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zygot

Useful EVMs for FPGA Developemnt Boards

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It's not easy adding Analog to your Digital for non-audio applications on a typical FPGA development board. I thought that some of you might find my experiences with the following useful. All of the following can be found from a distributor like Mouser or Digi-Key.

You have to be careful because, especially for high speed ADC/DAC EVMs a lot of boards have HSMC and FMC type connectors that aren't compatible with the standard interfaces. Sometime you can cobble up a work-around but usually not. Before spending any money on an EVM you need to do this**:

  • Read the data sheet for the featured device very very carefully to make sure that it can do what you want it to do. This is not nearly as simple as you would think, especially  for ADC devices  where specmanship, little white ( sometimes closer to black ) lies, and covering up 'features' that might render the device useless for your requirements has always been the rules of the road.
  • Pore over the schematic for the EMV and trace every pin through the connector to ensure compatibility with your FPGA board. Pay particular attention to power supply pins.
  • Download the supporting software, when available, and understand what you get or don't.
  • Understand that good ADC interfaces, on the analog side, tend to be very application specific. The ADC demo boards tend to be general purpose; but not always. Not listed below is the ADS4449 EVM  that I managed to get working with the KC705 board a number of years ago. This 4 channel high speed ADC EVM is set up for narrowband processing of signals centered around 185 MHz. It served it's purpose but I can't recommend it.

         
HSMC compatible boards.

ADC/DAC

Linear Technology DC2459A LTC1668 16-bit 50 Msps DAC 

This is one of those rare EVMs designed to connect to an FPGA development board. It can connect directly to a board with an HSMC connector, a DE0 Nano, a Mimas or Mojo board.  Mine is always attached to a DE0 Nano and ready to go. I use an external TTL USB UART for control. The DE0 Nano is a cheap and very handy board to have around. ( If only it had a nice Artix FPGA... not that I have anything against the Cyclone V )
 
Linear Technology DC2390A for LTC2500-32. 2 LTC2500-32 32-bit ADCs and 2 LTC1668 16-bit 50 Msps DACs

Connects to any FPGA  board with an HSMC connector. The EVM is intended to be used with the Cyclone V SoCkit and has slick software support if used with this ARM based board. I prefer rolling my own interface and using another FPGA platform. Interesting approach o the software side.
 
Terasic makes a couple of not too expensive ADC/DAC HSMC compatible add-on boards. I've already posted a description of a demo project that I completed ( well as far as I need to for now ) recently showing one way to use the Ethernet PHY to make use of such boards. In recent years I've really lost my enthusiasm for low end Intel FPGAs and Quartus tools so that post isn't as silly as you might assume that it is.

USB 3.0

Both FTDI and Cypress offer reasonably priced development kit options for using their USB 3.0 interface devices for both HSMC and FMC connector equipped boards. In fact for the FMC versions these are among the only inexpensive mezzanine boards that you will find. I much prefer the flexibility of the Cypress FX3 but be aware that you need to do some embedded ARM development and there's a steep learning curve. If you want to learn about USB this is the way to go.

FMC compatible boards.

The FMC ecosystem is, with few exceptions, a very expensive place to play in. However on rare occasions you can get lucky. Understand that none of the boards below were intended to connect directly to an FPGA development board.

Analog Devices EVAL-AD7761FMCZ AD771 8-channel 16-bit Simultaneous Sampling ADC.

I've used this board with the Nexys Video with minimum effort. This is one of those devices where you can be very disappointed if you don't completely understand everything in the data sheet.

Analog Devices EVAL-AD7616SDZ AD7616 16-Channel DAS Dual Simultaneous Sampling ADC.

This board requires a SDP-I-FMC interposer. I didn't complete a project using it but haven't run into any obstacles hardware-wise. This is another device that requires very careful scrutiny before deciding that you want to spend your time or money on it.

** This advice also applies to FPGA boards that you are thinking of purchasing.

  • If you want to use a particular feature, say DDR, find out if the vendor offers a usable demo showing how you might use  it for your project. Find out if you need an evaluation license to build the demo for yourself in order to use that feature. There's only one way to do this...
  1.  Before making a purchase install Vivado or ISE and see if  you can actually build the demo projects for a board.
  2.  Support, support, support. So what kind of support is provided for the board that you are interested in? Digilent is all over the place here. A very few boards have demo projects with HDL sources. One such board is the Nexys 7-A100T (Nexys 4 DDR) that has an OOB with VHDL sources for most of it's features. It does have a few IP .xco files that are supposed to work with Vivado 2018.2. I was unable to use the sources to generate a bitstream using Vivado 2018.2 SP1. ( I don't have the board so I didn't spend a lot of time trying only because I wanted to look at the DDR IP to reply to a posted question regarding DDR performance.
  3. Companies can pretend to offer more support than they really do by offering board design Xilinx IP flow demos. I personally, want to see HDL source as a measure of commitment to a  product. Even though Digilent has shown that it's possible; it's hard to mess up an HDL demo.
  4. If there's very little in the way of providing build-able demo projects for board features or it take years to provide  a reasonably accurate User's Manual these are big red flags. It doesn't mean that the board is useless, just that you had  better have the experience and skill, and most importantly for me the time to write your own interfaces

    
    
Tips for beginners.

  • Not everything that board or even IC vendor makes is wonderful. If they spent money developing a product then they sure will try to find a customer to pay for those    development costs. Sometimes, the only way to identify the dirty little secrets is to observe what's missing in a data sheet or sales blurb. If a normal feature is usually    highlighted for most similar products and noticeably absent for the one that you are eyeing then this is a big red flag. What's missing is sometimes more informative than what's stated.
Edited by zygot

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