Author Topic: Robotis Dynamixel interface to Axon  (Read 4731 times)

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Offline AdminTopic starter

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Robotis Dynamixel interface to Axon
« on: December 04, 2008, 05:49:12 AM »
I'm trying to figure out how to interface a Robotis Dynamixel servo to the Axon. I *think* I figured it out, but want someone who has used these servos before to verify just in case.

Step zero, attach power (7V+) from unregulated power bus and ground.

Step one, attach the servo signal line using this schematic (pnp transistor) to Tx and Rx of UART0:

Step two, set Axon baud rate to 1Mbps (0% error at 16MHz! wow!).
uartSetBaudRate(0, 1000000);

Step three, use the rprintf functions that come with the Axon to xmit and receive data.
uart0SendByte(some_value);//send a single byte
temp=uart3GetByte();//get a single character

Step four, use the commands in the Dynamixel datasheet.

Offline JonHylands

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Re: Robotis Dynamixel interface to Axon
« Reply #1 on: December 04, 2008, 06:45:54 AM »
There are basically two ways to do this:

- you use a tristate buffer (or a bus switch) to control which of Tx/Rx is hooked to the bus.
- you hook both the Rx and Tx directly to bus line (short them together), and write the software in such a way as only either the Tx or Rx circuitry is enabled at one time

I use the first technique to hook the bus to an FT-232. I use the second technique to hook the bus directly to an ATmega microcontroller. The software for that, written by my brother Dave, is available on his SVN repository:

The two files are bioloid-uart.c and bioloid-uart.h

Also note - 7 volts is not enough for the AX-12. You need to run it between 9 and 12 volts.

- Jon
« Last Edit: December 04, 2008, 06:47:32 AM by JonHylands »

Offline zephyrus

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Re: Robotis Dynamixel interface to Axon
« Reply #2 on: April 06, 2009, 02:48:31 PM »
Hello Sir,

I will be having 10 Dynamixel soon and an Axon Microcontroller, I dont know what to do yet but i hope this will help me.

One question, did you mean to get the power to the Dynamixel servo from external power supply? or can I get it from Axon?

And if I need the maximum power delivered to the Dynamixel, can I take it from the Axon or its not possible?

Thank you

Offline Webbot

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Re: Robotis Dynamixel interface to Axon
« Reply #3 on: April 06, 2009, 07:04:46 PM »
Are you sure that transistor arrangement will work - it looks over simplified to me? The schematic they recommend is on page 12 of their manual and uses an IO pin to control other gates to connect EITHER Tx OR Rx to the servo data but never both. This is the 'tristate buffer' JonHylands refers to.

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