writeGesture(gesture);
      }
   }
   // when the central disconnects, print it out:
   //Serial.print(F("Disconnected from central: "));
   //Serial.println(central.address());
 }
}
void writeGesture(int gesture)
{
 int R = 0;
 int G = 0;
 int B = 0;
 String text = "";
  switch (gesture) {
     case GESTURE_UP:
       text =" UP";
       R=0;
       G=255;
       B=0;
       break;
     case GESTURE_DOWN:
       text ="DOWN";
       R=255;
       G=0;
       B=0;
       break;
     case GESTURE_LEFT:
       text ="LEFT";
       R=0;
       G=0;
       B=255;
       break;
     case GESTURE_RIGHT:
       text ="RIGHT";
       R=207;
       G=9;
       B=227;
       break;
     default:
       text ="";
       R=0;
       G=0;
       B=0;
       break;
   }
   MATRIX.clear();
   MATRIX.endDraw();
   MATRIX.beginText(0, 0, R, G, B); // X, Y, then R, G, B
   MATRIX.print(text);
   MATRIX.endText(SCROLL_LEFT);
}