6502.org

There's a relatively recent tabulation of dev boards at
https://www.joelw.id.au/FPGA/CheapFPGADevelopmentBoards

and JensEP has found a couple on ebay in the $30 range with Xilinx Spartan 6 LX9 chips on board, with USB interface, LEDs and buttons (but no big RAM) - search for Xilinx Spartan 6 XC6SLX9 or similar. At time of writing there are offerings from sellers 'eepizza' and 'cantonelectronic' - see this post which also links to a couple of Altera Cyclone IV boards (EP4CE6.)

Dave's posted some selected inexpensive boards over here.

Enso has made his own board, for sale here.

Grant's MultiComp design is here.

Jason's Matchbox board is here. [As noted below, this has 32-bit wide SRAM, accessible as 16-bit wide but not on a byte boundary - unless you use only half of it or make a more sophisticated memory controller on the FPGA.]

Ed,

Although the Matchbox board has a 32-bit RAM interface, it is implemented with a pair of 16-bit SRAMs, with the same control signals (CS, OE, WE, UBS, LBS) going to each SRAM,

This unfortunately means that byte writes are not possible, making it harder to implement 32 bit processors.



I did ask Jason if it was possible to fix this in the next manufacturing run, but the board is too tightly packed to change this without pretty much starting again.

Dave

Interesting limitation, noted. (We should start a new thread if we're to embark on a discussion about more sophisticated memory interfaces.)

At the risk of being perceived as a self-promoting ***hole, I would like to mention that OberonStation does it right. All the control signals of the two SRAMS are brought to separate FPGA pins, allowing for clean 32-bit with byte access, 16-bit or 8-bit operation. It feels good to do something right, at least once in a while -- I was tempted to save a few wires at one point...

I mentioned in the DIP-format FPGA board thread that there is now an open source toolchain for Lattice FPGAs. Here are a couple of dev boards with Lattice parts:

The myStorm is an FPGA+ARM with lots of 5V-tolerant I/O and a Pi-friendly stackability, a project in progress and expected within a couple of months:
https://folknologylabs.wordpress.com/20 ... /#comments
https://hackaday.io/project/12930-mysto ... -dev-board
Will maybe be about $30

The Lattice iCEstick FPGA Evaluation Kit is a little board with USB connector and 16 DIP-ish 3V I/Os:
http://www.latticesemi.com/icestick
http://www.mouser.co.uk/new/Lattice-Sem ... stick-kit/
About $15

Very nearly ready to purchase, the ZX-Uno retro emulation platform, which looks like an FPGA/RAM/video/audio dev board with an expansion port.
Links and details at
http://stardot.org.uk/forums/viewtopic. ... 00#p144000 (The expansion port has a rather unusual layout, and is almost certainly not 5V tolerant. The RAM is byte width. The VGA signals are on a non-standard pinout.)

Rob mentioned the CMOD A7 in another thread - it's a 48-pin breadboardable module, with a choice of two rather new Xilinx FPGAs - up from our usual Spartan 6 to the Artix 7 generation and with 10k or 20k 6-input LUTs. It's programmable over USB, and has 512kByte of 8nS SRAM (fast, but only 8 bits wide) - the FPGA also has up to 200kByte (Xilinx pdf) of on-chip RAM.



It can be powered by USB or by the pins, with 3V3 or 5V supply (PDF datasheet), but as is now normal the I/Os are not 5V tolerant.

Seems to be $75 or so.

(One thing about the newer FPGAs from Xilinx is that you can no longer use the ISE software, you have to use the Vivado software - both available at no cost but I'm not sure how usable and reliable Vivado is, especially from the command line.)

I don't have experience with ISE, but I do have experience with the Quartus tools for Altera (now Intel) FPGA's, and I think I like Vivado better than Quartus. I think Vivado has a more intuitive user interface, does a good job of suggesting next steps when you're in the middle of a design, and works a bit faster than Quartus too (compiling the same SystemVerilog design).

Vivado does have a command line interface (a Tcl interpreter; I think Quartus has one too) and it can import ISE projects no problem, as far as I can tell.

(All the above was based on a few evenings of tinkering with the Digilent Arty with the P1V (Virtual Propeller) design by Parallax. https://github.com/JacGoudsmit/P1V).

===Jac

Thanks! I remember when ISE was deprecated and Vivado arrived there was much distress. Hopefully it's much better now than when introduced.

That $99 Arty board is another one to think about:

and it comes with a voucher for Vivado (a better edition? Not sure)

(I did previously buy a board with a ChipScope voucher - haven't used the resulting licence but at least I have it.)

That Arty board looks quite capable for a reasonable price.

It certainly does! The DDR3L seems a bit intimidating to me, but perhaps not to you! (The reference implies you can use a supplied interface module to get to an AXI4 (AMBA) interface, so perhaps that's fine.)

The DDR3 would be very intimidating if I had to interface it myself, but having working hardware and a Xilinx wizard to do the critical bits inside the FPGA makes it a lot easier.