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Thread: Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

  1. #1

    Question Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

    Hi Everyone,

    I am a Teaching Assistant in an undergraduate robotics lab and we are having some trouble. We have 12 Bioloid Premium kits that we are using, and we have written a ROS bridge and custom firmware to wirelessly control our kits from a ROS node running on a PC using the Zig2Serial adapter and Zigbee radios supplied in the kits. We are seeing an unacceptably high number of dropped packets (>30%) and very short range (max about 10 feet).

    So it looks like

    Student ROS Node <---internal PC comm---> ROS Bridge Node <---Zig2Serial/Zigbee--->CM-530 controller



    I've been tasked with finding an alternative solution and I ran across the Bluetooth set, which I have since noticed has been updated by Robotis to include the BT-210 radio as well. This would have the advantage that we would essentially be able to just swap the radios without any change in the code base.


    My questions are, would the communication over the Bluetooth radios be more robust than the communication over the supplied Zigbee radios? Are there other options I am not thinking of that would not require a huge cost or effort to implement?

    If we can't find a solution, we will go back to the direct embedded-C programming of the CM-530, but we were really hoping to introduce the students to ROS and have the easier debugging of programming for the PC.



    This is somewhat urgent, as we are now a couple of weeks in to our quarter and I need to act quickly before we get held up too much. Thanks in advance!

  2. #2
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    Re: Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

    What baud rate, what packet size, and how many wifi networks are in the area? With two official university 802.11g networks and 2~5 802.11g/n lab networks in the building, we get a solid 10 meters with both zigbee and the original bluetooth modules through cinder block walls. Have not done a test on the number of dropped packets, but it has never been significant enough to cause any noticeable issues with our usages.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  3. #3

    Re: Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

    I wouldn't expect Bluetooth to have better range than Zigbee. It's called a "personal area network" for a reason :-)
    If you need range, I would suggest going with something like an Xbee. That may mean some amount of hookup adaptation.

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    Re: Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

    Quote Originally Posted by jwatte View Post
    I wouldn't expect Bluetooth to have better range than Zigbee. It's called a "personal area network" for a reason :-)
    If you need range, I would suggest going with something like an Xbee. That may mean some amount of hookup adaptation.
    Bluetooth has three power classes: 1 (100 mW), 2 (2.5 mW), and 3 (1 mW) with ranges of ~100m, ~10m, and ~1m, respectively. There are Class 1 USB and embedded modules out there, but modules sold by Robotis are only Class 2.

    XBee would be nice with the 90+ meter ranges and awesome reliability (several years of use by most teams in the horrible interference at RoboGames MW), but they are quite a bit larger than the Robotis modules and may need a bit more current than the 3.3V power control transistor of the ZIG/BT-110 port of the CM-530 can supply (never tested that).
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  5. #5

    Re: Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

    Thanks for all the great feedback guys. It sounds like something else is going on that is causing it to not work well, since we are no where near 10 meters before the connection starts to drop (i.e. the red LED on the radios go from solid to blinking). We can't even get 10 feet.

    For reference, I'm using the standard 57400-8-1-N that is pretty much out of the box. There are a couple of wireless networks around, but the lab is actually in the basement and the outside signals don't reach that lab very well (my cellphone doesn't even get a signal, and until recently when they installed a new AP in the lab, we couldn't even get on the campus WiFi).

    So, would it matter than 12 kits are all going at the same time? Also, we are using the Zig2Serial adapters, which the ZIG-100 just presses in to. Would it be better to just solder the Zig-100 radios in to the adapter? I don't forsee using these radios in any other way. Basically, I would be happy with the performance you guys describe. Right now, the performance is no where near that.

    Thanks again guys. I knew you guys would have some good info.

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    Re: Bluetooth vs. Zigbee over PC Serial Port to control Bioloid CM-530

    It should not make any difference whether the modules are soldered or not. The only issue with the expanding pins is occasional dislodging of the module (mostly only happens in the RC-100 when dropped).

    The use of 12 kits may be contributing, but I would not expect it to be that significant since the zigbee spec is supposed to have 16 channels in 2.4GHz modules. Not sure how many channels are actually used in 1:1 mode of the Robotis modules, but in N:N (broadcast) mode: ZIG-100 has 4 channels, ZIG-110 is fixed on channel 1, and ZIG-110A is fixed on channel 4.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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