AX-12's and RX-64's on the same communications string.
AX-12's and RX-64's on the same communications string.
by sap1975
Sun Aug 09, 2009 6:28 pm
Hi Guys (and girls possibly)
I’m new here and was wondering if you could help me out.
The short version of the question would be if anyone knows if it’s possible to run RX-64’s and AX-12+’s on the same line. Have any of you guys done it. What do i need to be careful of?
Having said that i know that the power requirements for the RX-64 are different from that of the AX-12+ so it would require two separate “power” lines. Also i as far as i can tell the RX series uses a differential signal line but that should be sortable as well. (I think i saw a schematic outlined for that in the RX-64’s manual)
A couple of words on the project.
I’ve got a thing for industrial robots (don’t ask why) but since there monumentally expensive, large and heavy actually going out and getting one is out of the question.
So… i have been pondering on building a model for quite some time now. And started doing some research on RC-Servos when i came across the Bioloid. Well lets put it this way my eyes lit up like a Christmas tree when i started reading the manuals.
Anyways… the plan was to use AX-12’s for the four axis carrying the least load and two RX-64’s for the two axis that carry the master load and hocking up the lot to a computer using the USB2DYNAMIXEL interface.
I included a drawing of the first mockup i did just to get a rough placement of the servos.
It’s based on a Fanuc LR-Mate.
Kindest Regards
Stig.
I’m new here and was wondering if you could help me out.
The short version of the question would be if anyone knows if it’s possible to run RX-64’s and AX-12+’s on the same line. Have any of you guys done it. What do i need to be careful of?
Having said that i know that the power requirements for the RX-64 are different from that of the AX-12+ so it would require two separate “power” lines. Also i as far as i can tell the RX series uses a differential signal line but that should be sortable as well. (I think i saw a schematic outlined for that in the RX-64’s manual)
A couple of words on the project.
I’ve got a thing for industrial robots (don’t ask why) but since there monumentally expensive, large and heavy actually going out and getting one is out of the question.
So… i have been pondering on building a model for quite some time now. And started doing some research on RC-Servos when i came across the Bioloid. Well lets put it this way my eyes lit up like a Christmas tree when i started reading the manuals.
Anyways… the plan was to use AX-12’s for the four axis carrying the least load and two RX-64’s for the two axis that carry the master load and hocking up the lot to a computer using the USB2DYNAMIXEL interface.
I included a drawing of the first mockup i did just to get a rough placement of the servos.
It’s based on a Fanuc LR-Mate.
Kindest Regards
Stig.
Re: AX-12's and RX-64's on the same communications string.
by RandomMatt
Sun Aug 09, 2009 10:32 pm
sap1975 wrote:The short version of the question would be if anyone knows if it’s possible to run RX-64’s and AX-12+’s on the same line.
It should be possible...
sap1975 wrote:Have any of you guys done it.
not me
But, I have read the manuals for the RX (and DX) series of servos.sap1975 wrote:What do i need to be careful of?
The commands are the same on both the AX and RX (and DX) buses. So you need to make sure that you don't reuse IDs.
Secondly, you need to think why you are doing it - given that you have two separate physical buses (The two wire RS485 and the one wire TTL) - are you sure that you want to tie them together? The only reason I can think of is so that you can use a single SYNCWRITE packet to both types of servos
Thirdly, you probably want to use the same controller for both buses (assuming that do choose to treat them as one). With a little effort you could modify a CM5 to talk RX (RS485) as well as AX (TTL). PORT E2 is high when TX is enabled, PORT E3 is high when RX is enabled.
by sap1975
Mon Aug 10, 2009 7:49 am
Hi Matt
Thanks for sharing.
The reason i want to tie the two busses together is for simplicity.
I know it sounds a bit weird adding an additional piece of “custom” hardware for simplicities sake but if they’re tied to the “same” bus it’s easier to in my book anyway to read and write to/from them from a software point of view.
I’ll have to look into the CM5. Haven’t read the manual yet
it might be interesting just to get started.
Off topic: It puzzles me that the use of the robotis “rotary actuators” are not more wide spread in other areas of hobby and educational robotics. The possibilities seems virtually endless. Especially with the parts from HUV.
I know for a fact that i can’t build a “servo” with that kind of torque, speed and precision for the cost of an AX-12.
+ Not having to deal with the pwm thing of the older type servos seems great.
/Stig
Thanks for sharing.
The reason i want to tie the two busses together is for simplicity.
I know it sounds a bit weird adding an additional piece of “custom” hardware for simplicities sake but if they’re tied to the “same” bus it’s easier to in my book anyway to read and write to/from them from a software point of view.
I’ll have to look into the CM5. Haven’t read the manual yet
it might be interesting just to get started.
Off topic: It puzzles me that the use of the robotis “rotary actuators” are not more wide spread in other areas of hobby and educational robotics. The possibilities seems virtually endless. Especially with the parts from HUV.
I know for a fact that i can’t build a “servo” with that kind of torque, speed and precision for the cost of an AX-12.
+ Not having to deal with the pwm thing of the older type servos seems great.
