How to control Arduino using Bluetooth

In this upcoming chapter, we delve into the process of assembling components and creating our inaugural application for controlling an Arduino board using Bluetooth Low Energy (BLE). The rationale behind exclusively adopting BLE for our Bluetooth-oriented undertakings is its status as the cutting-edge communication standard during the book's publication period. Unlike earlier Bluetooth modules, BLE modules exhibit diminished energy consumption, owing to their burst-operating nature instead of maintaining a continuous connection. Moreover, BLE boasts minimal transmission delays and offers a range akin to that of its older Bluetooth counterparts.

Our focal point entails establishing a connection between a BLE module and an Arduino, coupled with an LED that we'll manage through an Android app. Subsequently, we'll craft an Arduino sketch employing the aREST library, facilitating the reception of Bluetooth-initiated commands from a smartphone or tablet. The Android application itself will empower remote control over the board, and we'll have the chance to elevate user interaction by assimilating buttons for toggling the LED's state.

Key takeaways from this chapter encompass:

• Establishing a linkage between a BLE module and an Arduino board
• Developing an Arduino sketch to facilitate Bluetooth communication on the Arduino platform
• Crafting an Android app to dispatch commands to the Arduino board via Bluetooth

You will require the following components for this project:

• An LED in a color of your preference
• A 330 Ohm resistor
• A breadboard
• Jumper wires

Here is a list of the hardware components along with web links for reference:

• Arduino Uno board: Link
• LEDs: Link
• 330 Ohm resistor: Link
• Adafruit nRF8001 breakout board: Link
• Breadboard: Link
• Jumper wires: Link

On the software side, you will need the following:

• Arduino IDE: Link
• Arduino aREST library: Link
• nRF8001 Arduino library for BLE chip: Link

To install a library, extract the folder into your Arduino /libraries directory or create the directory if it doesn't exist. To locate your Arduino folder or set a new one, access the Preferences option in the Arduino IDE.

Hardware Configuration: 

Now, let's proceed with building the hardware part of the project. For your convenience, here's a schematic of the project:

Below are the sequential steps we will carry out:

1. Begin by situating both the Bluetooth module and the LED onto the breadboard.

2. Proceed to establish the power connection between the Arduino board and the breadboard as follows: Connect the Arduino board's 5V to the red power rail, and its GND to the blue power rail.

3. Now, we will establish the connection for the BLE module. Initially, link the module's power supply: Attach GND to the blue power rail, and VIN to the red power rail.

4. Subsequently, establish connections for the Serial Peripheral Interface (SPI) communication wires: Connect SCK to Arduino pin 13, MISO to Arduino pin 12, and MOSI to Arduino pin 11.

5. Next, establish connections for the REQ pin to Arduino pin 10. Additionally, connect the RDY pin to Arduino pin 2, and the RST pin to Arduino pin 9.

6. Addressing the LED component, place a resistor on the breadboard in series with the LED. Connect the resistor to the LED's anode, which is the longer pin.

7. Connect the other end of the resistor to Arduino pin 7.

8. Lastly, connect the LED's cathode (the shorter pin) to the blue power rail, i.e., the ground.

The project's fully assembled configuration is depicted in the provided image.

 Writing the Arduino sketch

We will now write the Arduino sketch so that the Arduino board can talk with the BLE module and receive commands from Android via Bluetooth. Here is the complete sketch for this part:

 // Control Arduino board from BLE

// Enable lightweight mode
#define LIGHTWEIGHT 1

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

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

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

void setup(void)
{  
  // Start Serial
  Serial.begin(9600);
  Serial.println(F("Adafruit Bluefruit Low Energy nRF8001"));

  // Start BLE
  BTLEserial.begin();
 
  // Give name and ID to device
  rest.set_id("001");
  rest.set_name("my_arduino"); 
}

aci_evt_opcode_t laststatus = ACI_EVT_DISCONNECTED;

void loop() {  
  
  // 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();
  // If the status changed....
  if (status != laststatus) {
    // print it out!
    if (status == ACI_EVT_DEVICE_STARTED) {
        Serial.println(F("* Advertising started"));
    }
    if (status == ACI_EVT_CONNECTED) {
        Serial.println(F("* Connected!"));
    }
    if (status == ACI_EVT_DISCONNECTED) {
        Serial.println(F("* Disconnected or advertising timed out"));
    }
    // OK set the last status change to this one
    laststatus = status;
  }
  
  // Handle REST calls
  if (status == ACI_EVT_CONNECTED) {
    rest.handle(BTLEserial);
  }
}