Xilinx Spartan-7 FPGA Maker Board by Digilent giveaway

That's a really generous offer. It's things like this that really makes this feel like a community.

I was thinking of trying out FPGAs but after some deliberation (and advice) I was thinking I was more likely to go the Cypress PSoC route. I'm sure someone else will jump at your very kind offer.

I've spent some time this morning looking at the PSOC programmable logic in the light of several comments in E14 suggesting it as a low cost route into learning about FPGA.

My conclusion is that it is no such thing.

The programmable logic in the PSOCS is minimal, each UDP amounts to a rather limited pair of PLDs and a kind of odd ultra risc 8 bit processor (DataPath module). The biggest PSOCs have 24 of them. As a peripheral to an ARM Cortex processor it's quite nice and might be useful for quite a range of things - but using it is nothing like using an FPGA. The best bit of it (the Datapath module) is programmed in the Cypress tools (doesn't appear reasonable to program it in Verilog). To try and put it into perspective - the CPLD logic in the biggest PSOC is about 192 LUT + flip flops and the datapaths about another 768 pairs - just about equivalent to the very smallest (1000 LUT Lattice ice40 FPGA but only 20% or so can be programmed sort of like an FPGA.

So if you want do something specific and the PSOC fits the bill - great.

If you want to learn about FPGA and FPGA design flows - get an FPGA. It might cost you £20 more, but no worse than that, you'll be able to choose between VHDL and Verilog (or use both) and what you learn will be much more generally applicable.

MK

michaelkellett You definitely have some good points and extensive FPGA knowledge. Your input is much appreciated. However, everyone's requirements are different. If the PSoC turn out to not be quite what I thought (or I get the bug and want a "real" FPGA), then the iCEstick is on my list.

Anyway, let's not clog up kk99's generous offer thread with slightly off-topic chat.

Wouldn't the ALU add greater flexibility and compensate in some way the low count of lut?

One of the good features of E14 is the amount of off topic chat

MK

I did a lot of research into the PSoC 5 when it first came out.  I was excited to see that almost all of configuration registers were documented, so that it would be possible to write my own design tools.  I was then disappointed to find out that the routing registers were not documented, so you're pretty much limited to using PSoC Creator which requires using a Windows machine.  Ah well.

I did see that PSoC 5 (and 4) are really quite marvellous chips, but I agree with Michael that they're really not FPGAs.  A PSoC 5 is like having a big breadboard with a bunch of PLAs, a bunch of bit-slice ALUs (actually byte-slice), analog components, and a reasonably powerful CPU well-integrated with the other devices, all smashed into a tiny chip.  It's a nifty device for playing with lots of different technologies provided that you're willing to tolerate Windows.

The PLAs are reasonably powerful, but 48 PLAs is not the same as a proper FPGA with thousands of logic elements.  PLAs make dandy "glue logic", but you'll soon run out if doing a serious logic function.

I still recommend iCE40 as a great starting FPGA and also as a solution when you need a relatively small FPGA.  You can get 1K gate parts in QFN, VQFP and TQFP packages.

To David Murphy: I suggest downloading both the iCE40 data sheet and the PSoC 5LP architectural reference manual.  Read each one for one hour and see how far you get

I did a lot of research into the PSoC 5 when it first came out.  I was excited to see that almost all of configuration registers were documented, so that it would be possible to write my own design tools.  I was then disappointed to find out that the routing registers were not documented, so you're pretty much limited to using PSoC Creator which requires using a Windows machine.  Ah well.

I did see that PSoC 5 (and 4) are really quite marvellous chips, but I agree with Michael that they're really not FPGAs.  A PSoC 5 is like having a big breadboard with a bunch of PLAs, a bunch of bit-slice ALUs (actually byte-slice), analog components, and a reasonably powerful CPU well-integrated with the other devices, all smashed into a tiny chip.  It's a nifty device for playing with lots of different technologies provided that you're willing to tolerate Windows.

The PLAs are reasonably powerful, but 48 PLAs is not the same as a proper FPGA with thousands of logic elements.  PLAs make dandy "glue logic", but you'll soon run out if doing a serious logic function.

I still recommend iCE40 as a great starting FPGA and also as a solution when you need a relatively small FPGA.  You can get 1K gate parts in QFN, VQFP and TQFP packages.

To David Murphy: I suggest downloading both the iCE40 data sheet and the PSoC 5LP architectural reference manual.  Read each one for one hour and see how far you get