Number of bytes receives not the same after each cycle

[kuzulis]

with this code, i will lose some packets no ?

No. All data will be saved (accumulated) in internal buffer of class in background. So, you can read data in any time (even without readyRead() signal, e.g. by a signal from QTimer or by button clicked and so on).

[AUDI_ENG]

Finally You saw the problem First question : can you change the controller software ? Second : the data in the package are binary (bytes in the range 00 - FF) ?

Yes, I can change the software in ther sender (Assembly langage) and the data in the package are binary ( 00 - FF) but the data can't be over ~ 400(int) = 190 'H'
I'm thinking to send 2 bytes in the begininning of each package : for exemple A1 - A2 - A3 - A4 .. A16 instead of 01 - 02 - 03 -04 ... 16

---

Added after 10 minutes:

No. All data will be saved (accumulated) in internal buffer of class in background. So, you can read data in any time (even without readyRead() signal, e.g. by a signal from QTimer or by button clicked and so on).

Hi,

I'm testing the code, its work perfectly. So, I have 9 bytes after each cycle, but the beginning of the package is not the ID, it's the last byte :
for example :
byte 8__byte ID__ byte 1__ byte 2__ byte 3__ byte 4__ byte 5__ byte 6__ byte 7
17______01______0D_____ 09_____ 17_____ 08_____ 09_____ 08_____ 08
17______02______0D_____ 09_____ 17_____ 08_____ 09_____ 08_____ 08
17______03______0D_____ 09_____ 17_____ 08_____ 09_____ 08_____ 08
17______04______0D_____ 09_____ 17_____ 08_____ 09_____ 08_____ 08
.................................................. .................................................. .............;

The problem is related to the detection of the beginning of package ?

[Lesiok]

And this is good idea - create a frame with marker.
According to me it would look like this : AA AA id_0 id_1 d_0 d_1 d_2 d_3 d_4 d_5 d_6 d_7 d_8

[AUDI_ENG]

Foo::readyRead()
{
    static const int expectedPacketSize = 9; // your 9 bytes
    if (port->bytesAvailable() < expectedPacketSize)
        return; // do nothing
    QByteArray data = port->read(expectedPacketSize);
 
    // do domething processing of your packet
}

Foo::readyRead()
{
    static const int expectedPacketSize = 9; // your 9 bytes
    if (port->bytesAvailable() < expectedPacketSize)
        return; // do nothing
    QByteArray data = port->read(expectedPacketSize);
 
    // do domething processing of your packet
}

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Of course, I'm skip the parsing and synchronization of incoming packets from an incoming data stream.

the code works perfectly but I like to understand it deeply, can you explain me how it works, for exemple how it detects 9 bytes without losing data

Thank you

---

Added after 4 minutes:

And this is good idea - create a frame with marker.
According to me it would look like this : AA AA id_0 id_1 d_0 d_1 d_2 d_3 d_4 d_5 d_6 d_7 d_8

Thank you,

but why I want to repeat id_0 id_1 twice ? and you meaning that AA AA , id_0 8bytes , id_1 8bytes , id_2 8bytes...... ??

[Lesiok]

Thank you,
but why I want to repeat id_0 id_1 twice ? and you meaning that AA AA , id_0 8bytes , id_1 8bytes , id_2 8bytes...... ??

If id is one byte send only one of course. I thought that id is 2 bytes.
And NO, I mean : AA AA id_0 8 bytes, AA AA id_1 8 bytes.... Every packet starts with 2 bytes marker AA AA.

[AUDI_ENG]

If id is one byte send only one of course. I thought that id is 2 bytes.
And NO, I mean : AA AA id_0 8 bytes, AA AA id_1 8 bytes.... Every packet starts with 2 bytes marker AA AA.

Ok, i will try this : AA AA id_0 8 bytes , AA AA id_1 8 bytes ...
in Qt application I will change things in the code no when i read data?

[Lesiok]

As we said earlier : collect data into the buffer and then analyze them searching for frame start tag (bytes AA AA). Remember that the frame is 11 bytes no 9.

[AUDI_ENG]

As we said earlier : collect data into the buffer and then analyze them searching for frame start tag (bytes AA AA). Remember that the frame is 11 bytes no 9.

