AN-019

APPLICATION NOTE

TESTING ANDROID SMARTPHONES WITH CLIO

12.5 QC

by Daniele Ponteggia – d[email protected]

INTRODUCTION

In this application note we will show the playback test of Android devices using

minimal effort and tacking advantage of standard phone OS components and

In this application we will use a very simple setup, connecting the DUT to the PC

using the USB cable.

The device under test is a standard Android phone which will be controlled through

Android Debug Bridge (adb) via USB. The DUT should be set up by activating the

Developer Options and connected via USB to the PC.

Instructions on how to configure the device with developer options are available on

developer.android.com at the following link:

https://developer.android.com/studio/debug/dev-options

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– CLIO fw-02 connected via USB

– MIC-02 microphone connected to CLIO fw-02 input A

– DUT connected to PC via USB

This setup is schematically reported in the following figure:

https://developer.android.com/studio/command-line/adb

Once the adb.exe software is installed and the DUT phone connected via USB it is

possible to test the connection using a terminal command

:

>adb devices -l

1 In the examples reported in this document the adb.exe executable PATH has been added

to the Windows environment.

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This adb command should list all the attached Android devices. In our case only one

device is attached, a Motorola Moto G5s, and correctly listed.

There are several actions that can be performed using adb, in this application note

>adb shell ls -l

remotely run the ls -l command on the device, and return the contents of the

root folder of the DUT:

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According to Android documentation

and author's experience the /sdcard/ folder

should be present and accessible.

A part of the internal storage accessible using adb is usually automatically mounted

as sdcard/ into the file system, the contents can be listed using:

>adb shell ls -l sdcard/

As we can see in this case there are already several sub-folders created during SD

send an audio file containing the test signal to the device and instruct the

device to play the audio file. As simple as that.

In particular we will take advantage of Intents. Intents are similar to messages in

the Android OS and are normally used as an high level way of communication

between applications. A more detailed explanation is available browsing the Android

documentation:

https://developer.android.com/guide/components/intents-filters

“An Intent is a messaging object you can use to request an action from another

app component.”

In particular we will use an Explicit Intent to ask the device to play our audio file

an Android device “Primary shared storage (/sdcard) is emulated on top of internal

storage.”. If it is not the case, a folder accessible from adb and applications should be found.

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name of the activity or service you want to start. For example, you might start a new

activity within your app in response to a user action, or start a service to download a file

in the background.”.

Let's prepare a simple test signal using our CLIO 12 system. We can start with a very

simple signal, a sinusodal tone. In CLIO select Sine from the generator and choose the

default values:

The CLIO system will generate a sinusoidal tone at about 1 kHz. If we select “Save

Current Signal” from the generator menu we can store this signal with a .wav

format.

We will call our file “sinetone.wav” and can be saved in a folder which we will use to

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store also our QC testing script.

command:

play the file we just copied:

>adb shell am start -a android.intent.action.VIEW -d

file:///sdcard/sinetone.wav -t audio/* com.google.android.music

The intent can be interpreted as the following instruction sent to the device: open

the file sinetone.wav on /sdcard/ for “view” (listen in our case) using the Google

Play Music application”. This application is pre-installed among other Google

products in many Android devices

.

After a short time, to let the intent (message) to be processed by the Android

system, you should hear a beep coming from the device.

Another application we tested with success is the open source VLC for Android, whose

package name is org.videolan.vlc.

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version but also might be specific to the software installed in the device

.

There is also the chance that, depending on particular device settings, the device

might be locked or in another unknown state. In order to proceed with our testing

device, we needed to make the file stereo in order to be reproduced. This is

device/OS/installed software specific, thus each case must be investigated on its own.

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scenario we must assure that the device is unlocked and showing the home screen:

If this is not the case we can use specific adb commands to get the device to the

home screen.

