I have looked on various posts and downloaded about 5 sketches, checked Baud rates and my HC05 still won't reply OK when AT is sent in serial monitor.I am using Win 7. I can get it to blink slowly by plugging in the 5v and holding the button on the HC05 so I assume it is in AT mode. I can replicate 'Blink' and 'Hello World' but really need some help as I have about 3 stages I need to complete. 1. V3 Elechouse sketch to recognise speech. 2.Then the Arduino Uno via HC05 to send the information Left, Right and Forward to another Bluetooth Relay module to operate 3 relays. I KNOW it was ambitious of me. I just thought ( stupidly ) Cutting and pasting sketches would be easier. A contact or email of someone who could help would be appreciated. Regards
Please do not cross-post. Other thread removed.
If you look at my YouTube video #36 it describes how to get an HC-06 (very similar to an HC-05) talking. URL in the footer of this post.
Thanks Ralph, I am really impressed with the amount of videos you have done. I got to the point on vid #36 where I need to connect my USB Uart to the HC05 ( looks like I have a CP2104 ) and have pins GND, RXD, TXD, 5v, 3.3v and DTR. If I connect the 5v to VCC on the HC05 surely I need a divider for RX on the Uart to the HC05 as I thought RX should be 3.3v ?
When connecting to an Arduino, certainly the RX/TX pins must be via a divider (1K/2K will do just fine) although the unit can run off 5v (Vcc), if that's what you're asking.
I seem to remember emphasising that you can't connect a 5v Arduino pin to the RX/Tx pins of the HC-06 (or HC-05) but it's only two resistors (or a level shifter but that's overkill for this application).
When connecting to a USB-to-Serial connector then the version I used had a switchable 3.3 / 5v output so obviously I used the 3.3v and all was well. If you DON'T have that option then use the same resistor divider as above.
Which I think, after all that rambling, was what you were asking / confirming. Is that right?
And as you were kind with your feedback on my videos please consider (if not already) becoming a subscriber as there are many more projects in the pipeline and that way you won't miss any! (And I get confirmation that my efforts are not being wasted too). Cool. It's good that information can be shared like this.
Thanks Ralph. Nice to find someone who speaks at my level. Just after I posted I checked the voltage at RX and it was 3.3v so decided to try my old HC06 as per your video. OK was the reply. First time ever. Tried the HC05 module and nothing, but I really need a master and for it to run through the arduino Have to buy another HC05. BTW have you had any experience with voice modules? This thing is driving me Snuts !! Thanks again. P.S. Will subscribe
RayNiewolik:
OK was the reply. First time ever. Tried the HC05 module and nothing, but I really need a master and for it to run through the arduino Have to buy another HC05.
The difference between an HC-05 and an HC-06 is the firmware (I think) and why they would even sell the HC-06 beats me when the HC05 can do everything the HC-06 can do (and more).
I even think that you can set the HC-06 to be a master with some jiggery-pokery but that required more investigating time than I had available. But I will do another video on the HC-05 in the future as I would like to experiment with it.
BTW have you had any experience with voice modules? This thing is driving me Snuts !!
Voice modules? The fact that I question what you mean probably indicates the answer is no but please elaborate; it might be something I should be interested in!
Thanks again. P.S. Will subscribe
Brilliant. I can ask for no more 
Ralph in your link there is sub_confirmation=1 please delete that part
In my experience...
AT mode for the hc05 is substantially different than that for the hc06.
First, I was using a USB to UART converter similar to yours and simply connecting:
USB converter RX to hc05 TX
USB converter TX to hc05 RX
USB converter +5v to hc05 VCC
USB converter GND to hc05 GND
I didn't do anything with level shifting, resistor dividers, etc... and mine have worked for a long time. But I don't claim that this is safe, do so at your own risk. I've read plenty about the need for the divider resistors...just question whether it is reliable info or typical internet misinformation.
I have 3 or 4 hc05 modules, and to use the AT commands every one of them requires this:
-
power up the hc-05 while holding in the onboard pushbutton, then release the button. the module should go into programming mode and the led should blink about once every two seconds.
-
open arduino serial monitor. Line ending should be set to “Both NL & CR”
3.Baud speed should be set to “38400 baud” for the AT programming mode.
You mentioned baud in the OP, but its unclear whether or not you had it set at 38400?