/Stig
by Tyberius
Mon Aug 10, 2009 5:03 pm
limor wrote:i'm not sure about this but what would happen if you plug both AX and DX components into a USB2Dynamixel?
i'll ask the guys at robotis..
Can only do one or the other: There is a slider switch to choose which communication protocol to use.
To OP: This could also be done with the same bus and a level shifter, granted that you take into account for the half duplex vs full duplex. I believe Jon Hylands did something similar to this in one of his projects.
by limor
Tue Aug 11, 2009 10:38 pm
Tyberius wrote:limor wrote:i'm not sure about this but what would happen if you plug both AX and DX components into a USB2Dynamixel?
i'll ask the guys at robotis..
Can only do one or the other: There is a slider switch to choose which communication protocol to use.
yes, thats the answer i got from Robotis. no special tricks to allow both types of servos at the same time using USB2Dynamixel..
by PedroR
Wed Aug 12, 2009 12:51 pm
From what I know, the RX series is also half duplex.
Although it has two wires they are used as the RS485 differential pair.
In TTL the signals level are in reference to ground whereas in RS485 they have a pair (positive) and are in reference to this same differential pair.
FOr full Duplex, in TTL you need only 2 wires+ GND (RX and TX, which in turn are high and low in reference to ground) whereas in RS485 you need 4 wires (1 differential pair for RX and 1 differential pair for TX).
What was explained to me is that in theory the use of differential pairs offers more robust and reliable communications and more resistance to noise.
If you are looking for a solution out of the box that mixes RS485 and TTL I would suggest the CM2 controller form Robotis.
It is not highly optimized for TTL (AX series) signals but it is indeed able to mix both AX series and RX series in the same bus and in practice it does seem to work.
Although it has two wires they are used as the RS485 differential pair.
In TTL the signals level are in reference to ground whereas in RS485 they have a pair (positive) and are in reference to this same differential pair.
FOr full Duplex, in TTL you need only 2 wires+ GND (RX and TX, which in turn are high and low in reference to ground) whereas in RS485 you need 4 wires (1 differential pair for RX and 1 differential pair for TX).
What was explained to me is that in theory the use of differential pairs offers more robust and reliable communications and more resistance to noise.
If you are looking for a solution out of the box that mixes RS485 and TTL I would suggest the CM2 controller form Robotis.
It is not highly optimized for TTL (AX series) signals but it is indeed able to mix both AX series and RX series in the same bus and in practice it does seem to work.
by sap1975
Wed Aug 12, 2009 6:06 pm
PedroR wrote:It is not highly optimized for TTL (AX series) signals but it is indeed able to mix both AX series and RX series in the same bus and in practice it does seem to work.
In that case it seems i have found what i’m looking for. Thanks to you i might add
I just went over the manual for the CM-2 and although there are references to the AX-12 it seems to me that it’s made up of bits and pieces from the CM-5 and various Dynamixel manuals. The references might not be intentional.
So just for the lame… You hooked it up and saw it working?
(would just love to be sure before i spend the better part of 700£)
/Stig.
by PedroR
Thu Aug 13, 2009 10:04 am
Hi Stig
I did see one CM2 working with both AX 12 and RX series servos.
I can check with the manufacturer because they told me the, when they designed it, what they had in mind was to use the AX connector on the CM2 the AX -S1 sensor and not really AX servos (nevertheless the bus is the same)
They told me that people have been using the AX connector on the CM2 with AX servos as well (mixing AX and RX series servos) and it performs well.
As I mentioned I did see a sample working with AX+12 + RX-10 + RX-28 + RX-64, all connected to the same CM2 board and they worked nicely.
I will send an email to the manufacturer and double check if there is any known limitation.
I did see one CM2 working with both AX 12 and RX series servos.
I can check with the manufacturer because they told me the, when they designed it, what they had in mind was to use the AX connector on the CM2 the AX -S1 sensor and not really AX servos (nevertheless the bus is the same)
They told me that people have been using the AX connector on the CM2 with AX servos as well (mixing AX and RX series servos) and it performs well.
As I mentioned I did see a sample working with AX+12 + RX-10 + RX-28 + RX-64, all connected to the same CM2 board and they worked nicely.
I will send an email to the manufacturer and double check if there is any known limitation.
by PedroR
Thu Aug 13, 2009 3:53 pm
Hi Stig
After confirming with the manufacturer, indeed you can use an AX-12 with the CM2 BUT it is not an optimal scenario.
Here is their reply:
"Manual of CM-2+ (Page 5) says as following.
The Dynamixel motor series, DX-113, DX-117, RX-28, and RX-64 link
to the AX-S1, a Dynamixel sensor, allowing you to edit the motion of robot,
create a behavior control program, and program in C language.
And in page 15, address of AX-S1 can be allocated to 100~109.
It means that it’s hard to mix up AX-12+ and RX series
to make intelligent robot.
Some of users tries to attach AX-12+ to AX-S1 address,
but feedback information can be transmitted either TTL / RS-485
so simultaneous motion control might be impossible.
Please tell your customer to wait for CM-700 to come. "
In fact I know of a new CM-700 controller that is meant to replace the CM-2.