Here is a partial list of useful adb commands:

Unlock >adb shell input keyevent 82

Swipe up >adb shell input touchscreen swipe 930 880 930 380

Home >adb shell input keyevent 3

880 930 380

If there is still no sound the device volume should be checked. This can be done

physically setting the playback volume using the device controls, or via adb with

the followings command:

>adb shell media volume --get

>adb shell media volume --set 15

The --get option returns the current volume and the range of possible values, the

--set option allows to set the volume into the returned range.

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We suppose now that at this point the device was able to play our beep using the

Google Music Play application.

This will allow to prepare the device to get another playback (actually a VIEW)

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measurement settings should be created and the test signal saved as a .wav file.

Here we note that we selected the R&B and THD option, also note that the Auto

Delay option is set with Max [ms] at 1000 ms, which is the highest value the field

can accept. With the Auto Delay option CLIO system generates a pilot tone at a

given frequency, in this case we left the default value of 10 kHz, which is used by

to find the proper delay value.

The idea, as we did for the MLS&LogChirp test, is to copy the test signal to the

Android Device, send a VIEW intent to reproduce the test signal to the DUT, and

then execute the Sinusoidal measurement with CLIO. The measurement system is

unaware of the fact that the test signal is not generated in real time but instead

With the above settings we can run a dummy measurement. If we left the

microphone connected to CH A and phantom powered, as we did for the previous

example, the measurement will collect ambient noise

. The measurement settings

such as the measurement unit, smoothing and the graphic scales are stored with

the measurement. These settings are used during QC operations. To change the

settings it is needed to save the reference file again.

this case please check that there are no cables connected to CLIO input and switch off

phantom power on measurement channel.

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We save our dummy measurement as “sinusoidal.sin”.

Now we should follow the same procedure to save the sinusoidal test signal, using

the generator menu we choose “Save Current Signal” as “sinusoidal.wav”.

downward frequency sweep.

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We can copy the signal to the device storage:

file:///sdcard/sinusoidal.wav -t audio/* com.google.android.music

We should hear the device playing the usual sinusoidal sweep ranging from high

frequency down to low frequency, with a short beep at the beginning used for

synchronization.

In the case of the specific device under test in this application note we clearly hear

that the signal has a dropout. This happens due to the non-invariant nature of the

DUT which is engaging some form of transducer protection by limiting the output

power. This is not acceptable in our test, the only chance we have is to lower the

output volume, and achieve this with the adb command:

We are now ready to prepare a QC script to perform the measurement:

[GLOBALS]

COMPANY=AUDIOMATICA SRL

TITLE=ANDROID PLAYBACK RESPONSE PLUS THD AND RUB+BUZZ

[PERFORM]

EXTERNAL=INTENTSIN.BAT

DELAY=1000

[SIN]

OUT=1.000 V

INA=-40

INB=0

adb shell am start -a android.intent.action.VIEW -d

file:///sdcard/sinusoidal.wav -t audio/* com.google.android.music

The stop.bat is the same as in the previous example.

In this example we would like to show the response alongside THD

thus a simple

limits file (limits.lim) is needed:

[RELATIVE]

FREQJITTER=0.16

8 Rub'n'buzz curve is measured but not displayed.

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[UPPER LIMIT DATA]

200 3

Let's run the QC test for the first time, this will lead to create the real reference

measurement, since the one we used was done without the DUT. This first

measurement will also help to understand if the QC script timing is correct and if

there are modifications of the script delay to be carried out.

We should probably get a BAD result, since the frequency response in the current

reference measurement is only noise. Nevertheless we should see the response and

THD curves:

Now we can release the measurement from the QC menu, open the Sinusoidal

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Let's focus on the delay calculated by the Auto Delay procedure, this value in ms

gives us an idea of the timing of the script.

The following diagram can help to understand the timing of the whole procedure:

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introduced by the playback through intent is not completely predictable

, but a CH

A delay of about 250 ms tells us that the QC script delay value is sufficient and

leaves space for some uncertainty in the Android latency.

We can save the Sinusoidal response file overwriting the sinusoidal.sin reference

10 In this stage it is possible to adjust the x and y axis range of the frequency response

plot, the new settings will be saved with the measurement and applied to QC operations.

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While working on this application note we sadly found out that the Google Play

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