There are now several different modules that share the same breakout board. For example, the boards that have the small push button switch tend to be marked zs-040. However, I now have 3 (possibly 4) different modules that use this and all have different firmware.
Another one that is starting to become common is the fc-114. I now have 2 different modules that use this board.
If you are still having difficulties with the HC-05 post a clear image of the boards you have. Or post a link to where you bought them from.
If you have the regular zs-040 board then not all AT commands work unless pin 34 is kept HIGH. An easy way to achieve this is to close the button switch (an keep it closed) just before you send the command.
MartynC:
There are now several different modules that share the same breakout board. F
And I think, several different breakout boards that share the same module.
Billcat, thank you for replying. I checked out the Uart voltage and it is 3.3v. I tested it with the HC06 and when AT is entered in the serial monitor I get OK back. When I try the HC05 nothing happens even with the same settings. I have ordered another HC05. I will have to wait until it arrives. I will test it with baud rate 38400. Thanks again
MartynC thanks for the reply. It looks like I have the zs-040 HC05 even though it hasn't anything written. I have tried it on a couple of Arduino Uno's but still have no reply when I send AT, it never says OK. I have checked the link you gave. I have looked at it before but still draw a blank. I have ordered another HC05 but will have to wait until it comes. Is the pin 34 the same as the en pin? Regards
RayNiewolik:
Billcat, thank you for replying.
Sure, hope it helps...
RayNiewolik:
I checked out the Uart voltage and it is 3.3v.
again, I think the hc05 is 5v tolerant, but can't guarantee. Mine have worked for a year or more at 5v with no resistors, level shifters, or the like.
RayNiewolik:
I tested it with the HC06 and when AT is entered in the serial monitor I get OK back. When I try the HC05 nothing happens even with the same settings. I have ordered another HC05. I will have to wait until it arrives. I will test it with baud rate 38400. Thanks again
My hc06s work exactly as yours regarding the ok response. But my hc05s are a different beast. They must be sent AT commands at 38400 baud, after entering programming mode. FWIW, all three of my hc05`s have the zs-040 marking.
I'm unclear from your wording, but it seems maybe you didn't try at 38400 baud, but are waiting to try that on a new hc05?
Hi Billcat,
I left all of the Arduino bits in my workshop, so won't be able to try until early Monday. I will try your suggestion of the HC05 and the higher baud rate. I could do with the sketch and wiring coupled up with the Arduino Uno if you have one and also with a HC06 just to test the OK reply through Arduino. I have never got a HC06 or HC05 to reply OK through the Arduino so I am starting to doubt myself. Is it the sketch, BT or Arduino ? I take it from the time of your reply, you are in the Good ol USA ? Uk here.
RayNiewolik:
Is it the sketch, BT or Arduino ? I take it from the time of your reply, you are in the Good ol USA ? Uk here.
No sketch or arduino needed for simple sending of AT commands, just the hc05 module and the usb to uart converter, connected as I mentioned previously. You will need the serial monitor or another terminal software like putty, etc.
Yes, I'm in USA
I really think your troubles are from not setting baud at 38400 for the hc05:-)
Hi Billcat, just tried HC05 with Baud rate at 38400 and no response to AT. Plug the HC06 back in with baud rate set to 9600 and get OK every time. Do you still think it's settings ? Regards
RayNiewolik:
Do you still think it's settings ?
Maybe...
If (you held in the button while you powered the hc05, and it entered programming mode. This is
demonstrated by the led flashing slowly about once every two seconds,)
and If (you had Arduino serial monitor set for 'both NL and CR' and 38400 Baud)
and If (you then typed 'AT', pressed enter, and still did not get the 'OK' response)
and If (your connections are the same as I have shown in the attached pic)
Then (I don't think its settings, but I can suggest no further advice, perhaps the module is different than mine, or is damaged...)
I tested this exact procedure just now, all of my hc05 modules require this exact method for sending AT
commands...
good luck!
Hi Billcat. Tried all of your suggestions and still no OK in AT mode. I should get my new HC05 today so will keep you posted, thank you so much for your help and advice. Had the V3 Voice Recognition up and running yesterday, so I am getting there.
Hi Billcat,
still haven't received the new HC05 so set the broken one up as per your instructions, still nothing, swapped the TX and RX round as I had nothing to loose, obviously still nothing, swapped them back to your layout and it started working again. How weird. Thanks again.