Yaskawa servo options

The options are analogue OR pulse (== step direction)

Both work well, there really isn't much to choose between them.

EtherCAT is very nice too. I have Omron G5 EtherCAT drives running under LinuxCNC.

Pros:
* Very simple cabling - just plug in a CAT5/6/7 cable.
* Galvanic isolation between computer and drives.
* My EtherCAT drives have generic IO:s, so no further IO board needed. This includes functions to latch encoder position on rising edge, for tool height setting and edge finding.
* All loops closed in the drives, and you can feed-forward velocity and acceleration as well as the position reference to the drives.
* Possible to read back multiple values (besides encoder position), like control effort.

Cons:
* Lots of manual reading to do to set up things the correct way, especially if you need to use the generic LinuxCNC driver. You pretty much need to become an expert on the EtherCAT protocol - it can get pretty frustrating. Make sure to find and read the manual for the drive first, before you buy, so you know what's in store. You *will* need to read up on PDO mappings and such. (As far as I know there is no special driver for Yaskawa EtherCAT drives in the etherlab package for LinuxCNC, but if you are a programmer you should be able to modify the Omron G5 one which would probably be easier than using the generic driver.)

I would absolutely go for EtherCAT if I had the choice!

You would really suggest ethercat to someone that is so new he is asking about the difference between analog, pulse and step and dir?

No, I cannot choose for him/her. But I can point to EtherCAT as a possibility so he/she can make an informed choice. That's why I also explained the cons in my post and pointed out reading the manual before taking this path.

Besides, with EtherCAT you don't need to know the difference between analog and step/dir. Steejans will have a lot of reading to do regardless of choice.

One thing that maybe I should have made more clear is that with EtherCAT, you will not find nearly as much help on the forums, since analog and step/dir is much more common. So again, read the manuals, forum etc and make sure that you're comfortable with taking that route before buying anything. That said, I had no knowledge of EtherCAT before, and managed to read up on it (using the Servo Drive manual and this forum) and get it working on my own, so it IS possible.

arvidb wrote: No, I cannot choose for him/her. But I can point to EtherCAT as a possibility so he/she can make an informed choice. That's why I also explained the cons in my post and pointed out reading the manual before taking this path.

Besides, with EtherCAT you don't need to know the difference between analog and step/dir. Steejans will have a lot of reading to do regardless of choice.

One thing that maybe I should have made more clear is that with EtherCAT, you will not find nearly as much help on the forums, since analog and step/dir is much more common. So again, read the manuals, forum etc and make sure that you're comfortable with taking that route before buying anything. That said, I had no knowledge of EtherCAT before, and managed to read up on it (using the Servo Drive manual and this forum) and get it working on my own, so it IS possible.

Is the ethercat realtime HAL driver up to date or did you roll your own?

I modified the existing Omron G5 driver in the linuxcnc-ethercat package to support my drive models (by simply adding the correct device ID:s). My modifications have since been accepted upstream so they are now in the package.

I have also experimented with running a drive in velocity mode using halrun, based on the generic EtherCAT driver from the same package. It worked well if I remember correctly.

Basically what's needed to run a drive with the generic driver is to write an EtherCAT description .xml file that tells the generic driver how to find the drive on the bus, how to configure it, what data to send and receive, and how to map the data to hal pins.

Edit: The specific drivers in the linuxcnc-ethercat package can be thought of as a convenience layer that lets you ignore things like specific device ID:s, PDO/SDO addresses, watchdog settings and such. The Omron G5 driver configures the servo drive for basic position control; if you want to do more advanced stuff (like feed-forward of velocity, or just run the drive in velocity mode) then you need to set it up using the generic driver.