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SPEEDBOX / TriggerInput

Trigger Input

There are two trigger inputs available on the SPEEDBOX, one is accessed through the bottom BNC connector on the front panel (trigger 1), and the other is accessed through the expansion connector (trigger 2). Either none, one or both of the triggers may be enabled, and each enabled trigger may have its input type set to any of 4 options - rising edge, falling edge, low level or high level.

Trigger Type

The triggers both have internal pullups on them. Therefore they are in the "high level" state when no switch is physically connected. A switch which connects the inner and outer of the BNC connector together (trigger 1) or connects the trigger pin to the earth pin of the expansion connector (trigger 2) would cause a falling edge when the button is pressed. The following diagram shows the effect of pressing and releasing a button attached to a single one of the trigger inputs:

When the trigger is active, the blue LED on the SPEEDBOX lights to indicate this. When both triggers are enabled, the global trigger active state is set based on the last trigger event received. The initial global trigger active state at startup is set based on the highest numbered enabled trigger. When this is level triggered, it is set based on its level. When this is edge triggered, it is set based on the "start with outputs on" setting in the "Trigger effect" box.

An example of using both triggers is shown below. Both triggers have been enabled. Trigger 1 type has been set to "rising edge to toggle" and trigger 2 type has been set to "high level to activate". Since trigger 2 is the highest numbered enabled trigger the initial global trigger state is active, since this trigger starts at a high level in the example. The first signal received is a falling edge from trigger 1. This is ignored, since trigger 1 is a rising edge trigger. The next signal received is a rising edge from trigger 1. This toggles the global trigger state to be inactive. The next signal to be received is a transition to low level from trigger 2. This has no effect, since the global trigger state is already inactive. The next signal received is a falling edge from trigger 1, which is ignored. The next signal received is a transition to high level from trigger 2. This has the effect of activating the global trigger state. The rest of the signals and their effect can be seen by following the diagram below.

Trigger Effect

The trigger inputs can be set to activate the analogue outputs, the distance pulse output, or both. If the triggers are set to toggle the status on a rising or falling edge, the initial state of the output can be set to on by ticking the “start with outputs (analogue and digital pulse) on” box, if this is not ticked the outputs will be off initially.

It is possible to configure the unit to output high resolution timestamps of the trigger events over either CAN or Serial. Please refer to the CAN configuration or Serial data configuration sections for details on how to configure these messages to be output.

It is also possible to log CAN or serial messages containing distance that is only calculated when the trigger state is active. Over CAN there are two seperate distance messages, one of which outputs continuously integrated distance, and the other which outputs distance only integrated when the trigger is active. Over serial there is a complication in that there is only one Race Technology format distance message available. When neither trigger is enabled, this message will output continuously integrated distance. When either trigger is enabled, this message will output distance only integrated when the trigger state is active. Hence the Race Technology format distance output will always be zero if a trigger is enabled but the state is inactive. If distance output over serial is wanted but triggering is not needed, it is best therefore to disable both triggers.