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extra zeros in status packet and dropped 0xFF byte

조회 수 1000 추천 수 0 2010.08.14 04:01:44
MTR *.83.81.178

I was working with AX-12 servos, and my communications worked perfectly with no problems at all. When I switched to RX-24F and RX-28 servos, the status packet was framed by 0x00 at each end. (Is this normal?) I've also had problems with the RX-24F/28 dropping one of the 0xFF header bytes occasionally. The rest of the packet bytes and checksum are always correct, so this isn't some random signal corruption. I've tested using Python, C code, and a terminal program, under Windows and Linux, and I've been using USB2Dynamixel as well as separate USB/TTL (for AX-12) and USB/RS485 (for RX-**) adapters; all setups show the same results. Also, the Dynamixel Manager finds the AX-12 immediately but fails to find the others (probably because of the extra zeros in the status packet).  Any suggestions??

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[레벨:30]ROBOTIS

2010.08.17 16:29:54
*.112.9.210

Hi MTR,

 

The dynamixel manager is the old version and can not be used to search the new dynamixels.

Please try using the Dynamixel Wizard in the RoboPlus.

 

From the information you have posted, there may be a problem with the chip in the Dynamixel (RX) or MAX485 (USB2DXL).

Of course, not all of them would have this problem. It could be just one. Also, check if there are duplicate IDs.

 

ROBOTIS

 

MTR

2010.08.18 05:13:07
*.83.81.178

Thanks for the suggestion. I just tried Dynamixel Wizard with the same result: it recognizes the AX-12 immediately, but not the other servos. BTW, I've tried one RX-24F and two RX-28's.  All have id 1, but I only connect one at a time. I've tried two USB2Dynamixels, plus custom cables. All setups work, except for the strange packet structure I described.

[레벨:30]ROBOTIS

2010.08.18 18:06:54
*.112.9.210

Hi again MTR!

 

Can you make sure the USB2Dynamixel switch is set to RS485?

Also, try restoring the Dynamixel’s  firmware and let us know how things turn out.

http://support.robotis.com/en/techsupport_eng.htm#software/roboplus/dynamixel_monitor/firmwaremanagement/dynamixel_monitor_fwrecovery.htm

 

ROBOTIS

MTR

2010.08.19 02:33:47
*.83.81.178

The USB2Dynamixel was switched properly. Looks like the problem had to do with termination impedance of the 485 bus. I was using a small resistor to reduce the chances of reflections. Removing the resistor fixed the problem. Do the Dynamixels have built-in termination?

[레벨:30]ROBOTIS

2010.08.23 09:44:03
*.112.9.210

Hi MTR,

 

I'm afraid the Dynamixels do not have built in termination.

 

ROBOTIS

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