FPGA development on the cheap - was Re: [sdiy] uC with mul

[Brock Russell]

H^) harry wrote:
>I used OTP, flash is available at 10X the price.  I don't think I'll
>upgrade that often so I shoot the dice... hoping they are loaded in
>my favor. Ain't that what engineering is really about ???

Yes...engineering is all about cost. Figuring out what cost is the
tricky part. You really look like a genius when you can implement
that new feature (that marketing/management always wanted but
didn't tell you about) in the field without having to do board rework
or replace parts.

>These are serial eeproms so very little board space is needed.
>
>H^) harry   (who still laments the development costs....)

Okay Harry, the (almost) free Xilinx development system:
1 - Xilinx WebPack 
http://www.xilinx.com/xlnx/xil_prodcat_landingpage.jsp?title=ISE+WebPack
2 - Manuals http://toolbox.xilinx.com/docsan/xilinx4/pdf/manuals.pdf
3 - DIY JTAG programmer cable - you probably have the parts to build this 
http://toolbox.xilinx.com/docsan/3_1i/data/common/jtg/dppb/appb.htm and 
JTAG Programmer Guide ftp://ftp.xilinx.com/pub/documentation/cpld/jtag.pdf 
which has the schematic in it too.
4 - Parts. Well you still have to buy something unless you are on really 
good terms with your Xilinx distributor or rep. If you don't want to buy an 
eval board - even if they are a great deal and save so much time they pay 
for themselves before you kludge your first design together - then go with 
the Spartan-XL that you have already used, as it comes in an 84 pin PLCC, 
so you can use a through hole socket and perf board. Cost if you can find 
them will be about $15.

For those who want eval boards, Insight has very good ones that come with 
reference designs. http://www.insight-electronics.com

So now you have all the bits to do Xilinx FPGA and CPLD designs for under 
$30, $130 if you buy the eval board.

Next step is to actually implement a design.

The new WebPack tools support schematic capture so you don't have to learn 
an HDL, but if you are used to View Logic or any serious schematic capture 
tools, these will surely drive you crazy. Still, they work. You just need 
to check out the Libraries Guide in the manuals and work through one of the 
tutorials. The ISE 4 tutorial is probably okay.

For HDL designs I went with VHDL. Can't really comment on Verilog other 
than it looks easier.
VHDL for Programmable Logic is perhaps the best book on the subject, but it 
costs money. The Xilinx stuff is free but I didn't find it alone was 
sufficient for me to learn VHDL. I read everything I could find on the web. 
For learning how to do Xilinx VHDL designs I would read the following:

Peter Ashenden's "VHDL Cookbook" 
http://www.ecsi.org/EARNEST/digests/VHDL_cookbook/default.htm and many 
other places.

Xilinx Synthesis Technology (XST) User Guide 3.1i 
http://support.xilinx.com/support/sw_manuals/3_1i/download/xst.zip

Synthesis and Simulation Design Guide 3.1i 
http://support.xilinx.com/support/sw_manuals/3_1i/download/gensim.zip

Actel HDL Coding Style Guide http://www.actel.com/docs/R2-1999/hdlcode.pdf
This covers the same stuff as the Xilinx manuals but I think it is 
presented more clearly.

Tutorials:
I worked through the Insight Counter reference design, 
http://www.insight-electronics.com/Memec/iplanet/link1/ref_design.zip and 
the Xilinx Johnson counter tutorial that comes with the WebPack. Both had 
errors when I looked at them so you either get totally screwed up or 
realize you know what you are doing.

And then you are designing...

Brock