I'm trying to help a mate connect his drone via BT to set up rotor speeds.

I don't know whether this is a HC05 master/slave type or 06 which is only slave. There's no micro switch for set up mode but some seen to not provide that anyway. The vendor does not tell you anything more than "bluetooth", so you just have to guess what he's selling.

I found it is configured at 115200 baud and tested using Arduino IDE monitor.

It responds with OK when I send AT but nothing more works.

Any longer commands like AT+HELP just get ignored.  I cannot get any sense out of it.  I haven't used these devices before so I may be just unfamiliar, I was expecting to set the baud rate I need and verify it was fully working before attaching to the drone.

Can anyone help make sense of this?

Anyone here with good Bluetooth advice from a working setup please step in here.  :)

My advice is not the best because I generally use OpLinks.  Long ago where I tried to set up Bluetooth, I ran into problems where things had to be manually configured each time I wanted to use it.

I do remember it was a pain to find good HC05/06 documentation that actually matched my hardware.  Some documents seemed correct, but were different and just didn't work.

Have you seen the wiki pages?

I bet that the circuit for the button is there, but they left the button off to save money.  Maybe try to press the missing button with a rounded paper clip.  You might need to clean etc. to make contact.


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Hello groundcontrol,

Have a look here

The HC05 unit has 6 pins. I really never got success with these units. You need to press and hold the thing marked EN (or short them if no key is present on unit) on most units but not all, while booting up to make it enter in to config mode. I never made that work. Its more easy to use the HC-06 unit with 4 pins that can only act as a slave. Then you don’t need to worry about that.

Has anyone replaced the PCB antenna with a real one and got good range?  Say at least a few hundred meters?

I recall discussion where someone claimed their bluetooth was getting several hundred meters.  That might be enough to use for flight telemetry or control.


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Re: Trouble configuring bluetooth dongle. chinese knockoff HC05/06 style
« Reply #4 on: June 18, 2022, 01:08:00 am »
I use HC-05 for connecting to my RC transceiver (SIYI FM30) which has a separate uart channel accessible locally  only via bt. So it could act as a bridge between radio and the GCS. I spent almost a week trying to connect HC-05 to the FM30. I had no problem connecting to FM30 from the phone, pairing was always successful with pin 1234 (pin is required by FM30, is mentioned in the manual). The goal was let the
HC-05 (in master mode) automatically connects to FM30, but HC-05 always refused to bind and connect. In desperate mode I tried with pin 0000 and voila! It worked! Let me someone explain how pin 0000 worked when manual says it should be 1234 and 1234 works when connecting to from other bt devices to FM30?? Any way, I always say BT is the worst wireless technology ever invented.
Some useful details about HC-05 and it clones: it has two working modes: "normal" (act as transparent serial bridge)  and config, when it accepts AT commands. Config mode is active when HC-05 is booted up with pressed button (button could be released after entering config mode), serial speed in config mode is always 38400, normal mode could have different serial speeds (configured with at+baud= command). Some at commands are available only when button is still pressed. Some clones don't accept ending the command line  with /r/n, only /r.

Re: Trouble configuring bluetooth dongle. chinese knockoff HC05/06 style
« Reply #5 on: June 18, 2022, 08:18:25 pm »
My problem with Bluetooth has been that different brands of dongles that are supposedly compatible actually have different commands.  Finding the instructions that match the dongle is difficult some times.  Also, for my setup, I had to reconfigure it each time I wanted to use it.  I should try again with the helpful instructions here on the forum.
« Last Edit: June 18, 2022, 08:39:42 pm by TheOtherCliff »