cmucam3-hardware (#1) - Higher res camera? (#12) - Message List
I would like to attach a nicer camera sensor to the board, something with a bit higher resolution, and I am interested in any suggestions.
Initially I thought it would be possible to hook up an OV part that supports VGA (640x480), since the FIFO is listed in the CMUCam3 spec is an AL4V8M440, which appears to be eight megabits (1MB).
However, the boards that I received from Seattle Robotics contain a 4 megabit FIFO chip.
Any thoughts?
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Message #25
I have tried using the ov7660 with mixed results on a similar board to the cmucam3. It can produce a 640x480 image. I was able to get images from the camera, but without knowing just the right register values it is hard to get it performing well. In the end, the images ended up having very poor color depth and looked quite bad. Even with the 6620, lots of guess work went into find some good stable register combinations. Omnivision has never been much help over email and has poor documentation. In fact, problems with omnivisions sensors stopped us from using the ov6630 which is supposed to be a drop in replacement for the ov6620. The 6630 had some issues with the image highlights being saturated and rolling over to bad values. I think these problems are due to omnivision only caring about large companies making millions of cellphones.
Seattle Robotics is using the AL440 instead of the AL4V8M440 because of problems with the AL4V8M440 chips. They seemed to die frequently on us during testing and many times they would glitch when capturing images. As it turns out Averlogic stopped selling them for a while which was likely because they also saw problems with them. Its too bad, because our hope was to support the high resolution mode on the ov7620 camera. The AL4V8M440 is pin compatible and will work on your board without any software changes. The trick is getting some that don't have defects.
I don't mean to dissuade you from trying other sensors. I think it would be great to try using some of the new Kodak sensor. They have very good datasheets and Kodak seems to respond well to email questions. You could even try carefully swapping out your FIFO with an AL4V8M440. Even with the current FIFO, a newer sensors might give cleaner images, less dark noise and better dynamic range.
-Anthony
agr05/15/07 17:28:17 -
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Message #26
Anthony, thanks for the detailed information and the quick reply, this is very useful.
I haven't been able to find any other project/development boards that either include a camera sensor, or a fat enough buffer configured in a way that a camera sensor could be attached.
Do you know of any alternatives to the CMU boards?
Thanks,
DS
dscott05/15/07 18:41:31 -
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Message #27
One alternative that I have used is a blackfin DSP based vision system made by bluetechnix. You can find more information on their website: http://www.tinyboards.com/rainbow2006/site/tinyboards/__extender_boards/__ext-bf5xx-camera/324/ext-bf5xx-camera.aspx
Unfortunately, they are very pricey (at least $650 USD not including a jtag debugger) and they don't have very good open source support. I'm sure with the analog devices compiler it works well, but that is even more expensive. You can run ucLinux on the blackfin which works quite well. The bad part is there isn't a ucLinux camera driver that works with the camera that comes with the system. I have been writing my own driver and am having the usual strange omnivision problems. GCC isn't that good for the blackfin right now either, so you might need to do some hand assembly to get good performance.
The good news is that if everything works, the blackfin is a slick processor. With the DMA frame grabber (PPI), loading high resolution images into a large memory space is very quick.
-Anthony
agr05/15/07 23:34:12
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