I am looking for an embedded DSP board/system with a (14 or 16 bit)
ADC which
will be able to sample a +/- 3V signal at 40KHz and perform 256 point
FFTs. (preferably in
real time)  The system will sample the data for 1 minute, summing the
128 point FFT results.

The system should be small enough to fit into the inside a 3" diameter
Schedule 80 plastic pipe.

The system should consume less than 25mA while sampling and
processing.

The system should be commanded through a 3-line (Transmit, Receive,
Ground) UART.

This system will be used to sample data from a hydrophone mounted at
10m below the
surface of the ocean.  The signal from the hydrophone is already
preamplified and
anti-alias filtered at 23KHz.


The system I am currently using is a board which is run by way of a
12V alkaline
battery pack.  A switched regulator on board reduces this voltage to
5V.
It consumes about 150 mA when it is sampling/processing the data.
The DSP chip used is the C33 from TI.  This chip does not have enough
RAM to
run 256 point FFT code in RAM, which would speed up FFT processing
time.  Because of
this the time it takes to process a 256 point FFT is about the same as
the time
it takes to sample the data.  If I could simply perform the FFT on the
previous
set of 256 points while sampling the next 256 points I could cut the
power consumption
of my system in half, as the system would only be on about half as
long.  The C33 is
also a 5V device.  I could also reduce my battery requirements if the
chip ran at 3.3V
or below.

Traquair at www.traquair.com produces a line of DSP boards utilizing
the C6000
from TI, but these boards are a bit higher end than I require.  I
believe they
consume too much power.  My requirements would be filled using the
TI C5400 line of DSP processors.  Traquair makes a TI C32 board, but
this is the
chip I currently use and it also consumes too much power.

Answer the following questions:

- Are there any "off the shelf," solutions which would work for me?
- Is the TI C5400 line an appropriate choice?
- If not, what DSP chip would work better?
- Are there any DSP developers out there who have already created
systems
close to this which may be able to modify an existing design which
would
meet my specifications?