Can't Connected the Blynk into HC05

Lately i use Blynk for my embedded system project. For the user interface, i’m using HC05 bluetooth module, but i get the problem in connecting the blynk app into HC05. Everytime i’m trying to connecting it, it would say “can’t connect, please check the auth…”
But i had paste the auth code from the mail that has been sent.

Here’s the code i’ve been used:

  Download latest Blynk library here:

  Blynk is a platform with iOS and Android apps to control
  Arduino, Raspberry Pi and the likes over the Internet.
  You can easily build graphic interfaces for all your
  projects by simply dragging and dropping widgets.

    Downloads, docs, tutorials:
    Sketch generator: 
    Blynk community:  
    Follow us:        

  Blynk library is licensed under MIT license
  This example code is in public domain.

  Note: This only works on Android!
        iOS does not support Bluetooth 2.0 Serial Port Profile
        You may need to pair the module with your smartphone
        via Bluetooth settings. Default pairing password is 1234

  Feel free to apply it to any other example. It's simple!

  NOTE: Bluetooth support is in beta!

  You’ll need:
   - Blynk App (download from AppStore or Google Play)
   - Arduino Uno board
   - Decide how to connect to Blynk
     (USB, Ethernet, Wi-Fi, Bluetooth, ...)

  There is a bunch of great example sketches included to show you how to get
  started. Think of them as LEGO bricks  and combine them as you wish.
  For example, take the Ethernet Shield sketch and combine it with the
  Servo example, or choose a USB sketch and add a code from SendData

/* Comment this out to disable prints and save space */
#define BLYNK_PRINT Serial

#include <SoftwareSerial.h>
SoftwareSerial SwSerial(10, 11); // RX, TX
#include <BlynkSimpleSerialBLE.h>
#include <SoftwareSerial.h>

// You should get Auth Token in the Blynk App.
// Go to the Project Settings (nut icon).
char auth[] = "3M2qyu4yJgyzuhxnbtt3PJLqi5u1EG43";

SoftwareSerial SerialBLE(10, 11); // RX, TX

void setup()
  // Debug console

  Blynk.begin(SerialBLE, auth);

  Serial.println("Waiting for connections...");

void loop()
  // You can inject your own code or combine it with other sketches.
  // Check other examples on how to communicate with Blynk. Remember
  // to avoid delay() function!

Please help me to solve this problem
thank you


@Zahira please edit your post, using the pencil icon at the bottom, and add triple backticks at the beginning and end of your code so that it displays correctly.
Triple backticks look like this:


Done sir, I already used 2 devices to connect Blynk to HC05 however, both of them didn’t work properly. Then I change into the other hc05 Bluetooth module, but it’s still didn’t works.
Please let me know if you can help in this matter. Looking forward to receiving your reply.
Thank you.

Your Auth token isn’t the problem, assuming that it matches the one for your Uno in the app.

How are you connecting your HC-05 to your Uno, and do you have any other devices connected to it?
What does your serial monitor show?

Do you have any other phones/tablets you can try this with?
Have you tried restarting your phone?


I connected the RX pin in HC05 to digital pin 10 in Arduino Uno. Then the TX pin in HC05 to digital pin 11 in Arduino Uno. I used a 5V pin in Arduino for the VCC pin of HC05.

No, I don’t put any other devices.

I already used 2 phones, and both of them give the same result.
Yes, sir, I restarted it, turn on the location mode and Bluetooth mode.

Pin 10 is the pin that the Uno is expecting to receive data on, it needs to be connected to the pin that the HC-05 is transmitting data on (Tx).
Pin 11 is the pin that the Uno is transmitting data on, the HC-05 will accept this data on its Rx pin.

So, it needs to be…
Uno pin 10 (Tx) to HC-05 Rx
Uno pin 11 (Rx) to HC-05 Tx


I did as you said, sir.
but it keeps showing like this

Have you tried a Bluetooth scanning app to show the details of all Bluetooth devices in the area?

Maybe try deleting and re-adding the BLE widget, uninstalling Blynk etc.


is it similar to pairing Bluetooth on phone to hc05?
if yes, yeah I already did it and put the password 1234.
Then they automatically paired.

If I tried another Arduino Bluetooth application, it can be connected as well.
I don’t know why Blynk can’t

is the arduino should integrared with wifi?
I use Arduino Uno smd R3

I don’t understand your question.


I mean, my arduino isn’t support for internet things.
And I choose HC05 bluetooth instead of wifi module.
I really don’t know what to do right now.
I already do all the things that have been told in youtube tutorial for connect Blynk to HC05.

Maybe try deleting and re-adding the BLE widget,
I don’t use bluetooth low energy sir, i use hc05 bluetooth module

Delete your Bluetooth widget from the Blynk app and re-add it.


It can be connected while i try in widget, but when i try to run the Blynk, it disconnected again.


I literally have the same problem, the serial monitor keeps showing
login timeout

over and over again

That’s a piece of information that you omitted from your own topic.


I also have the exact same problem.
The app keeps telling me that it can’t connect.
The serial monitor keeps saying [576089] Connecting...