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antoniocorregedor
antoniocorregedor
Associate II
April 29, 2012
Question

Best bluetooth module to use

  • April 29, 2012
  • 7 replies
  • 4766 views
Posted on April 29, 2012 at 22:17

Hi all,

I am currently using the STM3210C evaluation board to implement a prototype for a project I am currently busy with, and I am at the point where I need to add Bluetooth capability to my board.  In essence what I am trying to achieve is to stream the data from the STM3210C to another computer which is situated away from the STM3210C.

I was thinking of using a Bluetooth module as from what I can see on the net, there are Bluetooth modules which can be used to make ''wireless serial cables''.  So the idea is to use my eval board to interface to a Bluetooth module using the USART (RS232); and then pair the Bluetooth module to my laptop to get the information off the eval board.

I was hoping that this forum could point me towards an appropriate module which someone has possibly used in a project before, and that is easy to interface with the STM32 range.  Thanks in advance for any help which you guys can offer.   

Regards,

  Tony

#rs232 #stm3210c #stm3 #bluetooth
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7 replies

antoniocorregedor
antoniocorregedorAuthor
Associate II
May 1, 2012
Posted on May 01, 2012 at 11:28

From refining my search into Bluetooth modules, I have determined that the best module to use is the BlueSMiRF Gold (http://www.sparkfun.com/products/10268).  You interface to it using RS232 and it has all the required Bluetooth profiles so that it makes the process of interfacing to my PC easier.

ST does offer a module, the SPBT2632 (http://www.st.com/internet/imag_video/product/253470.jsp), which also contains the Bluetooth profiles and built in antenna; but with respect to fast prototyping, the BlueSMiRF offers a faster solution as it is better packaged for this.

I will order my self a BlueSMiRF and will post back my findings here once I have tested it out.

jvilaca
jvilaca
Associate II
May 2, 2012
Posted on May 02, 2012 at 02:01

I bought one from ebay <10€

There are a few available there based on the same ICs selling quite cheap.
donald2
donald2
Associate
May 2, 2012
Posted on May 03, 2012 at 00:36

I've used a number of the under $10 modules from FleaBay.

They are all based on the CSR chips, and they all have 3.3V CMOS serial connections that can connect to the STM32 pins without additional parts.

I suggest spending $1-$2 extra and buying a module with a baseboard and jumper cables.  You can hook it directly to a Discovery board for development.

The advertisements sometimes suggest that they have additional features, such as supporting audio or other bluetooth profiles.  The hardware might have this capability, but the firmware only supports the serial profile and serial output pins.

The only difference between modules is the details of the AT command set that configures the baud rate and a few other parameters.  You can usually figure it out with a Google search..  Often the sellers have copied their description from another vendor and have no idea if the instructions in their listing are correct for their module. 

bjfree
bjfree
Associate II
May 3, 2012
Posted on May 03, 2012 at 17:24

another thought is to use a wifi connection.

there are modules the use the SPI

if use

Microchip ZC2100M module

and

RN-131G & RN-131C

you can find both as break out boards

antoniocorregedor
antoniocorregedorAuthor
Associate II
May 3, 2012
Posted on May 03, 2012 at 20:28

Thanks all for your comments.  The reason why the Sparkfun module sounds appealing (http://www.sparkfun.com/products/10268), is because it comes with all the required data sheets (which contain all the commands that are needed to interface to it).  The only unappealing fact, is its price tag.

Donald (since you have used a few of these models) can you suggest a module which you have used in the past, that has given you good results.  If I am going to purchase a module (either than the Sparkfun one) I would like to purchase something which someone (like yourself) has used before with an ST board and has had good results.

freeman.bj, I will look into the wifi modules for perhaps future expansion.

donald2
donald2
Associate
May 3, 2012
Posted on May 03, 2012 at 21:01

They have all worked fine, and are essentially the same despite differences in layouts and which contacts the status LEDs are connected to.  Most of them ship with a default setting of 9600 8N1, and I make that the default for my development to avoid needing to figure out which 'AT' command works with the module I'm currently using.

I've only really needed to change the baud rate when setting them up as a serial console on Tegra boards.

They are far simpler to use than the alternatives because the bluetooth serial emulation is well specified.  There are no link options to screw up. Bluetooth doesn't require (or allow) that you set the target baud rate, parity, etc.  That sounds like a drawback, but once you have the module configured to your hardware you won't have to mess with it again.  Exactly what you want when you update an old embedded serial interface to support bluetooth.

antoniocorregedor
antoniocorregedorAuthor
Associate II
May 9, 2012
Posted on May 09, 2012 at 21:34

Donald,

Thanks for your comments, I have taken them into consideration when purchasing my module.

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