Communication between ASCII USB device and CompactLogix

I have an existing machine running a 1768-L45 CompactLogix and the client wants to add linear actuators (http://www.ealingcatalog.com/motion-control/actuators-adjusters/encoderdriver-actuators.html), but the motion controller that they are using is USB. It has an ASCII command set, and I am able to control and monitor the actuators using a virtual COM port and RealTerm.

My question is -- what is the best way to set up communication between my PLC and this device? If I use a USB to Ethernet gateway, will message instructions work to send/receive commands? Is there a better option out there to communicate between USB and PLC?

Get a USB to serial converter and hook up to the serial port of the L45.

I am able to control and monitor the actuators using a virtual COM port and RealTerm.

Click to expand...

So you're plugging in your computer to the actuator, and the actuator is appearing as a Windows COM port. Is that correct ?

Post as much information as you can about the chipset or identity of what's inside that actuator. Windows Device Manager should tell you the basics.

In general, a device that works as a USB adapter doesn't also work as a USB Host. Plugging a USB/Serial converter or USB/Ethernet converter into it might work, or might not. Those devices typically need a USB Host, with drivers written for PC operating systems like Windows and Linux and OSX.

The actuator connects to a controller through a 10 pin port, and the controller is connected to the PC through USB. I believe the drivers included with the controller setup the virtual COM port.

I've attached a screenshot of the basic information from the Device Manager. There are also a bunch of properties with long alphanumeric values under "Details" -- let me know if any of these would be useful to look at.

The good news is that they have an FTDI chipset, so the serial port support by PC operating systems should be broad (I'm thinking embedded Linux).

The bad news is that it's not an HID (keyboard/mouse) or Printer type device, which could be interfaced with by the RTA Automation USB/A-B gateway.

http://www.rtaautomation.com/product/435usb/

It's worth a call to RTA to see if they are working on something that would do this job.

If you had a PC connected to the servo, you could use com0com or another null modem emulator to connect the CompactLogix serial port to the servo driver USB COM port. There are probably similar approaches using socom or tty0tty for Linux.

I did look into the RTA gateway, they said there's "a chance" it will work.

I do have a PC connected to this machine, so I think I will explore this route further. I will definitely look into com0com, or probably there are some other ways I can make it work that way, maybe through an OPC server.

Thanks for your help Ken!