Components hunting

A project log for DIY CPLD board

These are my first steps into the world of CPLDs/FPGAs!

hackhead79hackhead79 04/02/2014 at 20:090 Comments

So yesternight I went component hunting for my two beginning projects (this CPLD board and the parallel port JTAG programmer necessary to program the CPLD). 

At first I searched at or rather HBE sells the complete range of products Farnell does at a very slight markup but they also ship to individuals in contrast to Farnell.

For component search the main Farnell site is a real trove though: they have free datasheets to just about any product they have on sale (I did not come across one they had no sheet for), their search is much more detailed and they list more product specifics per listing. So all in all a very good start.

I had some difficulties finding some of the parts though (in particular the 2x7 JTAG header, 9 pin 8 resistor network, etc.) so after a cursory search on I switched to In Germany (where I live and come from), is pretty cherished among DIY electronics enthusiasts because it offers a very large range of products at a very decent price point.

One or two hours later, I had all the products in my shopping cart with one exception: the tutorial board uses a PLCC socket for the main chip (as in the first example picture below - the socket is the brown thing around the chip) but Reichelt only had the VQFP-44pin version. They seem to be stocked on pretty much everything (including the 2x7 JTAG header and the resistor network) but CPLDs are a bit niche it seems (more so than FPGAs).

(nevermind the image placing / sizing - it is not quite working yet - all images from Wikipedia under Creative Commons)

A socket gives you the advantage of being able to switch the chip (second pic is an example socketable chip) in case you want to program another CPLD. The VQFP-44 version I got (reading: Very small Quad Flat Package with 44 pins - example TQFP 80-pin: third pic above) has to be soldered onto the board.

That means:

a) should I fry the chip when soldering it or by a wiring mistake or similar I'll have to (re)solder a new one - bummer! Only good thing: they cost 1.80 € a pop (about 2.50 US$) so I ordered three of them ;). I don't think I will send them all to chip nirvana if any, so I'll have one or two spare ones for other pet projects.


b) I'll have to learn how to change the PCB schematic provided by the tutorial. I'll have to switch the PLCC socket diagram for a 44-pin TQFP SMD part diagram and wire it correctly in KiCad.


c) I'll have to learn to solder small pitch SMD parts which is not one of the easiest things to do.

Sounds challenging to me but (hopefully) offers some worthwhile learning.

All in all I spent about 13-17$ per board plus components (CPLD board and JTAG programmer board) plus a parallel port PCI-Express card needed for the programmer (at about 15-20$) - so all in all not that very expensive for a start :).