Arduino-Compatible FPGA Shield

​As the project unfolds, I've planned to produce some content - could be a video, could be a doc - that details the process I'm going thru.  The first video in that series is posted now on YouTube and available for viewing at:  

This video really gives the top level and explains the basics of what an FPGA is, what the various components are that we're using and why, and how this is intended to interface to the Arduino.  Also some details on where all of my project resources are stored and how to get at them.

Accessible here with markup:  http://www.datasheet.net/document/566207/

​Realizing I've got heaps of room on this board, I've gone ahead and tweaked my choice of Flash memory.  In this case, I'm still doing SPI programming of the FPGA, though using a Spansion part (at least for prototypes...I'll try and cost this down for production).  The device I've chosen is S25FL216K0PMFI041.  Digikey showed the part at $0.39 however findchips shows Verical selling these for $0.31.  See:  http://www.findchips.com/search/s25fl216k0pmfi041

​For those interested, I setup a working directory on git for this project (https://github.com/sfgit/FPGA_Arduino_Shield).  I've uploaded a few libraries today also for the FPs and a !very! generic PCB (just the imported board shape and some parts to get the area-costing down.  Now that I know what sort of space I have to deal with, I'll go back and start cranking on schematics and getting the schematics together.  

The board in the repo is for reference at this point.  I will be hacking this apart and redoing all of this as layout takes flight.  This was just an easy import from Eagle to my tool of choice (Altium) to get board dimensions and such.  

​Did a preliminary BOM today and selected a few key components, incl. the Spartan 6 variant I'd like to use and the SDRAM and Flash devices (may go with a BGA SP6 package with more IO...no risk yet to the design, regardless of what I choose).  All looks good for ~$25 component cost + PCB (not including Assembly).  Small quantities should still be under $30 assembled and allow me some wiggle room to add other cool things like perhaps a temp sensor or current sensor, what-not.  Alt. is to do a total breakout board as a second shield that gives heaps of IO.  Depends on FPGA choice.  

Also did a preliminary layout (verifying board size and available space).  Even with the QFP FPGA, that is 20x20, the SRAM is 8x8 and the Flash is 6x5.  Awesomely small.  Very cool.  

Next step, power rails and decoupling schema.  Easy enough.  Then build parts and create a schematic.  Stay tuned.