# Command String

Command String is a string which external devices send to vision application requesting one task or multiple tasks be executed, it is composed of three parts: Command Key, EncodedID and optional parameters.

### Command Key

Command key indicates the type of action that a vision task has to perform. For example, the hand-eye calibration task can be started, continued or completed by sending a suitable command key. Similarly a task that finds the features on a part can be executed to perform train-time or run-time actions through a suitable command key.

Here are the most frequently used command keys in AlignPlus:

CommandKey | Description | When to use
--- | --- | ---
ACB | Auto Calibration Begins | Vision Guided Hand-eye Calibration
AC | Auto Calibration
HEB | Hand-eye Calibration Begins | Motion Guided Hand-eye Calibration
HE | Hand-eye Calibration
HEE | Hand-eye Calibration Ends
IC | Intrinsic Calibration | Checkerboard Calibration, Cross Calibration or Manual Calibration
TA | Train Alignment. Registers the golden pose of the target. | Train Time Commands
TT | Train VGR step (register target, single or multiply shots)
TTR | Train VGR step (register robot pick/place position for a target)
LF | Locate Features | Feature Finding in run time.
GP | Get Pose | Pose Computing
LFA | Locate Features Asynchronously | Feature Finding in run time in asynchronous mode
GPA | Get Pose Asynchronously | Pose Computing in asynchronous mode
LFGP | First run Locate Feature, second run Get Pose | Feature Finding and Pose Computer in run time
MEA | Measure | Run inspection
MEAA | Measure Asynchronously | Run inspection asynchronously
LFMEA | Locate Features, then Measure | Run feature finding first, then run inspection
MGP | Multi-part Get Pose | Multi-part pose computation
MGPA | Multi-part Get Pose Asynchronously | Run multi-part pose computation
LFMGP | Locate Featues, then run Multi-part Get Pose | Run feature finding first, then run multi-part pose computation synchronously

### Parameters

Some commands require additional parameters from the PLC. For example, applications such as LF, or GP require the current pose of the alignment device to execute correctly. These additional parameters are encoded in the command string.