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What's Stopping You Building Your Next Project with an FPGA? (Please, Don't Blame the Cost!)

rscasny

The community does a ton of projects with MCUs. If they do the job for you, that's great. But the element14 community is about learning, experimenting and roadtesting. In this spirit, I am proposing that you should try building your next project with an FPGA (SoC), if it suits the application, of course. What's stopping you? Oh, some members have voiced the cost issue. Granted, some FPGAs do cost a lot. But chip manufacturers are rolling out economical chipsets that most makers, pro-makers or experienced hobbyists can afford. (If you can't, then apply to a RoadTest and if you win you can get a dev board for FREE.) I think FPGA / SoCs will move into a more important place for electronic designers, especially for IoT applications. Perhaps it's time to experiement with one. What's stopping you?

 

Here's a link to a current roadtest:Digilent ARTY S7 Dev Board (Xilinx Spartan 7)   Apply today!

 

Randall Scasny

RoadTest Program Manager

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  • What's stopping my design? The cost.

     

    Sure, Dev boards are getting to real good prices [I have an Arty-S7 sitting on my desk] - that's not all the cost.  There's also time costs, space costs - and prototype costs.

     

    My latest ideas tend to involve RF in some form (from satellite weather decoding to general SDR) and getting high frequency signals digitized is NOT a trivial task. Some of the PMOD connectors on the S7 are "high speed" - but how high is high?

    I have to design / make / order custom PCB's for high speed ADC's then populate them, plug them in, and THEN I get to determine if my design is flawed, or the Dev board just can't handle the speed I'm clocking in data.

    The S7 claims internal clocking over 450MHz. Can the Dev board handle a 400MHz ADC / DAC?  300MHz? 200?  150? 120?

    Can I really afford to keep making PCB's to test a design, even assuming I can get the actual chips as free (or cheap) samples? That's... daunting.

     

    Not sure what the answer is. Higher speed connectors, with specified speed ratings, would sure help. As to the format- coax? optic fibre? JESD204? The only thing I know for sure is the "Arduino" connector isn't enough when you want serious speed - and serious speed is the principle reason for changing from a microcontroller design in the first place.

  • in reply to sa-penguin

    I think you are more blocked by the cost of deployment of a high speed ADC than of the FPGA.

     

    You don't say how fast you want the ADC to sample so I can't make very specific comments but I think that you'll have all the same problems and worse trying to interface a fast (250MHz+) ADC to a micro, or to anything.

     

    The next step up of dev boards (from the Arty level) will have some high speed connectors, for example you can buy a Lattice ECP5 VERSA dev board for £250 and it has one full duplex 3.2GHz serdes channel on SMA connectors which would get you 8 bits at 400MHz, or 12 at 250MHz.

    You'll need to make a board for the ADC.

     

    MK

  • in reply to michaelkellett

    Yes, I'm blocked by the price of deploying a high speed ADC / DAC.

    I'm also blocked, in this instance, by just "not knowing" how fast I can push data through the S7.   If I knew the limit of the interface, I could select a device accordingly.

     

    As it stands, I'll have to use the 2 "high speed" PMOD connectors, along with a TI ADS4125 (12-bit, 125Msps, DDR LVDS output) and just hope for the best.

    The whole point of an FPGA, for me, is to work with DSP.

    Reducing a data stream to the point where it can be handled by a microcontroller (microBlaze, ARM cortex-M) or CPU (via USB 2 high speed connection).

  • in reply to sa-penguin

    I had a quick look and I think you may get away with the interface to the ADS4125 via two high speed PMOD connectors. You have 8 LVDS pairs on the Arty and you will need 7 of them to connect to the ADC. It will be much simpler to design the interface if you use single ended non LVDS mode although you are pushing it a little speedwise - 125 MHz is a little fast for the rather basic connectors used for PMODs but it might well work. It may well be possible to design your ADC board to work in either mode.

     

    I'll be very interested to hear how you get on.

     

    MK

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  • in reply to sa-penguin

    I had a quick look and I think you may get away with the interface to the ADS4125 via two high speed PMOD connectors. You have 8 LVDS pairs on the Arty and you will need 7 of them to connect to the ADC. It will be much simpler to design the interface if you use single ended non LVDS mode although you are pushing it a little speedwise - 125 MHz is a little fast for the rather basic connectors used for PMODs but it might well work. It may well be possible to design your ADC board to work in either mode.

     

    I'll be very interested to hear how you get on.

     

    MK

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