dsp/fft. Help with simple design

You won't find any uC (internal A2D) fast enough to match the AD5933. What's wrong with the 2 chips design?

I'll bet you can do with just the AD5399 and a i00Hz crystal oscillator.

Jerry

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Yes, a three chips solution:

AD5933, AD5399 and XC3S1000 should work.

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The speed is not the most important issue, overall size is. It doesn't need to be "real time" fft. It is okay, if we just send a sine for a few ms and then use a few seconds processing the result.

Hi John,

How about something like TI's MSP430F155? It has on-board 12-bit ADC and DAC, is very low-power, and enough MIPS to do the simple DSP tasks you ask for.

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That looks very interesting. I'll give that one a check. Thanks

Be aware that it can probably do a few hundred KSPS at best, not MSPS.

DAC,

It's an 8 MHz part - you can probably get 1 MSPS out of it, if you're just outputting to a DAC and collecting input from a ADC. Note that it has DMA, so you won't waste cycles transferring data.

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I went and checked out the data sheet, do not count on more than about 250 k samples / second. Try a real DSP of the TMS320c5000 series.

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Try the analog devices microcontroller ADUC70XX

lower price then MSP430 ($5), with much better analog (1 MHz 12 bit A/D same as the AD5933, and 12 bit DAC) and a much better processor (32 bit

40MHZ ARM), a FFT is no problem with chip, they come in small 6x6 mm packages too, down side is it takes more power then the MSP430, (11mA At 5Mhz, 40mA at 40Mhz), but if you can afford the power this would be a better choice

sure you can, the Analog Devices ADUC70XX uC has a better A/D then the AD5933

And even though the package is prototype-unfriendly, there's a $30 "mini kit" which has the ADuC7020 on a 40 pin DIP sized board. I found it while looking for discrete DACs for a microcontroller project. The Analog part really takes the analog parts (sorry) much more seriously than a typical microcontroller. They don't multiplex the ADC and DAC pins with GPIOs. The ADC performance is way beyond typical micros.

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Hey Ben,

These look like really cool parts. Thanks for bringing them to my (our) attention.

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sparkfun.com also has them in DIP sized boards

The Analog part

Yes, the ADuCs are basically A/D's with processors added on, while most micros add the A/D's on as a afterthough. All the ADuC's A/D characteristics are spec at full processor speed, including noise, the MSP430 datasheets don't even specify noise or even input bandwidth of it's A/D, well at least I couldn't find them, the MSP430 is still a nice chip though, very low power.