Bob, That is what I'm thinking also but when you say the main board has nothing on it but a few connectors then why have a main board?
All the functions of the main board can be placed in a plug-in that is easy to change as technology moves. Rather then a main board you have just a cable, maybe a ribbon cable for control and status and coax for any analog signals. The problem with a backplan is that they are physically very hard to build. You need a card cadge of some kind. I think we want this to be build-able by amateurs at home. If you use a "flexible backplane" (aka, "cable") then the mechanical design is very easy, you could screw the cards down to a bread board or mount them ina 1U rack chasis, put them in a diacast Hammond box or whatever. But a ridgid backplan would dictate only one mechanical design The "soft backplane can evolve. Right now people want a "counter" and that application does not need any high speed data on the bus. Even 100Kbps is overkill. When you start taking about spectrum analyzers then you need high speed data interconnects and we can add that when the time comes. You can't do that if the bus in a PCB with connectors, you are stuck with what you have so you end up running card to card cable jumpers. May as well just start with the jumpers from the beginning. There are some really great embedded processors out. The problem is software. If you pick some "exotic" processor then you will be the only one to write software for it. To avoid that I'd pick one that "most" people already know. The bottleneck in these projects is always software and you should design hardware to minimize that problem even if it adds $20 to the cost. Moving the processor into a "plug in" module seems pointless to some people who already own a PC but if you are working with high speed data then you find interfacing that data to a desktop PC is not easy so if simply place the PC inside your project then "Poof" the interface problem is gone. The HPSDR project is a good example. They had to use a card with a FPGA on it to pre-process data to the point where it would fit down the bandwidth of a USB cable. Cost for that is a couple hundred dollars and a year of engineering but, had they simply placed the computer inside the box there would be no need for high speed box-to-PC link. Years ago this would have been expensive but today powerful CPU that can run Linux or even Windows costs very little That said the basic counter project should NOT need such a powerful CPU. A little 8-bit uP with 14 pins should be enough. On Thu, Dec 23, 2010 at 7:11 AM, Bob Bownes <[email protected]> wrote: > Just thinking out loud here, I would imagine a main board that such a > processor plugs into with locations to plug in input modules, A/D > converters, a serial level converter (if there isn't one on the board), and > a front 'control' panel. The main board holds not much more than connectors > and traces to get signals from those modules to the processor board and/or > the A/D boards. > > Hmmm. > > Bob -- ===== Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
