DSP/BIOS and RTDX Using MATLAB, Visual C++, Visual Basic, and LabVIEW - Digital Signal Processing and Applications with the C6713 and C6416 DSK - page 316

% RTDX_MATLABFFT.m MATLAB-DSK interface with loop. Calls CCS,
%loads .out file. Data from DSK MATLAB for FFT and plotting

ccsboardinfo %board info
cc=ccsdsp('boardnum',0); %setup CCS object
reset(cc); %reset board
visible(cc,1);

%for CCS window

enable(cc.rtdx); %enable RTDX

if ~isenabled(cc.rtdx);
error('RTDX is not enabled')
end
cc.rtdx.set('timeout', 20); %set 20sec timeout for RTDX
open(cc,'rtdx_matlabFFT.pjt'); %open project
load(cc,'./debug/rtdx_matlabFFT.out'); %load executable file
run(cc); %run program

configure(cc.rtdx,1024,1); %configure one RTDX channel

open(cc.rtdx,'ochan','r'); %open output channel

pause(3) %wait for RTDX channel to open

fs=16e3; %set sample rate in MATLAB

fftlen=256; %FFT length

fp=[0:fs/fftlen:fs/2-1/fftlen]; %for plotting within MATLAB

enable(cc.rtdx,'ochan'); %enable channel from DSK

isenabled(cc.rtdx,'ochan');
for i=1:2048 %obtain 2048 buffers then stop
outdata=readmsg(cc.rtdx,'ochan','int16'); %read 16-bit data from DSK
outdata=double(outdata); %32-bit data for FFT
FFTMag=abs(fftshift(fft(outdata))); %FFT using MATLAB
plot(fp,FFTMag(129:256))
title('FFT Magnitude of data from DSK');
xlabel('Frequency');
ylabel('Amplitude');
drawnow;
end
halt(cc); %halt processor
close(cc.rtdx,'ochan'); %close channel
clear cc %clear object
FIGURE 9.9. MATLAB program that runs on the host PC to illustrate RTDX with
MATLAB. MATLAB's FFT and plotting functions are used ( rtdx_matlabFFT.m ).

This creates an input channel, waits for the input channel to be enabled, and reads
the data (input to the C6x on the DSK). In the MATLAB program, the following
lines of code

open(cc.rtdx,' ichan', ' w' );
enable(cc.rtdx,' ichan' );
writemsg(. . .);

open and enable an input channel and then write (send) the data from MATLAB
running on the host PC to the C6x on the DSK. See Example 9.4.