Mobile and Embedded

Hi @TyChapin,

Upon connection, the MTU is set to the default value of 23.

That's only a "we don't know yet" default, which is, frankly, pretty meaningless. As per the docs:

Before the connection setup and MTU negotiation, the default value of 23 will be returned.

@TyChapin said in BLE MTU Exchange:

Then once I connect to a service, the MTU is 256 which is what the BLE device wants it to be at.

Yep, that (256) would be the real, negotiated, MTU.

@TyChapin said in BLE MTU Exchange:

When I go to read the characteristic value that has 64 bytes, only 24 bytes come over.
Does anyone have any advice on how to exchange the MTU size properly?

I suspect the problem is not MTU related. In most cases, the MTU should not affect the characteristic data size (just performance), because the BLE stack will use as many MTU's as needed to transfer the characteristic's data.

How are you checking the characteristic value's length? ie how do you know that the "value has 64 bytes", and "only 24 bytes come over"?

(Also, if its a publicly documented characteristic, and you're able to share the UUID, that might help, but no worries if not).

Cheers.

Hello @jsulm I have looked deeper into my problem and found some things. Could you help me by confirming as far as you can? Or recommend someone that may know the answer?

I found a new documentation page I hadn't read: https://doc.qt.io/qt-5/ssl.html#enabling-and-disabling-ssl-support
When I launched the configure program with the openssl-linked option, I finally got a QtNetwork/qtnetwork-config.h file without the definition that caused trouble (see above). However, when I tried to save the new qmake version and its Android kit, I get an error saying that the Android Clang compiler "can't produce code for the Qt version "Qt 5.15.13 (Qt-5.15.13)" (x86-linux-generic-elf-64bit)."

What I understand is that I didn't activate the target for cross-compilation in the initial configuration step.
So I went back and launched this

OPENSSL_LIBS='-L~/android-sdk/android_openssl/ssl_1.1/arm64-v8a/include -lssl -lcrypto' \ ~/qt5/configure -openssl-linked -prefix /opt/Qt5.15 -xplatform android-clang \ -disable-rpath -nomake tests -nomake examples -android-ndk ~/android-sdk/ndk/21.3.6528147 \ -android-sdk ~/android-sdk -no-warnings-are-errors -opensource -confirm-license

But I got the following error:

ERROR: Feature 'openssl-linked' was enabled, but the pre-condition '!features.securetransport && !features.schannel && libs.openssl' failed. Check config.log for details.

Please note that when I launch the mentioned command without -xplatform android-clang, it seems to work and I am asked to launch gmake. So for the time being I have found myself in an incompatibility of installing an SSL-supported Qt and cross-compiling for Android.

Regarding the config log file that the error indicates me, I don't know what exactly to look at.
What I find interesting is that at some point there is this SSL-related error (with the -xplatform option):

+ cd /home/diego/qt-build/config.tests/openssl && MAKEFLAGS= /usr/bin/gmake clean && MAKEFLAGS= /usr/bin/gmake > rm -rf /home/diego/qt-build/config.tests/openssl/android-build > rm -f main.o > rm -f *~ core *.core > /home/diego/android-sdk/ndk/21.3.6528147/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ -c -target aarch64-linux-android21 -fno-limit-debug-info -fPIC -fstack-protector-strong -DANDROID -O2 -fPIC -I. -I/home/diego/qt5/qtbase/mkspecs/android-clang -o main.o main.cpp > main.cpp:2:10: fatal error: 'openssl/ssl.h' file not found > #include <openssl/ssl.h> > ^~~~~~~~~~~~~~~ > 1 error generated. > gmake: *** [Makefile:193 : main.o] Erreur 1

The weird thing is that without the -xplatform option, I don't see this error, and yet the two command lines are otherwise the same one.

Apart from that, there are many other errors, but as I said I don't know exactly what to look at.

@Bonty said in Button over QVideoWidget:

but its not the same in Qt6

What does this mean exactly? What happens in Qt6?

@Gautham0517 said in Memory allocation Issue in Raspberry pi 4b 8GB Ram:

GEM: F/E May 01 02:24:08.671 <Platform>gp::MemMgr::AllocFail Out of memory allocating

The Raspberry is out of memory, I'd say.

@JonB
Thank you for your replies.
I tried by removing all signal & slot connections.
In function ‚‘void CwWindow::show_recPo(double dB)‘ the
result was ‚‘0‘ instead of the correct value (-49.3). The difference
to with signal & slot was that ‚‘0‘ did not move to the left.

In function ‚‘void CwWindow::updatef()‚‘ the resultat also is ‚‘0‘ .)))

@Vince_SiriusXM it's described here.

@misarb B2QT being a commercial product you can also ask Qt Company for support

@Krishnakumar-Pathivuraj if you are using a fixed version of Qt, why not just get the source archive for that version rather than recloning ?

Hi All,

I'm also new to this topic,

I used the same intent defintion in androidmanifest xml file but Android is not considering my app to be a launcher app (nothing happens when I press on home button)

<activity android:name="org.qtproject.qt.android.bindings.QtActivity" android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|layoutDirection|locale|fontScale|keyboard|keyboardHidden|navigation|mcc|mnc|density" android:label="-- %%INSERT_APP_NAME%% --" android:launchMode="singleApp" android:screenOrientation="unspecified" android:exported="true"> <intent-filter> <action android:name="android.intent.action.MAIN"/> <category android:name="android.intent.category.HOME"/> <category android:name="android.intent.category.DEFAULT"/> </intent-filter> <meta-data android:name="android.app.lib_name" android:value="-- %%INSERT_APP_LIB_NAME%% --"/> <meta-data android:name="android.app.arguments" android:value="-- %%INSERT_APP_ARGUMENTS%% --"/> <meta-data android:name="android.app.extract_android_style" android:value="minimal"/> </activity> <provider android:name="androidx.core.content.FileProvider" android:authorities="${applicationId}.qtprovider" android:exported="false" android:grantUriPermissions="true"> <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/qtprovider_paths"/> </provider> </application>

Hello, I have also encountered this issue. Is it okay for me to use the plist file in the Qt Bluetooth shared folder? Once I try to modify the plist file, I will encounter the same error as you. Has your problem been resolved?

@mj01 Up to you to use or not to use debugger to get more information about your issue, I'm out...

@MG33 I already told you what you're doing wrong. Just read it and act accordingly instead of repeating same information again and again.
Accumulate data in a buffer until you got a complete package and then parse it and update your UI.