Problem with acquisition window setting on PCIe 1429 frame grabber

[xiaochunfly]

Hi all,

Recently, I am trying to use Basler camera A504k together with PCIe 1429 frame grabber for high speed image acquisition. I found problems with acquisition window setting in the frame grabber using software Measurement & Automation Explorer.

1. For example, if the original image size is 1280*500, if I set the acquisition window with left 0 and width 1280, everything is OK, but if I set the width to 1279, there would be a error (Error 0xBFF6002C FIFO overflow caused acquisition to halt), if I set the width to multiple of 8, there would be any error. Could someone tell me why this happens, is that because the data package transfer rule for the frame grabber?

2. The acquisition window is set according to the image from the camera, right? If the camera also have a function of Area of Interest, the acquisition window setting is still corresponding to the image obtained from the camera.

Attachment is my setting one the MAX software.

Thanks a lot

[BlueCheese · Accepted solution]

Hi xiaochunfly,

My bet would be that the 1280-pixel image size is 32-byte aligned and the hardware can effectively go from line-to-line without breaking up the transfers. With the non-aligned width it needs to start a new transfer on every line and this has some extra overhead on the PCIe bus and system memory bus. Currently the IMAQ infrastructure tries to accommodate any possible image size/border size regardless of the efficiency it will have to the hardware and changes in recent Intel-based chipsets have reduced how effectively the system memory bus performs under these conditions. Thus, you can achieve much better performance if you use aligned widths. You might also want to get the latest IMAQ driver because there have been changes in the past few releases to make the transfer more efficient under some of these conditions.

Usually the AOI corresponds to the framegrabber's point of view. If you reduce the AOI that the camera is sending, it often looks identical to the framegrabber as if you just had a camera with a smaller sensor. Thus, your AOI in IMAQ should be set to the size the camera is sending, unless for some reason you want to capture less than what the camera is able to configure on its own.

Eric

[xiaochunfly]

Hi Eric,

Thanks a lot for your explanation, I think that might be the reason that the smallest transfer package is fixed to 32Bytes, thus if the overall pixel numbers are not multiple of 8, then the FIFO memory for  writing operation would have overflow problem.

Shihao