Friday, January 28, 2011

Router console via bluetooth

UPDATE 2/13/2013: I really like the look of the SEL 2924 bluetooth to serial adapter. It has integrated rechargeable AAA batteries and a micro-USB charing port. Power is the biggest problem with most devices of this type. If you spring for one of these, please post a comment about your experience with it.

My employer recently "upgraded" my laptop to a model that doesn't include a serial port.  I've got lots of USB/serial converters based on the Prolific 2303 chipset, and have used this chip for ages on various platforms, but the Windows 7 drivers for this chip have not worked well for me.

Rather than roll the dice with other chipsets and drivers, I decided to get what I really wanted:  a bluetooth serial port from BlueConsole.

Bluetooth is a huge advantage for me because it allows me to go find a chair while working in sometimes hostile environments (data centers, construction sites, manufacturing plants, mountaintop antenna towers), rather than do the balance-laptop-on-left-hand-while-typing-with-right-index-finger ballet.

Unfortunately BlueConsole is out of business, so I had to find something else.

The UConnect BT232B is the best solution I've found, and I'm happy enough with it to recommend it.  I got mine from US Converters.
It has some shortcomings:
  • It has thumbscrews instead of fixed female threads
  • The DE-9 connector is female, rather than male
  • It requires external power (either mini USB or through a small battery connector)

The thumbscrew problem was the easiest to resolve.  Remove thumbscrews, replace them with 4-40 hardware scavenged from an IT junkpile.  Three screws hold the plastic clamshell together, but two are covered by the sticker.  Sticker carnage:

Having resolved the thumbscrew issue, I installed a 9-pin gender changer and a Cisco console cable:

For power, I use an Energizer EnergiStick 250 charging dongle intended for cell phones.  It's a small 250mAh rechargeable battery with two mini-USB ports:  A male port for powering the adapter, and a female port for recharging.  This 250mAh battery should last almost 3 hours at the BT232B's rated maximum draw (90mA).  I've used it for at least twice that long without recharging, so the actual current consumption must be quite a bit lower.  Maybe I'm not typing fast enough :-)

It's like it was made for the BT232B:

Pass-thru charging is supported:  The Energizer battery can take a charge from a USB source while simultaneously powering the bluetooth radio.

The BT232B pairs easily with both Windows 7 and OSX.  Both platforms install it as a locally attached serial port: COMx in Windows and /dev/tty.mumble in OSX.  Its baud rate defaults to something other than 9600 baud.  I configured it once, and have not had to reconfigure it, so either it remembers its settings, or it's taking cues from my terminal emulator software.

The Windows 7 bluetooth drivers are kind of terrible.  If I'm linked up with the device and put my laptop to sleep, I need to delete the port and re-add it in the control panel in order to get it working again.  Under OSX it just works.

The radio performance has really surprised me.  I'd expected it to give me just a little bit more room to roam than the normal 6' Cisco cable, but it's way better than that.  I've used it over 50' in data centers, and 60' (through walls) in my house.  When it gets to the end of its radio range, it tends to get weird and slow, but doesn't drop characters.


  1. I've always thought that Bluetooth serial was the way to go. Just don't keep it hooked up for the bad people to try and crack! :)

  2. Heh,

    Several years ago I saw an *enterprise* BlueConsole deployment.

    Instead of running cables to a real terminal server, they hung blueconsoles off the front of switches around the data center, and used them by logging into a PC with a bluetooth interface via RDP.


  3. I'm assuming you had to build a custom cisco console cable to make this work. Mine worked fine with a rolled cable adapter, but not with just the gender bender.

  4. Nevermind... bumped the switch to DCE... /facepalm

  5. Great concept! I just put one together however I still can't access my router.

    I changed the baud to 9600

    Selected DCE

    My computer finds the bluetooth adapter with no problems. it installs to com port 11 and 12

    I've tried both with no success, what am I missing


  6. Try shorting pins 2 and 3 on the adapter with a paper clip. If everything's okay, whatever you type into a terminal emulator will echo back to the screen. If this test works, then look into stuff on the wired side of the bluetooth adapter.

  7. I finally got around to building one of these. I like it so far, until I try to get into a device. I've made sure the adapter is set for DCE, I've done the loopback test to ensure I am sending and receiving, that seems all ok. I've tested the cable to ensure it works, that's good....I'm lost, help please!!! I'm so close!!

  8. I just tested mine. Contrary to Jake's comment above, my adapter requires me to have the switch set for DTE.

    Maybe our various gender benders are rearranging the pins in different ways?

  9. Yeah, I attached the gender bender and tried the test like that. It still was sending traffic back to me. I'm using PuTTy to talk to it, so I'm wondering if it's sending on one COM and not talking back on the other, if that makes sense?

  10. I'm not following you. Which test?

    Paperclip *in* holes 2 and 3 on the bluetooth dongle should echo characters to the screen.

    Paperclip *touching* pins 2 and 3 on the gender bender should also echo.

