I have a popular bluetooth module JY-MCU version 1.06 (picture below). Before i insert it to my arduino project I want to configure the name, bound speed and the pass code using usb-to-serial link. But I am facing a problem where the device does not respond to commands. Please let me explain.

I send the module to programming mode by applying +5V on 'key'

Then I send commands using CoolTerm program:

> OKyour set name

Ok. setting the name works as expected. But that is the only thing that worked for me. Other commands give no response:





Maybe you had this happen to you? I am I sending wrong commands or doing something wrong? Please help me to figure out how to control this module.

enter image description here

  • I've heard how sometimes you have to put it into "AT mode" by pulling up a pin to HIGH. It might be like the "KEY" pin (not entirely sure). Jan 7, 2015 at 18:49
  • Just a comment on configuring these boards: there is no provision for resetting them to default- or factory-settings. They remember only their most recent settings. Either write down how you last left it or always use it the same way - the serial settings especially! The only alternative, if you've forgotten the last settings, is to run a program that tests combinations of baud and serial-framing until it can establish communication with the device and set it to your new preferences. Glad you got yours sorted out!
    – JRobert
    Mar 9, 2015 at 21:22
  • I believe that the active IV on this is also known as the HC-06. You may also want to study relevant data sheet information on that device.
    – Kolban
    Jun 8, 2015 at 5:00
  • 1
    The board is actually called a Bluecore CSR Ext 4. Collioquially its known as an hc-05 bluetooth module. The jy name is tge breakout board it sits on
    – michael
    Jun 8, 2015 at 19:02

2 Answers 2


OK, I figured it out. It looks like CoolTerm was sending wrong line endings. Thus the only command that worked was name change as it interpreted the extra symbols as part of the name specification. Now I am using in built Arduino serial communication and it works like a charm!


The protocol is peculiar.

You are to send the command unterminated within one second.

For example the AT command comprises the two characters AT and nothing more, no line ending at all. And the command must be completed within one second.

AT[cr][lf] will just be ignored.

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