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[DPRG] webcam robot vision limitations
Subject: [DPRG] webcam robot vision limitations
From: Chris Jang
cjang at ix.netcom.com
Date: Wed Jun 27 11:33:56 CDT 2007
>> I think RAM may be a better medium and may be faster to read/write too.
>
>this is true, but it's also volatile so it's not suitable for all
>applications. Only dram is available in those sizes for reasonable cost,
>and it takes a lot more power than sram to maintain its data so battery
>backup is of limited usefulness.
I/O bandwidth to mass storage (SD flash card in my case) is the main limiting factor I've encountered. The PC104 computer I am using does not have DMA for the SD flash. Writes use PIO. There is device buffering in RAM which then can freeze the computer for a few seconds when flushed to SD flash. This reminds me of some digital cameras.
So a word for others who may try this - mass storage DMA bandwidth is the most critical feature to look for. CPU speed, RAM, device I/O bus speeds are not as important as fast disk or flash storage. If you see a SBC that uses SD/MMC or CF flash, make sure DMA is used.
About the storage in RAM idea - I might just try this. The computer only has 64 MB RAM. But at reduced resolution, that is enough for a minute or two of 15 fps video at a sub-VGA resolution. And so far, the electronics are very stable. I have never experienced a crash or loss of power ever in operation. So it just might work. Thanks!
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