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Thread: Parallax Propeller--> Ax-12 circuit help

  1. #1

    Parallax Propeller--> Ax-12 circuit help

    Hello! Someone suggested I post this on the forums in case anyone else had the same questions.

    I would like to control some AX-12 servos using a Parallax Propeller based microcontroller.

    There is code a "Object" here (thanks to Mike Gebhard and Henk K for that), but now I am stuck on how to breadboard the circuit to make it work.

    I still suck at reading circuit diagrams. I only made it through the BasicStamp 2 :"What is a microcontroller?" book because it had drawings of what the circuits should look like on a breadboard.

    So I was wondering if anyone had a digi-pic of an ax-12 controlling circuit on a breadboard that they could share. Or maybe just a drawing. Or just helpful explanation of the logic of the circuit itself with parts labelled for dummies.

    In case you are curious about what I am using:
    Propeller System Module

    It has pins 16-23 free for general I/O and provides power source and ground. It's a pretty groovy piece of hardware for the price - LCD, Propeller Micro, 3-axis accelerometer, sd card bay, headphone jack etc. for 99$
    Last edited by altwolf; 11-13-2009 at 12:10 PM.

  2. #2
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    Re: Parallax Propeller--> Ax-12 circuit help

    Where's the schematic you're trying to read?
    I Void Warranties´┐Ż

  3. #3
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    Re: Parallax Propeller--> Ax-12 circuit help

    TX = P30 Pin39 "Prop manual pg. 17 for pin assignments"
    RX = P31 Pin40
    VSS is commone ground

    So from the ax12 gnd goes to VSS. AX12-Data is Data on the AX12 connector goes to the resistor circuit.
    And the 10Volts to the AX12 goes to the middle pin on the connector. Do not hook 10V to the prop just a caution this much voltage will blow out pins.

    Since the prop is a 3.3v chip you need to protect it from the 5V pull up. The resistors just limit current and make it tolarable for the pins.

    Just a quick response hope it helps.
    Last edited by Quantum; 11-13-2009 at 03:15 PM.

  4. #4

    Re: Parallax Propeller--> Ax-12 circuit help

    Here ya go.



    Power connected to second AX-12 cable


    Power connected to the same AX-12 cable


    The inline 1k resistors limit current to the Prop pins. Pin 2 is the port conected to the AX-12 bus. Pins 0 and 1 are Rx/Tx for serial TTL devices. On the demo board Pins 30 and 31 connect to the virtual PC serial port via FTDI.

    The 1k pull up holds the 1/2 duplex bus high during idle. Ya need that.
    The 10 to 100k resistor from signal to ground helps when you have many AX-12 on the line and it makes timeout detection a little more sensitive.

    Do NOT wire AX-12 power into the Prop only the AX-12!
    DO connect power ground and signal ground (prop Vss) together.

    Wow I wrote that drive a few years ago. Glad folks are using it. You can find the original over here
    http://www.agaverobotics.com/product...?node=products

    Still under construction. Anyway the DynaBus download has a manual with pretty pictures.
    Last edited by MikeG; 11-14-2009 at 11:22 AM.

  5. #5

    Re: Parallax Propeller--> Ax-12 circuit help

    Mike G and everyone else who has posted - You are Awesome! Thanks for all the info; it helped a lot.

  6. #6

    Re: Parallax Propeller--> Ax-12 circuit help

    No problem.

    FYI, I handled timeouts a little differently then the file on the object exchange.

    Kinda' funny how things workout though. I just dusted off the DynaBus for use in another Dynamixel project. I plan to change the way packets are buffered. I also want to move more of the bus logic out of spin and into assembly. We'll see, lot to do and no time.

  7. #7

    Re: Parallax Propeller--> Ax-12 circuit help

    Do you plan to post your improvements to the Dynabus object online? I, for one, would like to check them out.

  8. #8

    Re: Parallax Propeller--> Ax-12 circuit help

    Yes, updates will be published at http://www.agaverobotics.com/product...?node=products

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