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Thread: Arduino & AX-12

  1. #1
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    Question Arduino & AX-12

    Dear Community:

    I have an Arduino and some Robotis AX-12s. Can they be used together?

    Yours,
    Steam Automaton

  2. #2
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    Re: Arduino & AX-12

    The problem with a standard Arduino is that it only has 1 serial port. Thus, you can communicate with the AX-12s, or with a controller/computer -- but not at the same time.

    The ArbotiX is an Arduino-compatible controller based on a bigger AVR chip, which has 2 serial ports. We have a full set of libraries for interfacing with the AX-12s (http://arbotix.googlecode.com). You probably could make the libraries work with an Arduino, but with some modifications (and, you'd not be able to communicate with your arduino to tell the robot what to do, or get debugging information back out of it via the serial port).

    -Fergs

    Standard Disclaimer: I'm the designer and developer of the ArbotiX hardware and software.

  3. #3

    Re: Arduino & AX-12

    I'm pretty sure the Arduino can do software serial on any pin though, up to 9600 baud or something. But the ArbotiX seems to be a pretty much ready made controller for all the Robotis servos, in that it had the connectors right on the board and all the libraries available, so you could save yourself a lot of trouble while still being able to use all the Arduino code you like.

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    Re: Arduino & AX-12

    The issue with software serial is that it's really only good for sending -- if you try to receive on software serial, it really eats up the processing power (and tends to have poor performance, you'll miss a lot of bytes of data). Thus, you need your hardware serial port gets eaten up by the PC-side connection.

    I know the last time I looked at it, the SoftwareSerial library for the Arduino allowed sending at up to 38400bps, but that was pretty much maxing out the processor from what I gather. Unfortunately, if you're controlling more than a few servos, and want smooth control, you'll probably saturate the bus bandwidth at 38.4kbps -- and thus, the Arduino is entirely maxed out, with no processing power to do anything else. So, I guess it's probably doable, but at that point, you've turned an Arduino into a USBDynamixel (and a slow one, at that)

    -Fergs

  5. #5
    zoomkat Guest

    Re: Arduino & AX-12

    I don't have any AX-12 servos, but you should be able to connect the servo serial connection to the tx/rx points on the arduino board. I have the rx on my ssc-32 servo controller connected to the tx point on the arduino and it works quite well.

  6. #6

    Re: Arduino & AX-12

    Ah I see. I haven't played with an Arduino so I'm not completely clued up on it. Just out of interest, do you think an Arduino would make a decent sensor server on the AX-12 bus? I.e. read a few sensors hooked up to it, and respond when queried over the AX-12 bus like an AX-S1. It seems to me that it would be pretty useful to be able to use whatever sensors you wanted, especially with the USB2Dynamixel or Jon's Wifi board.

  7. #7

    Re: Arduino & AX-12

    Quote Originally Posted by Chench View Post
    Ah I see. I haven't played with an Arduino so I'm not completely clued up on it. Just out of interest, do you think an Arduino would make a decent sensor server on the AX-12 bus? I.e. read a few sensors hooked up to it, and respond when queried over the AX-12 bus like an AX-S1. It seems to me that it would be pretty useful to be able to use whatever sensors you wanted, especially with the USB2Dynamixel or Jon's Wifi board.
    Jon makes an I/O board that does exactly this. It can also drive motors.

  8. #8

    Re: Arduino & AX-12

    Yes, I know, but you are limited to reading analog and digital pins. You couldn't, for example, read pulse widths, read/write serial communications or i2c, control r/c servos etc. I'm sure it'd be possible to add this sort of thing to Jon's board, but I'm not sure how easy that'd be compared with the Arduino which has lots of code available.

  9. #9
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    Re: Arduino & AX-12

    Quote Originally Posted by Chench View Post
    Ah I see. I haven't played with an Arduino so I'm not completely clued up on it. Just out of interest, do you think an Arduino would make a decent sensor server on the AX-12 bus? I.e. read a few sensors hooked up to it, and respond when queried over the AX-12 bus like an AX-S1. It seems to me that it would be pretty useful to be able to use whatever sensors you wanted, especially with the USB2Dynamixel or Jon's Wifi board.
    Yep, you can do that. I've got a modified version of the ArbotiX libraries that implement an AX-bus slave for mega168 chips. I've been using a modified MINI robocontroller (which is basically an Arduino), to control 8 mini servos, which are then connected to the AX-bus. I haven't gotten around to releasing the AX-slave code yet though.

    -Fergs

  10. #10

    Re: Arduino & AX-12

    Sounds good!

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