Electronics > FPGA

Cheap 250Mbs Link between Boads

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ali_asadzadeh:
Hi,
I want to design a new project for the customer, I want to send Data between boards with the least amount of wires, there are around 200 boards and they should send their data to the next Board, and the data rate is around 250Mbs, also the boards are around 50-60cm away from each other,
I was thinking of using RS485, But the data Rate is limited to 50Mb, so I was searching other options, Ethernet is out of question because of the cost, So I thought maybe Select IO from spartan 6 parts Like the LX9 part can come handy, is there a way to make a UART liked interface @250Mbs, what about the Physical layer? should I go with LVDS? any Ideas or hints would help a lot.

laugensalm:
You might want to forget any asynchronous solution and use a 10b8b coding on the physical layer, as DVI does. If you're not stuck with Xilinx, you might want to look at the gear boxes in the mach XO[2-3] FPGAs, there are also neat ref designs that work over a Ethernet cable (without the Ethernet protocol). I've also abused DVI-alike protocols over SATA cables and HDMI (off standard) for such hacks with no issues. And not to forget some real time issues with deviating clocks on sender/receiver, but I assume you've thought about that already.

glenenglish:
2 x DDR LVDS pairs
125 MHz clock and  data.  will easily make it between two boards on twisted pair. Use two pairs out of an RJ45.....

any fpga would do that.

why would you even consider an Spartan6 , unsupported tools ?? , unsupported silicon ???
You are designing a product for a customer ! not a doorbell for your house...
There is plenty of QFP  FPGA around.... Trion T20  .... , Lattice XO2,

BrianHG:
Even every single slowest worst lowest power Altera FPGAs can achieve those bit-rates on every pair of IO pins.

glenenglish:
And you'll need to use shielded Cat6 cable to meet EMI. (and EMC), with shields connected each end.
Like, you will be very unpopular (and in alot of trouble) if your clock/data radiates enough to cause trouble in the aviation band, or public service radio bands

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