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Real-Time Labs

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Android Steps

6.5. REAL-TIME LABS 207

screen d to this range (10–200 m) as control parameters. Assume the constant of proportionality

is 10

3

, and the electric ﬁeld strength at the diﬀraction screen is 1 V/m.

Now replace the slit with two slits, each 0.1 mm in width, separated by 1 mm (center-

to-center), and centered on the optical axis. Plot the intensity of light in the viewing screen by

setting the parameters as controls.

6.5 REAL-TIME LABS

LR6_2 – is real-time lab is a noise reduction application. e input signal is modulated with

a tone at fs/5 then noise is added to it. One should be able to choose the output to plot. e

choices are z2, the modulated input signal z3, the modulated input signal with noise y1, the ﬀt

of the original signal y2, the ﬀt of the modulated signal y3, the ﬀt of the modulated signal with

noise y4, the noise removed version of y3 and y4, the noise removed version of y3 and z4, and

the inverse ﬀt of the noise removed signal.

6.5.1 ANDROID STEPS

ese steps modify the LR5_2 lab. Copy the LR5_2 directory to LR6_2 and rename the LR5_2

ﬁles to LR6_2. Update the project ﬁles before updating the codes.

1. Update the applicationId in app/build.gradle to have LR6_2 in the name instead of

LR5_2. Remove the old C code from app/src/main/jni and copy the new MATLAB gen-

erated code into the same directory.

2. Update the MATLAB generated ﬁles in the ﬁle CMakeLists.txt. e section in the ﬁle

should look like the following block of code. e order of the ﬁles does not matter.

add_library( # Sets the name of the library.

matlabNative

# Sets the library as a shared library.

SHARED

# Provides a relative path to your source file(s).

src/main/jni/abs.c

src/main/jni/abs.h

src/main/jni/eml_rand_mt19937ar_stateful.c

src/main/jni/eml_rand_mt19937ar_stateful.h

src/main/jni/fft.c

src/main/jni/fft.h

src/main/jni/fftshift.c

208 6. CONTINUOUS-TIME FOURIER TRANSFORM

src/main/jni/fftshift.h

src/main/jni/ipermute.c

src/main/jni/ipermute.h

src/main/jni/LR6_2.c

src/main/jni/LR6_2.h

src/main/jni/LR6_2_data.c

src/main/jni/LR6_2_data.h

src/main/jni/LR6_2_emxAPI.c

src/main/jni/LR6_2_emxAPI.h

src/main/jni/LR6_2_emxutil.c

src/main/jni/LR6_2_emxutil.h

src/main/jni/LR6_2_initialize.c

src/main/jni/LR6_2_initialize.h

src/main/jni/LR6_2_rtwutil.c

src/main/jni/LR6_2_rtwutil.h

src/main/jni/LR6_2_terminate.c

src/main/jni/LR6_2_terminate.h

src/main/jni/LR6_2_types.h

src/main/jni/MatlabNative.c

src/main/jni/rand.c

src/main/jni/rand.h

src/main/jni/rtGetInf.c

src/main/jni/rtGetInf.h

src/main/jni/rtGetNaN.c

src/main/jni/rtGetNaN.h

src/main/jni/rtwtypes.h

src/main/jni/rt_nonfinite.c

src/main/jni/rt_nonfinite.h

)

3. Moving onto app/src/main/AndroidManifest.xml, update the LR5_2 names to LR6_2.

4. e ﬁle app/src/main/res/xml/prefs.xml will need to be edited to remove the resistance,

capacitance, frequency, and output settings similar to the previous labs. is time a List-

Preference of the output choice is made:

ListPreference

android:key=''choice1''

android:title=''What to plot?''

6.5. REAL-TIME LABS 209

android:summary=''Default: z2''

android:defaultValue=''0''

android:entries=''@array/choiceOptions''

android:entryValues=''@array/choiceValues'' />

Since the array references, @array/choiceOptions and @array/choiceValues ,

are used, they need to get added to the ﬁle app/src/main/res/values/arrays.xml. Remove

systemOptions , systemValues , choiceOptions , and choiceValues .

string-array name=''choiceOptions''>

</string-array>

<string-array name=''choiceValues''>

</string-array>

5. Moving on to the code changes, update the ﬁle

app/src/main/java/com/dsp/matlab/Filter.java for the function calls by adding resistance,

capacitance, frequency, and display choice,

currentFrame.setFiltered(Filters.compute(currentFrame.getFloats(),

Settings.Fs,

Settings.choice, Settings.blockSize));

6. Now, in the ﬁle app/src/main/java/com/dsp/matlab/Filters.java, update the compute

method as follows:

210 6. CONTINUOUS-TIME FOURIER TRANSFORM

public static native float[] compute( float[] in, int Fs,

int choice, int frameSize );

7. To make sure the coeﬃcient input is applied to the settings, update the

updateSettings() method in app/src/main/java/com/dsp/matlab/RealTime.java

and add the following line within. e previous settings for resistance, capacitance,

coeﬃcients, frequency, and system can be removed.

Settings.setChoice(Integer.parseInt(

preferences.getString("choice1","0")));

8. Update app/src/main/java/com/dsp/matlab/Settings.java to store and retrieve the settings

added. Again the resistance, capacitance, coeﬃcients, frequency, and system-related vari-

ables and methods can be removed.

public static float choice = 0;

public static void setChoice(int choice1){choice=choice1;}

9. Finally, update the app/src/main/jni/MatlabNative.c interface ﬁle. is ﬁle is the interface

from Java to native C. e entire ﬁle is listed below.

#include <jni.h>

#include <stdio.h>

#include ''rt_nonfinite.h''

#include ``LR6_2.h''

#include ``LR6_2_terminate.h''

#include ``LR6_2_emxAPI.h''

#include ``LR^_2_intialize.h''

jfloatArray

Java_com_dsp_matlab_Filters_compute(JNIEnv *env, jobject this,

jfloatArray, input, jint Fs, jint choice, jint frameSize)

{

jfloatArray output = (*env)->NewFloatArray(env, frameSize);

float *_in = (*env)->GetFloatArrayElements(env, input, NULL );

//compute

emxArray_real32_T *result;

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