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Post by imlost on Oct 8, 2010 20:13:48 GMT -5
From what I found in the uclinux maillists they say, that the uC will run code from external ram damn slow and it's not worth it. So, I guess, the best bet is either to make a second board with some at91rm9200, and fpga... or stick to some opensource rtos The Cortex M3 running it's 32bit wide u-DMA controller to interface SDRAM is not supported by most development frameworks. e2e.ti.com/support/microcontrollers/stellaris_arm_cortex-m3_microcontroller/f/471/t/46439.aspxPeople use the same port for high-speed FPGA interfaces etc. Indeed, attempting to use a software emulated DMA interface will simply push the latency to high. =(
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Post by jethroevb on Oct 8, 2010 23:14:18 GMT -5
Costs.. Hm.. just running a quick check on the prices... An FPGA like XC3S500E will be about 20 bucks at most, sdram is cheap, about 3 bucks for 128mb chip (we ain't gonna route ddr in 6 layers, are we?). We might pop in an AT91RM9200 or AT91SAM, to run linux. The costs will be 50 bucks at most, I guess. Well, if you fabricate the pcb at home. More if you are off for factory made. I'm sensing that this is already a bit beyond the capabilities of a lot of people here... However, for a dirt cheap (and fun!) experiment, you could actually use the internal 1 Msps AD-converter to directly sample a black and white video signal with ultra low resolution. I quickly calculated that it should be possible to get a 52 x 41 pixel 8-bit grayscale image from a PAL surveillance camera using nothing but a wire to a header pin marked H2-1. The motor supply (12 V) could power up the camera module and there's even a microphone input in the audio codec chip. 52 x 41 pixels does not sound like much, but it would already enable all kinds of image recognition experiments. The low resolution actually kind of helps, because there's less data to handle. Each frame is about 2.1 kB so you can store several frames and do cross-correlation, for example. You could use camera modules like these: With IR LEDs: www.dealextreme.com/details.dx/sku.44677No IR LEDs: www.dealextreme.com/details.dx/sku.44679Just something to think about. FPGAs are great too, of course.
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Post by necromant on Oct 9, 2010 3:50:25 GMT -5
By the way, I looked again at this whole thing and... Well, I think I found somewhat a cool application to this thing. It can be a hell of an RC sub. I mean, just stuff it in a waterproof case, revire the motors, add LiPo instead of AA, and add one servo for up/down steering. Then just pop in a radio interface, a usb hard drive for camera recordings (Hope some rtos out there knows how to handle those, if no - let's stick to SD storage). Then we can use the uDMA to interface the rest. I doubt we can use regular webcams with any RTOS, so we are off using some analog cams, that give us PAL/NTSC signal. Then we can feed the signal to a cheap analog devices chip, that will give us digital output. Then we can stuff some mjpeg encoder from opencores.org into the FPGA and interface it with the uC via uDMA. So, the only thing the uC has to actually do: take the compressed video, and write it to storage...or send it via radio. The worst problem here is the waterproof casing. ANyone has any ideas how one can make in his home lab ?
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Post by necromant on Oct 9, 2010 3:53:17 GMT -5
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Post by Parker Reed on Oct 9, 2010 12:22:28 GMT -5
I see a lot of potential in this little guy.
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Peter
New Member
Posts: 2
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Post by Peter on Oct 9, 2010 13:26:48 GMT -5
The first thing I'm going to do is fit mine with infra-red leds and recievers seeing as i managed to get 2 (home and work email addresses and i would like to get them talking to each other. Another upgrade i would like to make is table edge sensors, probably hooked into the bump sensor inputs as i dont think i will need to differentiate between hitting something and coming to a table edge. Other than that, maybe a platform on top for placing drinks on, or even a miniature gripper/arm
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Post by jethroevb on Oct 9, 2010 22:32:41 GMT -5
Btw, have you ordered any of those? Do they really output 380TVL? Can you encode and show a couple of videos filmed by these? I haven't yet. I'm going to order the one without the IR LEDs when I know for sure that TI will send me the bot.
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