Can anyone recommend a Bluetooth module? One with DTR broken out?

LeafLabs Garden » Support » Maple Hardware Support

Can anyone recommend a Bluetooth module? One with DTR broken out?

(10 posts) (3 voices)

Started 3 years ago by gbulmer
Latest reply from gbulmer

gbulmer
Moderator

I am looking to use bluetooth serial.
I intend to use it as both a communication path, and also for program upload from my Mac.
I'd eventually use it for comms to e.g. an Android phone, but that isn't important at this stage.

I want a serial bluetooth module that 'just works'; plug it in to Rx/Tx and power, and it works (probably defaults to 9600 baud).
I want one on a 'breakout board' so that I can just plug in a 0.1" pitch header, without having to make my own PCB.

I'd prefer a bluetooth serial (USART) module which breaks out the DTR signal, which I'd tie to RESET to make remote upload a bit easier.
I'd prefer a module which supports, at least 115200baud.

I'd prefer one from a consistent source in case I want more in the future.
I'd prefer one that uses an SMD module which is also available, in case I want to integrate it onto the PCB in the future.

Can anyone recommend a bluetooth module that satisfies most of that list of requirements?

Posted 3 years ago #
okie
Administrator

I'd recommend the Bluetooth Modem - BlueSMiRF Gold or Silver from Sparkfun:
http://www.sparkfun.com/products/10268
http://www.sparkfun.com/products/10269

I've used both of them. One uses the RN-41 module and the other uses the RN-42, which are both available from many distributors and Roving Networks.

Posted 3 years ago #
gbulmer
Moderator

okie - I looked at those parts, and AFAICT they do not have DTR out. Is that correct?

The data sheet says "33 GPIO10 I/O (remote DTR signal) Input to RN-41 with weak pulldown"

Posted 3 years ago #
okie
Administrator

Oops, you're correct, those boards don't break out DTR. This one does, and it has the same module, the RN-41:

http://www.sparkfun.com/products/10559

The Sparkfun breakout board is a little pricey. If you're needing more than a couple, I would buy the units raw straight from Roving Networks. I've contacted them before for quotes with good results.

By the way, the main difference between the RN-41 and RN-42 is that the RN-41 is higher power and communicates over larger distances. They are pin compatible.

Posted 3 years ago #
gbulmer
Moderator

okie - thanks for looking, but I believe the RN-41 doesn't expose DTR.

There is a pin which I think can trigger a remote DTR, the datasheet says:
33 - GPIO10 I/O (remote DTR signal) - Input to RN-41 with weak pulldown

but I want an output which is activated by a remote DTR so that it can be tied to nRESET, and enable the host PC to do a remote reset to make uploading easier.

Posted 3 years ago #
crenn
Moderator

This isn't quite what you're looking for in terms of pin out, but may be of some use:
http://www.seeedstudio.com/depot/bluetooth-bee-p-598.html?cPath=139_142

Posted 3 years ago #
okie
Administrator

gbulmer, if it doesn't have to be triggered by a DTR signal, I think you may be able to toggle other GPIOs by sending the modules certain commands.

Posted 3 years ago #
gbulmer
Moderator

okie "I think you may be able to toggle other GPIOs by sending the modules certain commands."

Interesting idea! I had a look at the RN-41 page (http://www.rovingnetworks.com/products/RN_41), and poked through the manuals, but I couldn't see anything about that except in the HID manual. I *think* I want to use the bluetooth device as a serial device, yes?

Posted 3 years ago #
okie
Administrator

gbulmer, I just noticed that this other RN-41 breakout board from Sparkfun looks like it has DTR broken out:
http://www.sparkfun.com/products/10559

I once did the thing I think you're trying to do (communicate with, reset, and program a microcontroller through a UART over Bluetooth). As a side note, I recall that, at the time, the Python Bluetooth packages didn't include support to toggle DTR and Bluez support was buggy. Do you know if this has changed? I ended up using the RN-41/RN-42 GPIOs.

In the first 60 seconds after powering up or reseting the RN-41/RN-42, you can enter "Command Mode" by connecting to it over a Bluetooth serial connection (or any time through hard-wired UART) and sending it the character string "$$$". Once in command mode, you can change the 60 second window to be infinite so that you can enter Command Mode any time over a Bluetooth serial connection. If your "regular data" might include "$$$", from Command Mode, you can make the special "$$$" string something else. You can do all sorts of things from Command Mode, including toggling GPIOs. For example, the following commands do these things:

"S@,8080" sets GPIO-7 to an output
"S&,8080" drives GPIO-7 high
"S&,8000" drives GPIO-7 low

To exit Command Mode, you send the character string "---".

This is all in the Advanced User Manual, and it's a recommended read (it's mind-opening to see all the things you can do):
http://www.rovingnetworks.com/resources/download/47/Advanced_User_Manual

Posted 3 years ago #
gbulmer
Moderator

okie - I had skimmed that manual initially, but had only noticed remote DTR, but reading it again, it looks like both are available. Cheers!

I have a C program to exercise the serial ports ioctl's.
It would be handy if Python worked. A friend has found an ioclt bug which might be in Node.js. So this level of signal can be very frustrating, and almost impossible to debug without a storage scope or USB sniffer. DTrace on the Mac is very useful for debugging too.

Posted 3 years ago #

RSS feed for this topic

Reply

You must log in to post.