[time-nuts] time-nuts Digest, Vol 68, Issue 99

[Bob Camp]

Hi

I can't comment on doing this with every tool out there, but I do a lot of work with Altera and Quartus. 

There are a number of people who will sell you a board with the CPLD or FPGA already mounted on it. Some are quite inexpensive, others are pretty crazy in terms of rice point. You can find simple CPLD boards in the < $30 range. For $120 you can get a very capable board with a pretty big FPGA on it. 

The USB programmer for the full line of chips Altera makes is a common item on the auction sites for $20 to $30. Often people will bundle a programmer and a board with a chip on it. The programmer and board are roughly what the equivalent parts are for most micros. The same "share a programmer" works just as well with a CPLD as with a micro. 

Unlike the situation 10 years ago, now a very full featured suite of software is a free download. The number of items excluded from the free version is very small. There is no "code limit" as you see in things like free C compilers. The software will run on Windows and Linux. 

With Quartus you can use schematic entry (.bdf file). You don't need to learn VHDL if you don't want to. You can even use TTL part models if that's what you are familiar with. I've had several guys complete CPLD projects with schematic entry and TTL equivalents. They all worked fine. You can also use the Megafunction entry tool and generate a much wider range of parts than the TTL stuff will let you do. The megafunction thing is just a click run through a set of questions thing (do you want a clear function...).  Again, it's all drop in to a schematic. 

Is this all something you can pick up and get running in under 10 minutes - no, it's a complex software package. It's at least as hard as a circuit modeling program or a board layout program. I believe that if you can run most layout software and understand digital design (what's a D flip flop ....) you can do CPLD level design quite successfully with Quartus. 

A lot of people use PIC's, but don't write their own PIC code. They grab a programmer and shoot somebody else's code. That option is equally useful with a CPLD or FPGA. The programmer software is a simple download, it's no more difficult to run than the PIC programing software. 

Is a CPLD the solution to all things - of course not. Will people who have no background in digital at all sit down and design one - likely not. If you can design a digital circuit with a dozen chips in it from scratch and then layout the board that goes with it - I think a CPLD should be a reasonable thing for that person to learn how to do. The terrific advantage it brings them is the ability to re-do the circuit without relaying out the board. No more cut traces and solder jumpers stuff. 

I'm pretty sure that Altera is not the only game in town if you want to do something like this. I've used the Altera stuff as an example only because I have a lot of experience with it. Like a PIC, the chip you pick also channels you into a free software suite from that manufacturer. It wold take more than a quick look to figure out exactly what you can do with other people. 

Long reply to a short comment ....

Bob


On Mar 22, 2010, at 5:40 AM, Dave Baxter wrote:

> Relatively easy to do in principle, and good no doubt that this would be
> results wise, it's suddenly not a DIY project any more for 99% of
> people.
> 
> Cheers.
> 
> Dave B
> G0WBX.
> 
> 
> ---- Original Message ----
> 
> Date: Thu, 18 Mar 2010 12:46:14 -0400
> From: "Bob Camp" <lists at rtty.us>
> Subject: Re: [time-nuts] Frequency divider PCB: Current status
> 	on"pre-orders", and pointers to documentation.
> 
> Hi
> 
> I think I'd just take the design over to a reasonable CPLD and be done
> it, if you are trying to improve it's floor. Having everything on a
> single "lump" of high speed silicon takes care of a lot of issues. 
> 
> Bob
> 
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