Hi all I hope I came to the right group
My question is general DSP question .
In case I need 2 DSP functions to be done on the same analog signal one after another, for example a low pass filter firs function and on the result a noise reduction function .
My question is : can the 2nd function be done on the digital byte stream of the 1st DSP hardware block , or the 1st output should be filtered and the 2nd DSP function will be done on the analog signal derive from 1 DSP ?
Thanks Elico
RealInfo schrieb:
filtered and the 2nd DSP function will be done on the
Hello,
that is a problem of the sampling frequency and the time needed to compute the first and the second function. If the sampling requency is
40 kHz, one sample must be computed in less than 25 µs. If both functions are done in less than 10 µs for each, it is possible within one DSP, if less than 20 µs you will need two DSPs.Bye
function
be filtered and the 2nd DSP function will be done on the
can it not be 'pipelined' and simply delayed? The first function is a simple low pass, of sorts. Memory would only take enough memory samples to represent the low frequency cutoff, right?
function
filtered and the 2nd DSP function will be done on the
If it's a uP, you don't gain any compute power from pipelining. If it's done in an FPGA, you can pipeline many, many clocks. One can also clock the early stages of a lowpass filter at a higher rate than later ones.
Come to think of it, one can do that in software, too: run the first stage or so more often than later ones.
At any rate (pun!) there's no need for filtering between DSP functions; just stack them up.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
firs function
should be filtered and the 2nd DSP function will be done on the
is
within
done in
early stages
stage or so
just
Just the same, the only real question is can you get all the tasks done on time. This is a simple hard real time thing. OTOH the comm time to hand it off to a second DSP for the next stage may kill the timing.
?-)
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