ATtiny85 - Bluetooth

In the last instructable I showed you how to program an ATiny85, in this instructable I will show you how to start serial communication with the ATiny85 over a Bluetooth network. For this instructable I will be using a HC05 Bluetooth module which can be purchased for cheap on eBay.

So lets get started....

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Step 1: Tools and Components

Here is what you need -

Step 2: Circuit

Setup the connections between the ATiny and the Bluetooth as follows -

  • Bluetooth Module Rx --> ATiny85 Pin 1
  • Bluetooth Module Tx --> ATiny85 Pin 2
  • Bluetooth Module Gnd --> ATiny85 Pin 4
  • Bluetooth Module VCC --> ATiny85 Pin 8

Step 3: Code

Here is a test sketch you can run, connect a led at 6 and upload the code. Sending 1 from a serial terminal will turn on the LED and sending 0 will turn it off.

#include //Software Serial Port
#define RxD 1 #define TxD 2

#define DEBUG_ENABLED 1 SoftwareSerial blueToothSerial(RxD,TxD);

int led = 4; void setup() { pinMode(RxD, INPUT); pinMode(TxD, OUTPUT); setupBlueToothConnection(); pinMode(led,OUTPUT); digitalWrite(led,HIGH); } void loop() { char recvChar; while(1){ //check if there's any data sent from the remote bluetooth shield if(blueToothSerial.available()){ recvChar =; if(recvChar == '1') digitalWrite(led,HIGH); else digitalWrite(led,LOW); } } } void setupBlueToothConnection() { blueToothSerial.begin(9600); //Set BluetoothBee BaudRate to default baud rate 38400 blueToothSerial.print("\r\n+STWMOD=0\r\n"); //set the bluetooth work in slave mode blueToothSerial.print("\r\n+STNA=HC-05\r\n"); //set the bluetooth name as "HC-05" blueToothSerial.print("\r\n+STOAUT=1\r\n"); // Permit Paired device to connect me blueToothSerial.print("\r\n+STAUTO=0\r\n"); // Auto-connection should be forbidden here delay(2000); // This delay is required. //blueToothSerial.print("\r\n+INQ=1\r\n"); //make the slave bluetooth inquirable blueToothSerial.print("bluetooth connected!\n"); delay(2000); // This delay is required. blueToothSerial.flush(); }

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    8 Discussions


    1 year ago

    #include <SoftwareSerial.h> //Software Serial Port

    #define TxD 0 //pin 5 de l'ATtiny à relier au pin RXD du module bluetooth (pin5)

    #define RxD 1 //pin 6 de l'ATtiny à relier au pin TXD du module bluetooth (pin4)

    SoftwareSerial blueToothSerial(RxD,TxD);

    int relais = 4; // pin 3 de l'ATtiny qui commande le relais

    void setup()


    pinMode(RxD, INPUT);

    pinMode(TxD, OUTPUT);


    //delay(2000); // délai nécessaire

    blueToothSerial.print("Bluetooth connecté !\n");

    delay(4000); //Vérifie que tous les relais sont bien inactifs après un reset


    digitalWrite(relais,LOW); // ouvre le relais


    void loop()


    char recvChar;

    while(1) {

    //vérifie s'il y a des données envoyées à partir du module bluetooth


    recvChar =;

    if(recvChar == '1')








    1 year ago

    i am trying with this library

    #include <SoftSerial.h>

    and... compiled!!


    3 years ago

    the first line of code should read as follows:

    #include <SoftwareSerial.h>

    ....I didn't get any compile error....


    3 years ago

    i am trying to make communication beteen attiny-85 and hc05 its not working bro plz help me


    3 years ago

    Any ideas on faster bitrate than 9600 ?