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Hello all, How to test FFT for a realtime signal on ADSP-2181 processors ? I also want to know is it possible to display the FFT of real time signal on LCD screeen (I mean frequency values) ? Has any one in the group tried out tht ? i:e I want to display the contents tht are present in the Realtime signal. LCD is comparatively slow device compared to DSP. In case if DSP is writing the data fastly to LCD wht may be the possible solution to overcome tht ? Thanks and regards Girish ________________________________________________________________________ Yahoo! Messenger - Communicate instantly..."Ping" your friends today! Download Messenger Now http://uk.messenger.yahoo.com/download/index.html |
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Testing FFT
Started by ●July 2, 2004
Reply by ●July 2, 20042004-07-02
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On Fri, 2 Jul 2004, [iso-8859-1] Girish wrote: > Hello all, Howdy Girish, > How to test FFT for a realtime signal on ADSP-2181 > processors ? > > I also want to know is it possible to display the > FFT of real time signal on LCD screeen (I mean > frequency values) ? > > Has any one in the group tried out tht ? Nope, but I can give you some ideas. > i:e I want to display the contents tht are present in > the Realtime signal. > > LCD is comparatively slow device compared to DSP. > > In case if DSP is writing the data fastly to LCD wht > may be the possible solution to overcome tht ? First figure out the data rate to the LCD. How many cycles between bytes are there, and how many cycles do you take to send the byte? It's probably on the order of 1 to 2% (.01 to .02 send/inbetween). Then figure out how many bytes you want to send. The total time it takes to display the picture is your Block Time. How many samples can you collect and process during a Block Time? That depends on the A/D, how big your FFT is and how fast your processor is. So the main idea is - collect data, perform fft and send results to LCD _all at once_. 3 internal buffers (or however many it really takes) will be useful. If the data collection and send to LCD are interrupt driven, then the FFT computation is foreground (along with assundry book keeping). If you can do this, the LCD will be updated at the fastest possible rate, the display will be "real time", and you'll be pushing your DSP to it's max possible limits. Should be challenging and fun! Patience, persistence, truth, Dr. mike |
