Go Down

Topic: Problem responding Bluetooth HC-05 FC-114 after enabling AT mode (Read 3486 times) previous topic - next topic


Hello comrades,
I am using Arduino Uno and i have a problem with Bluetooth HC-05 FC-114. After enabling AT mode (the LED is blinking every two seconds) when i use the use the serial monitor to send the AT command it doesn't response.
I have tried a lot of sets of codes and solutions found in the web but none of them work.
Specifically i have tried the following solutions followed with their codes bellow:

1. BT TX to software serial 10-BT RX to software serial 11 or the opossite
2. 5V or 3.3 V to BT VCC, GND to BT GND
Then i connected the arduino to my pc, i loaded the code with no errors, i removed BT VCC, i was pressing the button on the BT module and i connected the VCC back again and i stopped pressing the button until the LED blinked for every two seconds. In the end, i opened the serial monitor with the choice for both NL & CR enabled in 9600 or 38400 bauds.

I have also tried using the hardware serials with the empty sketch.

As for the code i have tried some others like the one bellow:

Code: [Select]

#include <SoftwareSerial.h>

SoftwareSerial BTSerial(10, 11); // RX | TX

void setup()
  Serial.println("Enter AT commands:");
  BTSerial.begin(38400);  // HC-05 default speed in AT command more

void loop()

  // Keep reading from HC-05 and send to Arduino Serial Monitor
  if (BTSerial.available())
    //Serial.print("Reading from HC-05...");

  // Keep reading from Arduino Serial Monitor and send to HC-05
  if (Serial.available())
    //Serial.println("Reading from Serial Monitor...");

I have also tried the method with uart micro controller without an outcome, and three different terminals (putty, hyper terminal, tera terminal)

I have attached some photos of my Bluetooth module.


1. BT TX to software serial 10-BT RX to software serial 11 or the opossite
2. 5V or 3.3 V to BT VCC, GND to BT GND
attach some photos of my Bluetooth module.
You do realize that blue tooth module has 3.3v limitations on the data lines?  (Look at your Photo)
Example of Master/Slave HC-05 FC-114 usage

The Uno uses 5V on it's data lines.

You are going to have to use some type of level shifter or change to an Arduino that uses 3.3V


Check out my Kickstarter Project Memory Panes an expansion RAM Shield for Mega2560's.  It adds 1MB of RAM for those projects where 8KB is not enough.

Currently built mega http server, Now converting it to ESP32.


That code requires both hardware and software serial at 38400. Is your serial monitor set for that speed? If not, I would be inclined to change the Serial.begin to 9600.,

You are probably wasting your time using 3.3v power. Stick to 5v.

Using a divider 1k/2k divider on Arduino Tx is a good idea but, if you have not done that, don't panic, you have probably not done any damage.

Using a 3.3v Arduino is a bad idea and may cause more problems than it fixes.

I found this guy pretty useful for the ZS-040-type board.



am having exactly the same problem as yours so if u mind plz how did u solve it  ?

Go Up