# HC-05 AT MODE not working **URL:** \ **Category:** Networking, Protocols, and Devices\ **Created:** [October 13, 2024, 6:57am UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757 "2024-10-13T06:57:37Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 13, 2024, 6:57am UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/1 "2024-10-13T06:57:37Z")
I have a hc-05 bluetooth module and I want to connect it to my arduino to enter the at mode, so I can change it to master and find out the adress. I have confirmed than the module is working because it appears in the bluetoth settings on my phone. I wired the module to the arduino with a voltage divider and set the baud rate 38400 and to both nl&cr in the serial monitor. I uploaded the blank sketch i tried using software serial but none of that made anything appear in the serial monitor. When powered on the module enters at mode because i hold the button and i see led blinking slowly. Can somemone please help me? P.S I am using a Arduino uno r4 Minima if it is relevant. ---
**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\ **Post date:** [October 13, 2024, 3:12pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/2 "2024-10-13T15:12:14Z")
Hello @pamet32 - Please, show your wiring diagram and sketch. ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [October 13, 2024, 4:11pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/3 "2024-10-13T16:11:19Z")
> [@pamet32](#): > > it appears in the bluetoth settings That doesn't mean it is correctly wired to Arduino, it just means that the power is on. ---
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 14, 2024, 2:12pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/4 "2024-10-14T14:12:56Z")
My wiring diagram is like this: ![Posnetek zaslona 2024-10-14 161224](https://europe1.discourse-cdn.com/arduino/original/4X/3/d/f/3df2c55f2f5d48a7a3f13e96d397412730f5db1c.png) and i used a blank sketch. ---
**Author:** ![gilshultz](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gilshultz](https://forum.arduino.cc/u/gilshultz)\ **Post date:** [October 14, 2024, 4:10pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/5 "2024-10-14T16:10:48Z")
Please post an annotated schematic. Your picture doesn’t clearly show the connections. ---
**Author:** ![anon85221860](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@anon85221860](https://forum.arduino.cc/u/anon85221860)\ **Post date:** [October 14, 2024, 10:18pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/7 "2024-10-14T22:18:24Z")
To be in 'AT' mode, I believe 'EN' has to be connected to 3V. (Assuming yours is the version with the pushbutton.) ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [October 14, 2024, 11:37pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/8 "2024-10-14T23:37:07Z")
> [@pamet32](#): > > and find out the adress. You should be able to get the address on the phone - no AT mode required. ---
**Author:** ![cattledog](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/cattledog/32/217816_2.png) [@cattledog](https://forum.arduino.cc/u/cattledog)\ **Post date:** [October 14, 2024, 11:56pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/9 "2024-10-14T23:56:17Z")
> [@Nick\_Pyner](#): > > The connections are Rx to Tx and Tx to Rx. @pamet32 said > and i used a blank sketch. With the blank sketch method is used and the Arduino only serves as a serial pass through to the module then it does not want the cross connection. [https://howtomechatronics.com/tutorials/arduino/how-to-configure-pair-two-hc-05-bluetooth-module-master-slave-commands/#h-configuring-the-hc-05-bluetooth-module-at-commands](https://howtomechatronics.com/tutorials/arduino/how-to-configure-pair-two-hc-05-bluetooth-module-master-slave-commands/#h-configuring-the-hc-05-bluetooth-module-at-commands) I have indeed used this blank sketch method and it can be successfully used to work with AT mode. ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [October 15, 2024, 1:33am UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/10 "2024-10-15T01:33:24Z")
> [@cattledog](#): > > blank sketch method Oops! I will delete my post to avoid confusion. I have never used that method. ---
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 15, 2024, 12:37pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/11 "2024-10-15T12:37:07Z")
> [@Nick\_Pyner](#): > > You should be able to get the address on the phone - no AT mode required. Thanks, but i want to change the role of it too. ---
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 15, 2024, 12:38pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/12 "2024-10-15T12:38:08Z")
> [@anon85221860](#): > > To be in 'AT' mode, I believe 'EN' has to be connected to 3V. > (Assuming yours is the version with the pushbutton.) Yes i know i just forgot to include it in the schematic. ---
**Author:** ![anon85221860](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@anon85221860](https://forum.arduino.cc/u/anon85221860)\ **Post date:** [October 15, 2024, 1:32pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/13 "2024-10-15T13:32:20Z")
Perhaps you could upload a pic of the device in question? (Maybe it's not AT-able.) ---
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 15, 2024, 3:33pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/14 "2024-10-15T15:33:57Z")
Here are two pictures of it: ![20241015_173149](https://europe1.discourse-cdn.com/arduino/original/4X/5/4/2/542c05448febc0c1b8188de0f9be198f6cce6356.jpeg) ![20241015_173152](https://europe1.discourse-cdn.com/arduino/original/4X/9/1/0/91054dd950da16a9174c63b3a9b43d2ac0cb5b01.jpeg) ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [October 15, 2024, 9:58pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/15 "2024-10-15T21:58:06Z")
This is just a red herring. It is an HC-05, and the fact that you put it in AT mode by pushing the button already attests to that. I guess I have to ask: have you had it working as a slave? If not, a simple hello to the phone with suffice - after you have changed the wiring. ---
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 16, 2024, 2:54pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/16 "2024-10-16T14:54:27Z")
I am not so sure what you mean, could you explain it to my a little better please? ---
**Author:** ![cattledog](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/cattledog/32/217816_2.png) [@cattledog](https://forum.arduino.cc/u/cattledog)\ **Post date:** [October 16, 2024, 3:48pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/17 "2024-10-16T15:48:59Z")
> [@pamet32](#): > > I am not so sure what you mean I think that we just want to confirm that the module is working properly in communication mode. You are using the blank sketch method, but there is an alternative way to use an Arduino and a serial-in serial-out sketch. It is described in detail in Martyn Currey's Website. [https://www.martyncurrey.com/hc-05-zg-b23090w-bluetooth-2-0-edr-modules/](https://www.martyncurrey.com/hc-05-zg-b23090w-bluetooth-2-0-edr-modules/) Scroll down until you find the section titled > HC-05 (ZG-B23090W): Communication and AT commands I would try the alternative method using the sketch. One thing that may be an issue is that with the blank sketch procedure as linked by Mechatronics the voltage divider from the communication mode maybe an issue with the signal levels in the pass through mode. ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [October 16, 2024, 4:39pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/18 "2024-10-16T16:39:14Z")
> [@cattledog](#): > > the voltage divider from the communication mode maybe an issue with the signal levels in the pass through mode. Wow! I hope that's true. Pass-through IS the alternative, I always thought it was a dumb idea, and now I want to be sure of it... ---
**Author:** ![pamet32](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/pamet32/32/1111672_2.png) [@pamet32](https://forum.arduino.cc/u/pamet32)\ **Post date:** [October 16, 2024, 5:55pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/19 "2024-10-16T17:55:54Z")
Thank you so much @cattledog you have solved my problem i am so happy. Thank you very much. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [April 14, 2025, 5:56pm UTC](https://forum.arduino.cc/t/hc-05-at-mode-not-working/1310757/20 "2025-04-14T17:56:04Z")
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