Buffer Sizing, Stopping, and Triggering

Buffer Sizing, Stopping, and Triggering

The Capture function block "Stop and Trigger" tab (Figure 1) is where you find the options for when to stop collecting, how much to collect, how to trigger, and when to trigger.

The first option to set is the collection mode . Vehicle Spy has 4 options. The Table 1 below lists and describes each mode.

Collection Mode Description

Collect in a circular buffer Captures a buffer of the newest messages. Old messages are discarded to make room for new messages when the buffer is full. Save needs to be clicked or called to save data.

Collect in a one-shot buffer Collects one buffer and saves the data to disk.

Collect before and after trigger expression Captures a number of messages before and after a trigger expression. This is a very handy type of function block because it allows for acquiring data before and after an event.

Collect before and after manual trigger Captures a number of messages before and after a manual trigger. The manual trigger can come from:
Clicking the Trigger button.

Using a Script function block and the Function Block Action - Trigger command.

Tapping an assigned hotkey. (described below)

Table 1: Capture Function Block Collection Modes

All four types of capture function blocks have a Buffer Size option

. For circular buffer and one-shot buffer capture types, this is the only setting to setup. The buffer size indicates the number of messages to collect when the function block runs.

When using a "Collect before and after a trigger expression" type capture there will be an option to specify the trigger expression

. The Fx button opens the Expression Builder to build your trigger expression.

The Post Trigger section configures how information is collected after the trigger expression or manual trigger occurs

. You can choose between capturing a certain number of messages or capturing messages for a specific length of time. The pre-capture is determined by the remaining messages in the buffer. For example, if the buffer size is set to 5000 messages and the post trigger is set to 1000 messages, 4000 messages will be captured before the trigger and 1000 messages will be captured after the trigger.

The last option in the "Stop and Trigger" tab is to set a Hotkey and/or event sound

. Both of these features are optional. The hotkey offers a way to trigger the function block with a keyboard or joystick. The event sound option will play a specified *.WAV file when the function block is triggered. This is an easy way to let the user know that new data is being collected.

Figure 1: The capture function block Stop and Trigger tab.

Last Update: Tuesday, May 11, 2010

Collection Mode	Description
Collect in a circular buffer	Captures a buffer of the newest messages. Old messages are discarded to make room for new messages when the buffer is full. Save needs to be clicked or called to save data.
Collect in a one-shot buffer	Collects one buffer and saves the data to disk.
Collect before and after trigger expression	Captures a number of messages before and after a trigger expression. This is a very handy type of function block because it allows for acquiring data before and after an event.
Collect before and after manual trigger	Captures a number of messages before and after a manual trigger. The manual trigger can come from: Clicking the Trigger button. Using a Script function block and the Function Block Action - Trigger command. Tapping an assigned hotkey. (described below)