I used this code :

Foo::readyRead(){

static const int expectedPacketSize = 11; // your 11 bytes
if (port->bytesAvailable() < expectedPacketSize)
return; // do nothing

QByteArray data = port->read(expectedPacketSize); // do domething processing of your packet
}

so I have 11 bytes in the data buffer but how I can detect the start of the packet , in the same time when I read data ?
I can't analyse my packet for detecting data after reading, and if I collect all data in the same buffer, its very heavy for application

[Lesiok]

You should declar variable dataBuffer in class Foo and then do something like this :

Foo::readyRead(){
int frameLen = 11;
dataBuffer.append(port->readAll());
if( dataBuffer.size() < frameLen )
    return;// data to short
int indexOfFrame = dataBuffer.indexOf("\xAA\xAA");
if( indexOfFrame < 0)
    return;// frame marker not found
QByteArray oneFrame = dataBuffer.mid(indexOfFrame,frameLen);// we have one frame, do something with this
dataBuffer = dataBuffer.right(indexOfFrame,frameLen);//remove processed data from the buffer
}

Foo::readyRead(){
int frameLen = 11;
dataBuffer.append(port->readAll());
if( dataBuffer.size() < frameLen )
    return;// data to short
int indexOfFrame = dataBuffer.indexOf("\xAA\xAA");
if( indexOfFrame < 0)
    return;// frame marker not found
QByteArray oneFrame = dataBuffer.mid(indexOfFrame,frameLen);// we have one frame, do something with this
dataBuffer = dataBuffer.right(indexOfFrame,frameLen);//remove processed data from the buffer
}

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[AUDI_ENG]

I'm writing this code before your code, because with yours I'm losing data

if(Port->bytesAvailable() < lenFram){
 
      return; 
}
dataBuffer.append(port->read(lenFram)); // I change your line to this

if(Port->bytesAvailable() < lenFram){

      return; 
}
dataBuffer.append(port->read(lenFram)); // I change your line to this

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When I'm adding this before your code I have :

bytesreceives = "0aaaaa0c1209080a090908"
index TAG = 1
nb data read = 10 bytes = "aaaa0c1209080a090908"

bytesreceives = "0aaaaa0d0a09090a090909"
index TAG = 1
nb data read = 10 bytes = "aaaa0d0a09090a090909"

bytesreceives = "0aaaaa0e0e09080a080909"
index TAG = 1
nb data read = 10 bytes = "aaaa0e0e09080a080909"

_________________________________________________

with your code (with readAll() ) : I have this :

nb data read = 11 bytes = "aaaa070a09080a0908090a"
nb data read = 11 bytes = "aaaa080a08090a0909080a"
nb data read = 11 bytes = "aaaa0a1709090a0809090a"
nb data read = 11 bytes = "08090aaaaa0d0a08090a09" --> AA is not in the beginning
nb data read = 11 bytes = "09080aaaaa0f1709090a08" --> AA is not in the beginning
nb data read = 11 bytes = "09080aaaaa020a08090a09" --> AA is not in the beginning
nb data read = 11 bytes = "aaaa031209090a0908090a"
nb data read = 11 bytes = "aaaa041209090a0908090a" --> ID = 4
nb data read = 11 bytes = "08090aaaaa070e08090a09" --> AA is not in the beginning (ID = 7) ---> I miss data with ID = 5 and 6
nb data read = 11 bytes = "08090aaaaa091209080a09" --> AA is not in the beginning
nb data read = 11 bytes = "09090aaaaa0b0a09080a09" --> AA is not in the beginning



I have still the problem with the beginning of frames, sometimes, it is AAAA and sometimes other bytes of frames

[Lesiok]

Between lines 8 and 9 of my code should be :

if( (dataBuffer.size() - indexOfFrame) < frameLen )
    return; // frame is not complete

if( (dataBuffer.size() - indexOfFrame) < frameLen )
    return; // frame is not complete

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Line 10 sholud be :

dataBuffer = dataBuffer.right(indexOfFrame+frameLen);//remove processed data from the buffer

dataBuffer = dataBuffer.right(indexOfFrame+frameLen);//remove processed data from the buffer

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I have not tested my code. This is just an example of how something should look.

[AUDI_ENG]

Between lines 8 and 9 of my code should be :

if( (dataBuffer.size() - indexOfFrame) < frameLen )
    return; // frame is not complete

if( (dataBuffer.size() - indexOfFrame) < frameLen )
    return; // frame is not complete

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Line 10 sholud be :

dataBuffer = dataBuffer.right(indexOfFrame+frameLen);//remove processed data from the buffer

dataBuffer = dataBuffer.right(indexOfFrame+frameLen);//remove processed data from the buffer

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I have not tested my code. This is just an example of how something should look.

I have always 11 bytes and the beginning AAAA (working perfectly)
but I have still the problem about losing data, its normal to losing data (because somtimes the nombre of bytes availables is more then 22 for exemple --> so I lost one frame) ??