Published March 7, 2020 © GPL3+

Simple FSM example with HC-06

A finite state machine example using bluetooth module

IntermediateFull instructions provided3,097

Things used in this project

Hardware components

Arduino UNO

HC-06 Bluetooth Module

LED (generic)

Resistor 1k ohm

Breadboard (generic)

Jumper wires (generic)

Software apps and online services

MIT App Inventor 2

Story

In this tutorial we will build a simple FSM (Finite State Machine) example with Arduino Uno and HC-06 Bluetooth module

Theory

A finite state machine is a computational model that can be in exactly one of a finite number of states at any given time. It stays in one state until it is triggered by a specific input. The change from one state to another is called transition.

In this example each state is represented by a LED. We have three states RED, GREEN, BLUE. The transition is made by three inputs R G and B.

Diagram of FSM example

State transition table

Bluetooth module

HC-06 is a bluetooth module designed to establish communication between two devices and acts only as slave device. The pins we use are VCC, GND, TX and RX

Bluetooth connection

VCC is connected to 3.3 Volts

GND to ground

TX to RX pin of Arduino

RX to TX pin of Arduino

RX pin must be connected through a voltage divider because a direct connection to 5V may damage it.

Android application

In order to interface the android device with the Arduino I designed a simple application using the MIT app inventor.

Block diagram of application

After the first initialization the android device connects to the HC-06's MAC address. Then we hit each button to trigger the FSM and force the transitions. Bear in mind that the android protocol uses ASCII code in decimal format and thus we have to set the bluetooth accordingly.

ASCII table

From the above table we find that the ASCII codes for R G and B characters are 82, 71 and 66 respectively.

Circuit operation

Whole circuit

Each LED represent a state. The transition among the states becomes through the commands, sent by the HC-06. Initially the machine starts at RED.

Code

FSM with HC-06

#include <SoftwareSerial.h>

SoftwareSerial BTserial(13, 12); // RX | TX

#define BLUE 2
#define GREEN 4
#define RED 7

int command;

void setup() {
  BTserial.begin(9600);
  pinMode(GREEN,OUTPUT);
  pinMode(RED,OUTPUT);
  pinMode(BLUE,OUTPUT);
  digitalWrite(RED,HIGH);  
}

void loop() {

    while(BTserial.available()){
      command=BTserial.read();
      switch(command){
        case 82:  //ASCII code for R
          digitalWrite(RED,HIGH);
          digitalWrite(GREEN,LOW);
          digitalWrite(BLUE,LOW);
          break;
          
        case 71:  //ASCII code for G
          digitalWrite(RED,LOW);
          digitalWrite(GREEN,HIGH);
          digitalWrite(BLUE,LOW);
          break;

        case 66:  //ASCII code for B
            digitalWrite(RED,LOW);
            digitalWrite(GREEN,LOW);
            digitalWrite(BLUE,HIGH);
            break;

        default:
           //Nothing happens    
        }         
        delay(100); 
    }
}

Credits

xristos_xatz

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Simple FSM example with HC-06

Things used in this project

Hardware components

Software apps and online services

Story

Theory

Bluetooth module

Android application

Circuit operation

Schematics

Whole circuit

Code

FSM with HC-06

Credits

xristos_xatz

Comments

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Simple FSM example with HC-06

Simple FSM example with HC-06

Things used in this project

Hardware components

Software apps and online services

Story

Theory

Bluetooth module

Android application

Circuit operation

Schematics

Whole circuit

Code

FSM with HC-06

Credits

xristos_xatz

Comments

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