sampling and coefficients
Started by ●April 5, 2005
i am not sure about the sampling frequency of the VC33 DSK
i have run lots of software packages including matlab to generate
coefficients but the sampling frequency does not seem to be anywere
near 48KHz has anybody had any sucess with getting the right
coefficients and bode plot.
I am using a software spectrum analyser with a decent sound card and
goldwave for a frequency sweep and white noise generator.
is it the case that you will never get the filter coefficients spot on
Ralph chasing seems to have got his to work with the old C31.
Jason
Reply by ●April 6, 20052005-04-06
Hi Jason
TI wanted to run the device at its rated speed of 75 Mhz (15 MHz crystal and x5 PLL). Therefor the exact sample rate (when the clock is set for pulse mode) will be 75Mhz/(512*Tprd). Typical usage is to have a sample period of 3 resulting in 48.82813 kHz sample rate. If you want exactly 48 kHz, you will need to pick up a 14.7456 MHz crystal.
If you run the spectrum analyzer application that came with the kit you will find 48.828 kHz is the default Fs and everything is calculated from it. If you click on the sine/siggen button you can fiddle around with a number of settings. If you change the crystal, then these coefficients will be off.
Hope this helps
Keith Larson
DSP and Analog Consulting
Lincoln, Ma 01773
male_uk00 wrote:
TI wanted to run the device at its rated speed of 75 Mhz (15 MHz crystal and x5 PLL). Therefor the exact sample rate (when the clock is set for pulse mode) will be 75Mhz/(512*Tprd). Typical usage is to have a sample period of 3 resulting in 48.82813 kHz sample rate. If you want exactly 48 kHz, you will need to pick up a 14.7456 MHz crystal.
If you run the spectrum analyzer application that came with the kit you will find 48.828 kHz is the default Fs and everything is calculated from it. If you click on the sine/siggen button you can fiddle around with a number of settings. If you change the crystal, then these coefficients will be off.
Hope this helps
Keith Larson
DSP and Analog Consulting
Lincoln, Ma 01773
male_uk00 wrote:
i am not sure about the sampling frequency of the VC33 DSK
i have run lots of software packages including matlab to generate
coefficients but the sampling frequency does not seem to be anywere
near 48KHz has anybody had any sucess with getting the right
coefficients and bode plot.
I am using a software spectrum analyser with a decent sound card and
goldwave for a frequency sweep and white noise generator.
is it the case that you will never get the filter coefficients spot on
Ralph chasing seems to have got his to work with the old C31.
Jason
NEW! You can now post a message or access and search the archives of this group on DSPRelated.com:
http://www.dsprelated.com/groups/c3x/1.php
_____________________________________
Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group.
_____________________________________
About this discussion group:
Archives: http://www.dsprelated.com/groups/c3x/1.php
To Post: Send an email to c...@yahoogroups.com
Other DSP Related Groups: http://www.dsprelated.com/groups.php
