[sdiy] Tiny boards anyone ?

[Eric Brombaugh]

jbv wrote:

> Mmmh... please correct me if I'm wrong, but AFAIK VisualDSP+ can be
> downloaded and used for free as long as it's hooked to an ADI kit (with
> certain limitations in code length, but that seems more than enough for
> a hobbyist)...

I haven't found that caveat. I did see that the full version costs 
$3500.00, and that they have a 90-day time limited trial version. Where 
did you see the code-limited non-expiring version?

Don't get me wrong - I admire ADI and use their parts in a lot of 
applications. If I needed a 600MHz DSP, the Blackfin is the first part 
I'd go to for evaluation. OTOH, the things that I'm doing with DSP don't 
need that kind of speed (yet) and I like using more highly integrated 
MCUs that don't require external memory and peripherals as the Blackfin 
does.

> As for Microchip's dsPIC, they're only 16 bits and most of the application
> examples for these chips I've found on the web were about robotics...
> I'm more interested in realtime FFT...

The 16-bit wordsize can be limiting in some situations (particularly in 
IIR filtering applications), but you might be surprised at how much you 
can do with it. The dsPIC handles FFTs well and includes a number of 
features designed to accelerate that algorithm.

> Is there any other cheap uC with DSP capabilities ? I noticed that AVR is
> marketing DSPs but I'm not sure how they're related to their uCs...

MCUs based on the ARM966es processor like the STR9 family have some DSP 
instructions (MAC, add w/ saturataion, etc) and can be found with peak 
instruction rates approaching 100MHz. You can get fairly inexpensive 
development systems based on those from a number of sources and the 
development tools range from free to a few hundred bucks.

Overall though, a true DSP will run your realtime FFT faster and more 
deterministically than a conventional MCU. The main thing to be aware of 
when jumping into embedded systems development is that if you want to 
minimize your headaches you have to be prepared to shell out for the 
development tools. Reliable eval boards, good download cables (JTAG, 
proprietary, etc) and compilers/IDEs that facilitate your 
edit/compile/debug cycle are crucial and usually aren't free.

Eric