It all started when I was working on my Arduino project, which involves an Arduino Nano, an HC05 module and a bunch of sensors (DHT 11, soil moisture and LDR) with Blynk App. Everything worked as it should (compiled properly) but there was no transfer of data (HC05 was paired).

At that time before pairing, the HC05 was blinking rapidly and after pairing it was blinking twice rapidly every 5 seconds. Note I connected everything as the example said... (You know HC05s TX RX to HW Serial Pins vice-versa).

So later I tried again with everything stripped out (took out all sensors and just the barebones sketch) and added the button widget in the app to control the Nano's onboard LED). Again everything worked as it should but there was no connection between the HW and the Blynk APP (it was not switching on the LED).

Then I tried with an another Bluetooth app and it didn't work as it should. Then I got to know something's wrong with the board itself. So I tried to boot it into AT command mode with this Guide. But it wasn't accepting any commands (NO replies).

So what do I do?

NOTE: I didn't get any relevant question so sorry for that. And do you need anything else?

Edit: It worked. I dont really know how. I think there was maybe a problem with the voltage divider but not sure. Thanks for your time and answers.

3 Answers 3


Maybe you use the wrong baudrate with your hardware serial. Your tutorial states, that 38400 baud is the default, but I found other sources (HC-05), that say the default is 9600 baud (which is also true for my HC-06 modules). Try 9600 baud and if it still doesn't work try some other standard baudrates.

  • I tried 9600 also.... Commented Jan 30, 2018 at 11:37

This worked perfect for me HC-05

Try it out.


Try enetering AT mode and change the default baudrate for HC-05. Maybe use some higher baudrate, it improves communication. Also, check if you’re doing the serial reading properly.

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