Script Type Function Block Commands: Start Loop and End Loop

Overview

The Start Loop and End Loop commands are used to create loops, which are blocks of commands that are executed a specified number of times. The repetition count can either be a constant value, or one computed from an expression based on signal values and other data.

These commands must be entered in matched pairs, one End Loop for every Start Loop.

Start Loop Command

Each loop begins with a Start Loop command. The Valuefield for this command specifies the number of times the loop will be repeated:

Constant Loop Counter: After the Start Loopcommand is selected, a default value of 1 will appear in its Valuecolumn field. Change this to the number of times you want the loop to run.
Dynamic Loop Counter: Edit the Value cell, then press the = key twice to launch the Expression Builder. Enter an expression, and the loop will run a number of times equal to the value that the expression returns.

When the script is run, the loop counter will be shown updating in real time in the Value cell of the Start Loop command; it decrements from the start value down to 1 as the loop proceeds. This progression may or may not be visible, depending on how quickly the loop executes.

Note: After selecting the Start Loop command, Vehicle Spy will display it in the script as Start a loop. These are equivalent.

End Loop Command

The End Loop command marks the end of the loop. It has no parameters.

Note: After selecting the End Loop command, Vehicle Spy will display it in the script as End the last loop. These are equivalent.

Examples

Here are two examples showing typical uses of loops.

Loop with Constant Loop Counter

The example in Figure 1 shows a simple script that transmits a message exactly 7 times each time it runs.

Figure 1: A simple loop with a constant loop counter.

Loop with Expression-Derived Loop Counter

Figure 2 shows a script that waits for the receipt of a message calledCAN Control Message 1. This message contains a signal, Number of Transmissions, which dictates how often the loop runs, and thus how often CAN Message A is transmitted.