Forrest Sheng Bao <Engineering our dreams>

by Forrest Sheng Bao http://forrest.bao.googlepages.com

I have to say that ATMEL is the most Linux-friendly company among all MCU/DSP makers in the world, followed by TI. Both TI and ATMEL use tons of open source toolchains so Linux zealots can build their apps on Linux.

I learned how to play with AVR 8-bit instruction set when I was an undergraduate. Now, I am gonna use AVR32, which is a 32-bit instruction set.

Here is some good information:
AVR32 32-bit MCU - Tools & Software: http://www.atmel.com/dyn/products/tools.asp?family_id=682#1443
ATEVK1100 development kit: http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4114 only $129

by Forrest Sheng Bao http://fsbao.net

I am doing a take-home midterm test of a class I am taking. So, I decided to use Python to to it. Below is a code for one problem. It includes several frequency used functions in classical signal spectral analysis and FIR filter design. The problem itself is to design bandpass filters over alpha to theta bands and apply them onto a EEG series, and plot the time domain and frequency domain signal, as well as the frequency response of filters. I used window methods to design FIR bandpass filters. The filters coefficients are smoothed by a Kaiser window. Filtering is implemented by convolving original signal with coefficients of filters.

by Forrest Sheng Bao http://fsbao.net

I can't run sicstus Prolog on my department Solaris workstation. That makes me very unhappy at 3 am. So I decide to use gprolog. And the programming can be easier. In gprolog, FD is built-in.

Factorial in gprolog:

factorial(0,1). 

factorial(N,F) :-  
   N>0, 
   N1 is N-1, 
   factorial(N1,F1), 
   F is N * F1.

Summation in gprolog

sum(0,0). 

sum(N,F) :-  
   N>0, 
   N1 is N-1, 
   sum(N1,F1), 
   F is N + F1.

It seems that "is" is also a built-in predicate in swi-prolog.

by Forrest Sheng Bao http://fsbao.net

The code below is an example on using spectrogram function of MATLAB to compute STFT of a chirp signal, which changes frequency from 10 Hz to 200 Hz in 1 second. Both Hamming and Chebychev windows are used. Different window length has been tried, 128, 64 and 32.

by Forrest Sheng Bao http://fsbao.net

There are some great books I always want too read. Following books are so famous that you can find them in online bookstore so easily. I cannot guarantee that you can find them in local bookstores coz they won't be as popular as movie stars' biographies. But they will definitely be in stock in next hundreds of years whereas movie stars' biographies will be dust in next 100 years.

General
The Analects by Confucius and his disciples

Is there a God? Or, are there Gods?
The Varieties of Scientific Experience: A Personal View of the Search for God by Carl Sagan
The Language of God: A Scientist Presents Evidence for Belief by Francis Collins
Things A Computer Scientist Rarely Talks About by Donald E. Knuth

Mathematics

by Forrest Sheng Bao http://fsbao.net

% Copyleft (C) Forrest Sheng Bao 1984-2009 http://fsbao.net
% with Dept. of Electrical and Computer Engineering and Dept. of Computer Science, Texas Tech University, Lubbock, Texas, USA
%
% This program shows the orders and frequency/phase properties of four different kinds of filters, Butterworth, Chebyshev Type I, Chebyshev Type II and Elliptic.
% The filter is expected to have a cutoff frequency at 200 Hz with attenuation 40 db/octave. The sampling frequency is 2000 Hz.
%
% This program licensed in GNU GENERAL PUBLIC LICENSE (GPL) v3 or later.
% If you do not know what GNU GPL is, please visit http://www.gnu.org/copyleft/gpl.html

A friend asked me an interesting question: Why is Z-transform always related to digital filter design? Well, this is interesting. But the clue is simple.

You need a web browser that supports MathML to read this doc. To see whether your browser supports it, please check whether you can see formulas on this page. By default, Linux and Mac user should be able to make it from their Mozilla Firefox browser. For Windows users, well, that's not a question you should ask me.

The author cannot guarantee this article has no typo. Please confirm all equations before you use them.

by Forrest Sheng Bao http://fsbao.net

You need a web browser that supports MathML to read this doc. To see whether your browser supports it, please check whether you can see formulas on this page. By default, Linux and Mac user should be able to make it from their Mozilla Firefox browser. For Windows users, well, that's not a question you should ask me.

The author cannot guarantee this article has no typo. Please confirm all equations before you use them.

There are so many guys asking me the difference between DTFT and DFT. And, they confused these two concepts with FFT and STFT.