[sdiy] FPGAs

[Eric Brombaugh]

On Jan 28, 2011, at 4:15 AM, Matthew Smith wrote:

> Quoth Jason Tribbeck at 28/01/11 21:37...
> ...
>> It's not too bad - I did a 208-pin Spartan-3E just before Christmas. It was the first time I'd done a chip with that many pins (previous "record" was 160 pins) - I did get one edge slightly off-centre, and it was a bit of a pain straightening it out. I just wasn't paying enough attention (three sides were fine; it was just the fourth).
> 
> Maybe the solution to *that* part of the problem is to throw together a generic development board - with a breakout board with an regulators/clocks on-board - send my Eagle files off to Futurlec and get them to fab it with solder mask. The solder mask might help with assembly.
> 
> As regards the programmer - since it looks like everyone's got a free tool I can use which accepts both Verilog and VHDL, availability of a cheap (as in $50 cheap) programmer or something that's easy to build, this might be the deciding factor for me.

I've done a number of Xilinx-based boards targeted at audio / synth applications which use hand-solderable devices and don't require programmers. Instead they store the FPGA bitstream on SD cards which are read at boot-time. See here for more details:

http://members.cox.net/ebrombaugh1/synth/armfpga/index.html

http://members.cox.net/ebrombaugh1/synth/dsPIC_fpga/index.html

Manufactured with 2-layer boards that should be compatible with inexpensive PCB fab processes. The design files and driver firmware are available for both.

There are also pre-made FPGA development boards that are quite inexpensive ($90 range), don't require separate programmers and which have sufficient I/O to do audio, such as this one:

http://www.em.avnet.com/evk/home/0,1719,RID%253D%2526CID%253D62855%2526CAT%253D0%2526CCD%253DUSA%2526SID%253D32214%2526DID%253DDF2%2526LID%253D32232%2526PVW%253D%2526PNT%253D%2526BID%253DDF2%2526CTP%253DEVK,00.html

Note that Avnet used to sell a cheaper Spartan 3A board but I can't seem to find it any longer.

Digilent is now manufacturing an I2S audio DAC PMOD that's compatible with many inexpensive dev boards and is good for audio:

http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,401,858&Prod=PMOD-I2S

They also have a number of inexpensive development boards (as well as some very expensive ones too) that are worth looking at:

http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,400&Cat=10

Eric