Problems with xBee

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Postby JonSenior » Mon Oct 01, 2007 9:07 pm

Rudeofus wrote:
brittonphotography wrote:But we don't need a CPU/MCU in our receiving circuit. An FPGA can do the same (albeit with more effort) without replicating micro controller behavior.

Ouch! FPGAs are cool, but that's going to do nasty things to both the work load and the wiring. I'm currently trying to find out how the Elinchrom units get around this. Given the remote control of flash intensity that they offer, it seems strange that they wouldn't be using a micro. Personally, I'm not convinced that adding a micro to a radio remote trigger counts as an inventive step, but the US patent office think otherwise and sadly unless I can find prior art in the either the European or US databases the only way to test this would be in an expensive court case.

Apart from FPGA, we could try to use some special purpose processors like signal processors (the AD2181 doesn't even have a push/pop instruction, how much more special purpose can it get?), some are even supported by the GNU toolchain.

I think I'd rather code for FPGA. :(

PS: Since the pocketwizard patent so specifically mentions that their invention employs a CPU, I assume there was prior art for triggering a flash via a simple RF link.

I think actually remote triggering via any method is covered from a while back (Polaroid seemed to have something from the mid 60s that covered remote flash triggering). As I mentioned, I find it dubious that the micro counts as an inventive step. The problem with patents in this day and age is that the examiners often have absolutely no idea what they're talking about. (I know the lawyers don't!) which makes it easier to patent a "non-inventive" invention.

I'll keep hunting.

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Postby MQ » Tue Oct 02, 2007 5:29 pm

JonSenior wrote:I think actually remote triggering via any method is covered from
a while back (Polaroid seemed to have something from the mid
60s that covered remote flash triggering).

I have a Polaroid remote for the SX-70 that used RF.
The receiver uses a relais to trigger the camera.

Nothing big, and 30 cm wire antenna suggest it's nothing big.
As long as the transmitter is depressed, the relais is active/short.
If you are not part of the solution,
you are part of the problem.
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Re: We can't use XBee :-(

Postby seaton » Thu Oct 04, 2007 8:24 am

Rudeofus wrote:It appears that pocket wizard has a patent on radio links attached to photographic equipment where micro processors are used on both end of the link. This pretty much kills all suggestions of smart RF modules, since all of them have CPUs inside in order to be smart :-(

So either we find really dumb :-P receiver modules without CPU circuitry inside, or we have to hack up something ourselves ...

What country do the patents apply to? US, worldwide? If the patent is not worldwide then I see no problems. Our best bet is to come up with a design etc that people can go and get off the shelf components and build it them themselves.

If we were to go down the FPGA route, how easy is it for the end user to customise the units? i.e. download personalities, write their own etc? I would say very hard (but I have no FPGA experience).

I have yet to read the patent but from my initial glace it does seem very generalised, but will be my homework for tonight :)

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Postby strogg » Thu Oct 04, 2007 1:28 pm

I'm doing work with Xilinx FPGAs right now. I only started about 2 months ago, and I'm confident that I could come up with some kind of control circuit. There is a significant learning curve.. one bigger than using an MCU like the atmega, but it's not insurmountable.

We wouldn't actually want to use an FPGA, as they have volatile memory, and we'd need to include some kind of flash on the board as well. Instead, we could use a CPLD, such as the coolrunner, from Xilinx. They're very similar to the Xilinx FPGAs but they are much smaller, much cheaper and have non-volatile memory.

The cheapest FPGA in my (year out of date catalog) is the Spartan XL.. it's a 100pin package with 77 IO pins and 5k gates for 10.69. (8.52 if we buy 100). The cheapest CPLD is the Coolrunner II, which is a 32pin package, 21 IO pins and 750 gates, for 1.68$ (1.50$ if we buy 100).
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