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linking two fpga boards

I have a ready built design with a cyclone device offering nothing more than some (around 5 maybe) unconnected io pins showing up on a standard connector (pinhead, IDE-like) and like to transport out data as quickly as possible into another board for test purposes. I am thinking of just adding an eval board an linking them via a logical upload channel.

The question is, how this could be done easily? I intend to use a kind of serial connection and wire it directly - could a differential pair be of some use here ? What data bit rates colud I expect?

Different ideas ?

Thanks

Reply to
alterauser
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You are not giving enough information. How far the boards are? Do they share a common ground? Does the second board have the same FPGA? Can you put a UART into each of the FPGAs? How quickly is quickly enough? In other words how much data in how much time?

/Mikhail

Reply to
MM

Ok, you might be right, so some more info:

The first board is industrial und unchangeable. I only can add some VHDL to the exisiting design and do a resynthesis. There is enough room in the fpga to add a uart or anything I like. The second board does not really exist, but I have no time to built something special. so an eval board will/must do.

The boards of course yet sharing nothing, neither ground nor VDD. But of course I can add gnds for example. The first board contains a xilinx spartan, the second possibly too . I am free in this.

Well, of course I had the idea to take a big fpga and warp the existing fpga design to put into the new board for evaluation - but this gives me only limited information. I have also to use the surounding hardware of the industrial board.

Does it suit, to only use a simple IO-Line, GND and a clock to come out with 100MHz ? Can I use a kind of twisted pair? Or better someting shaped as an IDE-cable?

I am currently not yet familiar with these "differntial pairs" - I only know about using symmetrical wiring from analog domain. Is this similar ?

Reply to
alterauser

alterauser schrieb:

look at Ken Chapmans ultra compact UART macros a very simple solution would be using LVDS half-duplex UART you only need 2 wires and can transmit maybe at above 100MHz bit rates

Antti

Reply to
Antti

The OP would need to be careful about the very low common-mode voltage capability of LVDS in an 'industrial' setting. IME you need a decent ground connection between TX and RX with LVDS, and will then need to arrange things so that the ground doesn't inadverantly start to carry its share of the hundreds of amps which are often flying around the place.

But I suspect that if a 100MHz inter-board connect is really needed, someone more experienced is going to be needed to help with it...

Will

Reply to
Will Dean

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