    If you're crafty, you might be able to loop pins 3 and 6 (red and green) on the blue Cisco cable's 8P8C connector. Characters should echo in this case too, but it's tough to jam a paperclip in there.

    The only problem now is that we don't necessarily know which pin (2 or 3) is which (transmit or receive).

    Flipping the DCE/DTE switch should swap those around.

    The only other thing that occurs to me is... Are you testing against a Catalyst with "XL" in its name? These things have some funky hardware flow control requirements that may be screwing things up. I've never tested my bluetooth adapter against one of these, but they don't work correctly with other serial devices I've used.

  11. Yes, sorry, the paper clip test is what I'm referring to. I took the accessport software USConverters has on their site, did the paper clip test with both the DCE and DTE on, and received data back both times. After that, I hooked a console cable up to the adapter and stripped the red and green wire back to test the cable connection. It worked on both DCE and DTE....I'm using XP for this, could that be the issue? I see in device manager that there are two ports, like it said on the converters site, but it also only shows 1 com port being used by Win7. All I get is a black screen with a cursor. Also, I'm using a 3750G for the connection.

  12. Maybe it's a baud rate issue?

    I've never used the usconverters software, just a terminal emulator (putty).

    The red/green cable test is promising. You're sending characters out, and getting them back. That's all that should be required.

    Try fiddling with the baud rate on your terminal software, and also by talking to the adapter with a different serial port as described in the manual.

  13. I miss my blueconsole. I had to give it up when I changed jobs. Really wonder why they didn't make it, it was a great tool and the perfect form factor. If the creator is lurking out there, maybe he'd be willing to open source the schematics. :)

  14. I like your solution, specifically the battery, just wondering how you've been living with it a year later. I use a blueconsole, but honestly, life ain't all peachy, the software and firmware is old, and I'm scared to do somethings with it like change baud rate...if it's gone.

  15. how do I change the baud rate on this device? I have it connected to my cisco device and the com ports in my computer are set to 9600; but I can't connect to my cisco device.

  16. Anon: I continue to use it, but only once every 6 weeks or so. The battery has always been fresh, and Windows continues to be a slight bummer. Sometimes I need to remove/re-add it in the Windows device mangler. Other than that, it's been fine, and is still the best option in my opinion.

  17. Santucci4: You can change the baud rate by talking to it via serial when it's not paired with another device.

    See the BAUD= command on page 4 of the manual linked at the top of this post.

    I've done this exactly once, and haven't needed to touch it again. I don't know for sure that I needed to do it in the first place. Maybe the speed settings in PuTTy are doing the same job? Not sure as I've only ever used 9600,8,N,1

  18. All I get is this on a cisco 3640 will try a 3750 tomorrow (?øæøæþæøøæøþøàøæàþø?àæ?æà??ààæàææø??æàæææøææøæ?àæø?æþææ?æþæøàæ?þà?????øæ??àæ?øæ??àæ?æàæ?øæøøøøøøøøøøøøøøøøøøøøøøøøøøøø???)tons of when the switch boots up anyone have a similar problem.

  19. @xzatech,
    Did you set the baud rate on the adapter? This process involves plugging the adapter into a real serial port, and typing commands at it, as described in the manual.

  20. Chris, thank you for responding, after a closer read I see what your saying, your'e on the money . I need to connect the Bluetooth serial adapter to my keyspan<>usb to my laptop and then set the baud rate to 9600 getting rid of the 19200, I hope this does the trick it should. If it goes well, next I would to get to work on Fedora Linux with minicom. Thinking I'll just have to figure out how it recognize the tty line for Bluetooth usb is seen as tty="USB0" hmm maybe "blu0" LOL I have no idea :p..anyone use their device on fedora linux or any linux distro. let me know thanks again Chris

  21. @xzatech,
    Cool, I'm glad to know that you skipped that step. It makes sense that you're having trouble with it then.

    Actually, I'd been wondering if the step was really required, because "real" serial ports can be controlled with via software.

    I've only ever done this step once, and it was the first thing I ever did with the adapter (Hi, my name is Chris, and I'm obsessively addicted to reading product manuals...)

    The fact that I've never had to do it again left me wondering if it was really required. ...Of course I've never used it at a speed other than 9600 either.

    The only Linux distributions I've used with this device were Android devices, and the terminal emulator apps made it pretty obvious what device was appropriate.

  22. I'm up and running running running on Win7, next Linux and Android thanks again

  23. like the answer, exclusively this battery, only wondering how you've been living alongside it a year later on. I prefer a blueconsole, however seriously, living isn't just about all peachy, the application and firmware can be older, and Now i'm worried to try and do somethings about it like modify baud rate... in case it passes away... it really is long gone.

  24. I used the US Converters unit with the little battery for quite some time, and was happy with it. The main caveat is that it's impossible for me to change baud rate on the road (because that task requires a second serial port).

    I've been using the SEL2924 for 2+ years now, and I prefer it. It features:
    - rechargeable AAA batteries behind a tool-less battery door
    - charge via MicroUSB port (though it's not a great charger)
    - dip switches for speed
    - rollover (DCE/DTE) switch

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