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View Full Version : Dynamixel AX-12 - Resetting Baud Rate?



MaelXD
07-20-2013, 03:19 AM
Dynamixel Lesson 1: Do not accidentaly set the Baud Rate Register to 0x00. Especially if you do not have a USB2Dynamixel to re-flash firmware with...

More seriously, is it possible to re-flash the Dynamixel firmware without using the USB2Dynamixel?
I have it connected to an FPGA and I can happily send it any signalling standard or data rate, but I haven't seen the spec for re-flashing images anywhere.

Otherwise, I suppose I'll order a USB2Dynamixel.

jwatte
07-20-2013, 03:04 PM
The safest thing to do is to keep a USB2Dynamixel around. Or a USB2AX.

The protocol between Dynamixel Wizard (which does recovery) and the USB2Dxl is not that complex (and looks a lot like the servo protocol,) so if you have something else that can speak that protocol on USB and the UART protocol on the TTL bus, you might be able to make one yourself.

AFAICT, the firmware recovery mechanism works by the servo always probing at/looking for a particular speed on start-up, so if the USB2Dxl is continually sending the "firmware recovery" packet at that speed (57600 bps?) then the servo will start downloading firmware instead of going to its normal operating mode.

Finally, 0x00 is a fine value for the baud rate register. It means 2 Mbps. I use it to talk to all my servos. An Arduino or other similar embedded device can talk at that speed just fine. You could use this to re-write the baud rate register back to where you want it, without re-flashing the firmware. Also, the USB2Dxl can talk at 2 Mbps, so it, too, can just change the register rather than needing to recover firmware.

Th232
07-20-2013, 10:22 PM
Finally, 0x00 is a fine value for the baud rate register. It means 2 Mbps. I use it to talk to all my servos. An Arduino or other similar embedded device can talk at that speed just fine. You could use this to re-write the baud rate register back to where you want it, without re-flashing the firmware. Also, the USB2Dxl can talk at 2 Mbps, so it, too, can just change the register rather than needing to recover firmware.

Isn't the maximum for the AX and RX series 1 MBps though?

jwatte
07-21-2013, 12:52 AM
Dunno. Try talking to them at 2 Mbps and see what happens?

MaelXD
07-22-2013, 03:47 AM
I did try using it at 2Mbps and I didn't find it being very responsive. But I might have another go in a bit.

siempre.aprendiendo
07-22-2013, 07:00 AM
What Robotis says is:

Communication Speed : 7343bps ~ 1 Mbps

http://support.robotis.com/en/product/dynamixel/ax_series/dxl_ax_actuator.htm