However I must add the release date is not defined and looking at Robotis product development cycle it could still be months away...
So I guess it really depends on your schedule.
It is possible to attach AX 12s to CM2 (I saw it working and the docs say it would work as long as you use ID 100~109) but simultaneous control and mixing packets of RX and AX at the same time may be hard - but not impossible.
--
Another suggestion I'd like to make as an alternative to CM-2 is using two USB2Dynamixel adapters:
- On one adapter you would be talking on RS485 to the RX series servos.
- On the other adapter you would be talking on TTL to the AX servos.
Since you'll be using a full PC I guess it should be fairly easy to coordinate the communication.
After confirming with the manufacturer, indeed you can use an AX-12 with the CM2 BUT it is not an optimal scenario.
Here is their reply:
"Manual of CM-2+ (Page 5) says as following.
The Dynamixel motor series, DX-113, DX-117, RX-28, and RX-64 link
to the AX-S1, a Dynamixel sensor, allowing you to edit the motion of robot,
create a behavior control program, and program in C language.
And in page 15, address of AX-S1 can be allocated to 100~109.
It means that it’s hard to mix up AX-12+ and RX series
to make intelligent robot.
Some of users tries to attach AX-12+ to AX-S1 address,
but feedback information can be transmitted either TTL / RS-485
so simultaneous motion control might be impossible.
Please tell your customer to wait for CM-700 to come. "
In fact I know of a new CM-700 controller that is meant to replace the CM-2.
However I must add the release date is not defined and looking at Robotis product development cycle it could still be months away...
So I guess it really depends on your schedule.
It is possible to attach AX 12s to CM2 (I saw it working and the docs say it would work as long as you use ID 100~109) but simultaneous control and mixing packets of RX and AX at the same time may be hard - but not impossible.
--
Another suggestion I'd like to make as an alternative to CM-2 is using two USB2Dynamixel adapters:
- On one adapter you would be talking on RS485 to the RX series servos.
- On the other adapter you would be talking on TTL to the AX servos.
Since you'll be using a full PC I guess it should be fairly easy to coordinate the communication.
by sap1975
Thu Aug 13, 2009 7:15 pm
Hi Pedro
Thanks a bunch for going into this so vigorously.
These where exactly the answers i was looking for so things almost couldn’t be better.
At this time the project is still in the “research” phase so waiting for the CM-700 is a definite possibility. Alternately i just might go ahead and design/build a converter allowing both signals on the same port by simply converting the differential signal to ttl.
Regarding just using two USB2Dynamixel`s i would like to avoid doing that since it would mean that i have to access two com ports instead of just the one.
I would also like to add that during my search for components i still haven’t found anything that comes close to this system regarding ease of use, power and cost.
I will without a doubt be going for the Robotis system.
Time to do some inertia calculations
While i have you here “so to speak” do you know if any extended specifications exists for the servos?
Thanks again. I really do appreciate it.
/Stig
Thanks a bunch for going into this so vigorously.
These where exactly the answers i was looking for so things almost couldn’t be better.
At this time the project is still in the “research” phase so waiting for the CM-700 is a definite possibility. Alternately i just might go ahead and design/build a converter allowing both signals on the same port by simply converting the differential signal to ttl.
Regarding just using two USB2Dynamixel`s i would like to avoid doing that since it would mean that i have to access two com ports instead of just the one.
I would also like to add that during my search for components i still haven’t found anything that comes close to this system regarding ease of use, power and cost.
I will without a doubt be going for the Robotis system.
Time to do some inertia calculations
While i have you here “so to speak” do you know if any extended specifications exists for the servos?
Thanks again. I really do appreciate it.
/Stig
by PedroR
Fri Aug 14, 2009 12:35 pm
Hi stig
With regards to waiting for the CM700 it really depends on your schedule. I would bet on it not being released during this year (only next yr).
Robotis never commits on a release schedule. They do commit on releasing a mature product by the time they release but if it takes time they'll just wait....
With regards to extended specs, the only thing we know about currently are the servo spec sheets that you can download form the Robotis website.
The most up to date specs can be found in their download section.
With regards to waiting for the CM700 it really depends on your schedule. I would bet on it not being released during this year (only next yr).
Robotis never commits on a release schedule. They do commit on releasing a mature product by the time they release but if it takes time they'll just wait....
With regards to extended specs, the only thing we know about currently are the servo spec sheets that you can download form the Robotis website.
The most up to date specs can be found in their download section.
by Robo1
Sat Aug 15, 2009 9:02 pm
Hi
I've had a lot of experiance with dx117 which is the same communication method as the rx's. If I was you, I would build a simple circuit with the Rx,Tx going in and a selector pin. set it high and use the AX circuit low use the RX curcuit. it would be a very simple circuit with two chips one for the rs485 and the over for the selector.
just my thoughts.
Bren
I've had a lot of experiance with dx117 which is the same communication method as the rx's. If I was you, I would build a simple circuit with the Rx,Tx going in and a selector pin. set it high and use the AX circuit low use the RX curcuit. it would be a very simple circuit with two chips one for the rs485 and the over for the selector.
just my thoughts.
Bren