Control Protocols of Motion Control Devices

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Simplifying Control ProtocolsZaber Technologies


Every motion controller has its own command protocol.

command protocol(n.) series of rules that dictates the format of conversation between you and the motion controller.


The command protocol affects:



How intuitive the controller is to use.




How quickly the controller can communicate.




How quickly the controller can communicate.

The type of device(s) that the controller can communicate with.


Having an open, consistent, easy-to-use protocol is important because...



It makes it easy to integrate devices quickly into an application.



It makes it easy to integrate devices quickly into an application.

It reduces the time it takes for users to become proficient with the controls.


Zaber’s devices use two command protocols.



ASCIIAn easy-to-use and intuitive protocol for communicating in plain text.




BINARYA 6-byte binary protocol designed for relaying commands in a consistent, compact format.


What’s the difference?


Zaber’s A- and X-Series devices can use both Binary and ASCII protocols; T-Series can use just Binary.

ASCIIBINARY


Binary communicates in command numbers. ASCII communicates in plain text.

ASCIIBINARY


Each protocol has its own benefits. Binary is simple, with concise commands. ASCII is easy to use, and it is compatible with many devices. It also offers added support for new features.

ASCIIBINARY


Binary’s simplicity may limit the expandability and complexity of its command list. While ASCII offers ease of use, its commands do not have a consistent length.

ASCIIBINARY


More information about each protocol is available on Zaber’s Support wiki: www.zaber.com/support


Now, let’s focus on each protocol and how you can use them to communicate with your devices.


First, let’s look at Binary.

BINARYA 6-byte binary protocol designed for relaying commands in a consistent, compact format.


BINARY

Every command that is sent and every response that is received back from the controller contains three pieces of information.


Device number executing the command

(1 byte)

BINARY

Multiple devices can be chained in a series. The device number indicates which device in a daisy-chain should respond to the command.



(1 byte)

The number of the command or setting

(1 byte)

BINARY

The number of the command or setting indicates the action being executed.The number of the command or setting indicates the action being executed.



(1 byte)

The number of the command or setting

(1 byte)

A data value (4 bytes)

BINARY

The meaning of the data value will depend on the command.


For example: Let’s say you want to send a command to the first device in the series (device number 1) to find the home position (command number 1).

Command 1: 1, 1, 0, 0, 0, 0


For example: Then, you want to send another command to move forward relative to the current position (command number 21) by 1000 microsteps.

Command 1: 1, 1, 0, 0, 0, 0

Command 2: 1, 21, 232, 3, 0, 0


In the first command, the data value is 0 because the home command does not require any additional information to run.

Command 1: 1, 1, 0, 0, 0, 0

Command 2: 1, 21, 232, 3, 0, 0


In the second command, the four data bytes are arranged in order of least significant byte to most significant byte. Software is usually used to handle the data conversion.

Command 1: 1, 1, 0, 0, 0, 0

Command 2: 1, 21, 232, 3, 0, 0


Each time a command completes, the controller will send back a response in the same format.

Command to device 1, 1, 0, 0, 0, 0...stage retracts to home...

Response from device 1, 1, 0, 0, 0, 0


Now, let’s look at ASCII.



Plain text commands

ASCII

The ASCII protocol is available on Zaber’s A-Series devices with firmware version 6.06, and all X-Series devices. ASCII allows for plain text communication between a computer and a controller.


For example: Let’s say you want to command a device to move to a position 1000 microsteps forward from the current position.

Command 1: /move rel 1000 9


For example: Then, let’s say you want to command the device to find the reference position.

Command 1: /move rel 1000

Command 2: /home9

9


The controller will respond, letting you know that the command has been received and that it will be executed, or that the command has been rejected and why.

Command to device /01 home

Response from device @01 1 OK IDLE -- 0...device begins to move...

9

9


Simple, right?



Besides simplicity, there are a number of benefits to this protocol.


It’s simple to use because it’s text-based and designed for readability.



It’s easy for new users to be able to pick up the communication quickly.



It’s easy for new users to be able to pick up the communication quickly.

Using ASCII characters for control allows compatibility with a wide variety of devices, like PLCs (programmable logic controllers).


Faster communication speeds are supported, which allows for further compatibility.


Faster communication speeds are supported, which allows for further compatibility.

Added support for new features and commands, such as multiple limits, programmable actions, and I/Os.


Now that we know what these protocols are, how do we use them?


Software, such as our free, open-source Zaber Console, facilitates the use of these protocols on our positioners.

ASCII

Binary


Other programs, such as LabVIEW, can also be used. Zaber offers LabVIEW drivers for controlling devices with ASCII or Binary protocol.

ASCII

Binary


Visit www.zaber.com/software or email [email protected] for more information.

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Control Protocols of Motion Control Devices