RoboSavvy Forum

Dynamixel Instruction

2007-09-20T11:20:46+01:00

The main difference is you can set the position and speed of all the servos on your bus with one instruction. If you're trying to run at 30 Hz, and you've got 20 servos, you're looking at 600 instructions per second using REG_WRITE and ACTION, versus 30 instructions per second using SYNC_WRITE.

Plus, unless you turn off the response mode of your servos, you also have to wait for a response from each of those 600 commands before you can send the next.

Ideally, you need the time to actually read values from the servos. A single SYNC_READ followed by a set of READ_DATA instructions is much simpler.

- Jon

Statistics: Posted by JonHylands — Thu Sep 20, 2007 11:20 am

instruction

2007-09-20T07:28:23+01:00

JonHylands wrote:
I use SYNC_WRITE constantly with all my Bioloid stuff. All the walk sequences of MicroRaptor and BrainBot are all done strictly with SYNC_WRITE.
- Jon

I am still curious about what exactly the difference between SYNC_WRITE and REG_WR +ACTION?

cheers

ryann2k1

Statistics: Posted by ryann2k1 — Thu Sep 20, 2007 7:28 am

Instruction...

2007-09-15T04:37:02+01:00

yep...
I might need to rework the built-in gaits in motion editor.
Thanks Jon..

cheers,

ryann2k1

Statistics: Posted by ryann2k1 — Sat Sep 15, 2007 4:37 am

Dynamixel Instruction

2007-09-14T14:13:50+01:00

I don't know - I never tried to use any of the built-in gaits. It may be a timing thing - I guess it depends on how the gaits are stored. If they are only storing keyframes, and dynamically generating in between, then it wouldn't surprise me that they wouldn't work.

In my system, I set up keyframes, and then statically generate all the in-between frames, so that it runs at an even 30 frames per second. If I want to tweak something, I just go back to the keyframes, make the changes there, and re-generate the in-betweens.

- Jon

Statistics: Posted by JonHylands — Fri Sep 14, 2007 2:13 pm

Instruction

2007-09-14T14:06:19+01:00

It is strange.. I have managed to send the parameter all at once, but still the gaits generated from motion editor can not be used in C style.(especially for page 11 and page 13, wake up pose)
I wondering what is the problem

ryann2k1

Statistics: Posted by ryann2k1 — Fri Sep 14, 2007 2:06 pm

Instruction

2007-09-14T13:13:24+01:00

Yes Jon,
Now, I manage to use REG_WRITE + ACTION
Still thinking how to use SYNC_WRITE since all parameters must be in one line.
Thanks Jon,

Cheers,

ryann2k1

Statistics: Posted by ryann2k1 — Fri Sep 14, 2007 1:13 pm

Dynamixel Instruction

2007-09-14T12:48:26+01:00

I use SYNC_WRITE constantly with all my Bioloid stuff. All the walk sequences of MicroRaptor and BrainBot are all done strictly with SYNC_WRITE.

I call SYNC_WRITE about 30 times per second, to set the position and speed values of 20 servos at the same time. I do this through my USB bus interface from my PC - I don't use the CM-5 at all.

Is that what you were asking?

I have a SYNC_WRITE command object, which gets a collection of devices. It asks each device for its desired position and desired speed, and then builds up a command array of bytes to send. It also knows how to add the prefix bytes and the checksum. This is all written in Squeak Smalltalk.

- Jon

Statistics: Posted by JonHylands — Fri Sep 14, 2007 12:48 pm

Dynamixel Instruction

2007-09-14T11:55:14+01:00

JonHylands wrote:
The thing to do then is to remove 2 or 3 servos, and have then hooked up on the bench, but not connected to each other mechanically, so they can all swing freely throughout their 300 degree limits.

Then you can play until you get the commands right...

- Jon

I only manage to use them in controlling my servos directly via Robot Terminal. Still find it difficult in implenting in C. Did you manage to use them?

cheers,

ryann2k1

Statistics: Posted by ryann2k1 — Fri Sep 14, 2007 11:55 am

Instruction

2007-09-14T05:13:13+01:00

Thank you Jon,

cheers

ryann2k1

Statistics: Posted by ryann2k1 — Fri Sep 14, 2007 5:13 am

Dynamixel Instruction

2007-09-14T05:01:08+01:00

The thing to do then is to remove 2 or 3 servos, and have then hooked up on the bench, but not connected to each other mechanically, so they can all swing freely throughout their 300 degree limits.

Then you can play until you get the commands right...

- Jon

Statistics: Posted by JonHylands — Fri Sep 14, 2007 5:01 am

instruction

2007-09-14T03:51:27+01:00

I have read page 23 in AX-12 manual.
I'm not sure to implement since it is already integrated in libCM5.lib
I'm just trying to use the correct syntax since sometimes wrong command can make wrong motion to each motors. I'm worried to make my servos broken.
Thank you guys.

cheers,

ryann2k1

Statistics: Posted by ryann2k1 — Fri Sep 14, 2007 3:51 am

Dynamixel Instruction

2007-09-14T03:02:54+01:00

The AX-12 Manual
page 23 has an excellent sync_write example.

Statistics: Posted by Bullit — Fri Sep 14, 2007 3:02 am

Dynamixel Instruction

2007-09-14T02:57:53+01:00

SYNC_WRITE is designed to update any number of servos with different values, and you can set both the speed and position of each servo independently with only one command.

- Jon

Statistics: Posted by JonHylands — Fri Sep 14, 2007 2:57 am

Dynamixel Instruction

2007-09-14T02:18:35+01:00

Hi guys,

JonHylands wrote:
I've never tried those commands - SYNC_WRITE is much better...

- Jon

for example Id 1
writeword(1, P_GOAL_POSITION_L, 235)
how to implement sync_write for 18 servos with different values?

cheers,

ryann2k1

Statistics: Posted by ryann2k1 — Fri Sep 14, 2007 2:18 am

Dynamixel Instruction

2007-09-13T22:22:31+01:00

I've tried both but Jon is right the sync _write is better.
From C there is much more to consider then just having the servos start at the same time. They need to end at the same time too. Point to point motion. Each servo may have a different distance to travel but yet they should all finish the motion together and maintain torque along the way. The way the bioloid firmware accomplishes this is by generating s-curves in between each pose. This is critical for smooth motion.

Statistics: Posted by Bullit — Thu Sep 13, 2007 10:22 pm