Point Grey Flea3 USB 3.0 Technical Reference 6 Image Acquisition
Ensuring Trigger is Armed
It is possible for the camera to be in asynchronous trigger mode but not be ready to accept a trigger. The reason is the
camera may be currently exposing an image; the camera is only ready to be triggered again when this image finishes
integrating.
To ensure that the camera is ready to be triggered, poll the SOFTWARE_TRIGGER register 0x62C (page 91). The
concept of polling to ensure the trigger is armed is demonstrated in the AsyncTriggerEx example program distributed
with the FlyCapture SDK.
Once the trigger is reporting that it is armed, there should be no delay between when the user can enable
isochronous transmission and when they can trigger the camera. In fact, it is possible to trigger the camera before iso
is enabled and receive the image that was triggered, provided iso is enabled at some point during exposure. For
example, assuming a 10 ms shutter time, it is possible to trigger the camera, enable iso 5 ms after, and still receive the
triggered image.
Externally Trigger the Camera
At this point, one of the camera’s GPIO pins should be configured as the external trigger source, the camera should be
in Trigger Mode 0, and the trigger is armed and ready to be fired. To acquire an image, connect the external 5V or
3.3V TTL synchronization signal to the GPIO pin. Once the trigger signal is received, an image will be grabbed.
6.4.8 Example: Asynchronous Hardware Triggering (Using the FlyCapture API)
The following FlyCapture 2.x code sample uses the C++ interface to do the following:
n Sets the trigger mode to Trigger Mode 0.
n Configures GPIO0 as the trigger input source.
n Enables triggered acquisition.
n Specifies the trigger signal polarity as an active high (rising edge) signal.
Assuming a Camera object cam:
TriggerMode mTrigger;
mTrigger.mode = 0;
mTrigger.source = 0;
mTrigger.parameter = 0;
mTrigger.onOff = true;
mTrigger.polarity = 1;
cam.SetTriggerMode(&mTrigger);
6.4.9 Asynchronous Software Triggering
Shutter integration can be initiated by a register write (software trigger) via SOFTWARE_TRIGGER register 0x62C (page
91).
The time from a software trigger initiation to the start of shutter is shown below:
Revised 9/27/2012
Copyright ©2011-2012 Point Grey Research Inc.
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