Point Grey Flea3 USB 3.0 Technical Reference 3 General Camera Operation
Register Name Offset
GPIO_STRPAT_MASK_PIN_x 1118h, 1128h, 1138h, 1148h
FRAME_INFO 12F8h
IMAGE_POSITION 008h
IMAGE_SIZE 00Ch
COLOR_CODING_ID 010h
UDP_PORT 1F1Ch
DESTINATION_IP 1F34h
3.4 On-Camera Frame Buffer
The camera has 32 MB of memory that can be used for temporary image storage. This may be useful in cases such as:
n Retransmission of an image is required due to data loss or corruption.
n Multiple camera systems where there is insufficient bandwidth to capture images in the desired configuration.
All images pass through the frame buffer mechanism. This introduces relatively little delay in the system because the
camera does not wait for a full image to arrive in the buffer before starting transmission but rather lags only a few
lines behind.
The user can cause images to accumulate by enabling the frame buffer. This effectively disables the transmission of
images in favor of accumulating them in the frame buffer. The user is then required to use the remaining elements of
the interface to cause the transmission of the images.
The buffer system is circular in nature, storing only the last 32 MB worth of image data. The number of images that
this accommodates depends on the currently configured image size.
The standard user interaction involves the following steps:
1. Configure the imaging mode.
This first step involves configuring the format, mode and frame rate for acquiring images. This can be done by
either directly manipulating the registers or using the higher level functionality associated with the software
library being used. Depending on the software package, this may involve going so far as to configure the
camera, perform bandwidth negotiation and grab an image. In cases where bandwidth is restricted, the user
will want to disable transmission and free the bandwidth after the camera is configured.
2. Enable frame buffer accumulation
The second step involves enabling the frame buffer. Enabling this results in images being accumulated in the
frame buffer rather than immediately being transmitted.
3. Negotiate bandwidth with the camera
Having accumulated some number of images on the camera, bandwidth will have to be renegotiated if it has
not been done already. In most cases, this will involve effectively starting the camera in the imaging mode
configured in step (1).
4. Disable isochronous transmission and enable buffered image transfer
To transfer buffered images, isochronous data transmission must be disabled, and transfer data enabled.
5. Transmit images off of the camera
The final step involves setting One Shot/Multi-shot in order to cause the camera to transmit one or more
images from the frame buffer over the data interface.
Revised 9/27/2012
Copyright ©2011-2012 Point Grey Research Inc.
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