WEN Signal, Data line Options, Debounce

Digital Frame Grabber Information

The WEN Signal

This single is an input to the frame grabber from the camera and is typically treated as a FTV (Field Data Valid). This signal is available on I/O line 1. The signal can be set to trigger a grab using the SetTriggerSource function.

Data line Options

8 bit, 10 bit, 12 bit, 14 bit, 16 bit , 32 bit – Bits/Pixel

For a monochrome camera this describes the maximum number of resolvable gray levels that the camera can provide. Eight bits per pixel (256 gray levels) is quite common with 10, 12 and 14 bits/pixel available in some models. A distinct advantage of digital camera results from having the digital-to-analog converter moved from the frame grabber card into the camera. This reduces the effects of transmission line noise on the quality of the image, making the least significant bits in each pixel more meaningful.

Modes – 8x1, 8x2 – Channel

As the resolution of the image sensor and the bits/pixel and the frame rate increase, larger and larger amounts of image data must be transferred to the frame grabber. To keep frame rates high many digital cameras deliver image data via multiple (synchronized) digital outputs called channels. Each channel is used to transfer only a portion of the image information. For example the Dalsa CA-D4 is 1024 x 1024, 8-bit/pixel camera can operate as either a one or two channel camera.

In order for a digital frame grabber to be able to receive more than one pixel at a time it must first have a digital input port that is wide enough to handle the number of simultaneous data bits the camera is transmitting. In two-channel mode, the Dalsa CA-D4 transmits two 8-bit pixels on each clock. A digital grabber with at least a 16-bit input port would be required.

Triggers – methods and options

A trigger signal can be set to trigger a grab using the SetTriggerSource function. The function can also define the type of trigger event that will cause the trigger LATCH_RISING, LATCH_FALLING, IO_INPUT_HIGH, IO_INPUT_LOW and DEBONCE. The input lines that can serve to trigger a grab are the Trigger line I/O line 0, WEN I/O line 1, and GPINO input 0 line I/O line number 7. (Refer to page 241 of the PXD Users Guide).

Debounce

Mechanical switches used as trigger inputs typically bounce, creating spurious edges, when the contacts open or close. You will probably need