# How to use Arduino Bluetooth module?

I am trying to get my arduino working over wireless (via bluetooth). I would like to send serial signal though it via bluetooth, but I am having some difficulty getting the bluetooth module I purchased actually showing up on any of my computer's bluetooth scan.

This is the skimpy datasheet for the module. It was made by someone in China (an individul, not a company - and that is why I do not really understand it)

Any help as to how I can get this connected to my PC would be great. ---Thank you---

Here is the bluetooth module that I have...

Here is the complete setup...

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I must say that I don't like this question. You didn't actually tell us what's wrong and where you're stuck, so please tell us. Does the module respond to AT commands? I can see that one LED is shining. Did the green LED turn on at any point? Does the mode button do anything? –  AndrejaKo Jul 12 '12 at 19:32
Also note that the module used BlueCore4-Ext chipset. CSR doesn't make the datasheet available, but some datasheet aggregation sites do, so search for bluecore4-ext datasheet and see what you get. I found some pretty interesting PDFs. –  AndrejaKo Jul 12 '12 at 19:40
I have a similar module. For me the gotcha was in the fact that you can only issue AT commands over the wired connection and before the module is connected through wireless. And of course you have to pair it before you can use it .. –  jippie Jul 12 '12 at 19:44
Also that big component near C8: Can you use multimeter and test what it is? It looks like a voltage regulator to me. Put the negative lead of the multimeter on the middle lower pin and the positive to the left pin, measure the voltage and then to the right pin, measure the voltage and post results. It should be turning the +5 V into +3.3 V. Also it that is the regulator, it's missing the capacitors C1 and C3, so it could be unstable. If it's not working properly, it could be making problems, since the actual radio will transmit up to 4.2 V. –  AndrejaKo Jul 12 '12 at 19:44
@jippie sorry I know so little. This is my first time using arduino (or anything like it). What is an AT command? How do I send one? –  Keegan McCarthy Jul 12 '12 at 19:47

I have worked with this module before and found that it only appears in a scan if it is in "data" mode. To put the module into data mode you have to drive the mode pin low. However the datasheet neglects to tell you that the module wont actually switch into data mode until the reset pin is pulled. Try driving the mode pin low, pressing the reset button, and then doing a scan again. Something called "HC-..." should appear.

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It looks like one of the many BTMxx or HC-xx series BT modules, I have a couple here of the HC05 variety with the exact same layout but different AT commands. It can get confusing...

Luckily that datasheet is actually pretty good, many vendors don't even link to one even though they do exist (just try asking a few of the eBay seller out there and see how many positive replies you get ;-) )
Unfortunately typical is the fact they didn't also give you the detailed BTM-05 AT command guide, which you would need to change the all important baud rate (since it's not given in your datasheet)

The AT commands (an old command type originally used with modems which stands for ATtention) are used to set various setting on the module (baud rate, name, role, etc) Usually you are only bothered about the baud rate and possibly role (master/slave)
They are detailed on page 4 of your manual. To use the AT commands you must set the command pin (pin 2) high to enter command mode, then send the command followed by \r\n. If the command pin is low you are in normal communication mode, where anything you send to the module will be transmitted.

Here is a snip from the AT command guide showing the baud rate command:

The lack of detail or examples can still make things confusing for the new user. TO use the above to set the baud rate to 9600N1 (9600, no parity, 1 stop bit) you would drive the command pin high and send:

AT+UART=9600,0,0

If successful you should receive OK back.

To query the current baud rate you would send:

AT+UART?

If successful you would get back +UART,9600,0,0 (assuming it was set to the above)

To find it, I think all you should need is power applied - I could see my module when powered on. It's possible the device is in master mode and not visible.
A good way to test the module is active would be to send AT over the UART and see if you get OK back. If successful you know it's working (at least to some extent). Then check the settings using the other AT commands.

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I've tried searching for it while the mode pin is both 1 and 0, neither of which allow it to show up in a standard bluetooth scan... –  Keegan McCarthy Jul 12 '12 at 21:42
See edits at end of answer, try sending AT and see if you get a response. Also one of LEDs should be on (blinking I think, until connected) –  Oli Glaser Jul 13 '12 at 4:45