QSerialPort data missing while reading

[biomed12]

Hello,

I am tring to get data over serial port with my desktop program.

Data is corrupted many times like below (I except always 0 data)

"266"
"10"
"10"
"10"
"10"
"10"
"3"
"3"
"2"
"2"
"0"
"0"
"0"
"0"
"2"
"2"
"4"
"4"
"0"
"0"
"4"
"4"
"0"
"0"
"0"
"0"
"0"

Device side code is:

//uart send function
void UARTSend(uint32_t ui32UARTBase, const uint8_t *pui8Buffer, uint32_t ui32Count)
{
    while(ui32Count--)
    {
        UARTCharPut(ui32UARTBase, *pui8Buffer++);
    }
		
}

Qt side is:

union{
    unsigned char bytes[2];
    unsigned int integerPart;
    unsigned char *ptr;
}serData;

void MySoftware::serialReadData()
{
    //read all data
     serialInData = serial->readAll();

//assign it to union
    serData.bytes[0] = (unsigned char)serialInData[0];
    serData.bytes[1] = (unsigned char)serialInData[1];

//debug
    qDebug()<<QString::number(serData.integerPart);

}

note: I used qSerialExamples. I saw some topic which is related with my problem but, there was no certain solution.

[SGaist]

Hi and welcome to devnet,

How are you configuring your serial port ?

What do you mean by corrupted ?
How do you know that you have received a full frame of data ?

[biomed12]

This is my settings. I can read all data with labview. This is also my configuring code which get the definitions from gui.

    serial->setPortName(p.name);
    serial->setBaudRate(p.baudRate);
    serial->setDataBits(p.dataBits);
    serial->setFlowControl(p.flowControl);
    serial->setParity(p.parity);
    serial->setStopBits(p.stopBits);

and how can i know if i get full frame of data or not?

[karti gesar]

QByteArray block;
QDataStream out(&block, QIODevice::WriteOnly);
QByteArray q = serial.readAll();
block.append(q);

[jsulm]

@biomed12 Well, it would help more if you would say what the values of baudRate, dataBits, ... actually are.
"and how can i know if i get full frame of data or not?" - this is something you need to specify (define a protocol).

[VRonin]

• serialInData = serial->readAll(); does not read ALL you sent, it just read all that is available at that moment
• use QDataStream

void MySoftware::serialReadData()
{
quint32 receivedNumber;
QDataStream readStream(serial);
for(;;){
readStream.startTransaction();
readStream >> receivedNumber;
if(readStream.commitTransaction())
qDebug() << receivedNumber;
else
break;
}
}

I'm not sure how UARTCharPut handles endianness, QDataStream assumes big-endian byte order

[biomed12]

@jsulm

ok, program side is:

    serial->setBaudRate(QSerialPort::Baud57600);
    serial->setStopBits(QSerialPort::TwoStop);
    serial->setPortName("COM8");
    serial->setDataBits(QSerialPort::Data8);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->setParity(QSerialPort::NoParity);

   serial->setReadBufferSize(4);

device side is:

ROM_UARTConfigSetExpClk(UART6_BASE,systemClock , 57600,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_TWO|
                             UART_CONFIG_PAR_NONE));

...

//uart send function
void UARTSend(uint32_t ui32UARTBase, const uint8_t *pui8Buffer, uint32_t ui32Count)
{
    while(ui32Count--)
    {
        UARTCharPut(ui32UARTBase, *pui8Buffer++);
				
				while(!UARTBusy(ui32UARTBase))
				{
					
				}
	}	
}
...

//the data will be sended
	sendData[0] = 'a';
	sendData[1] = adcValue.bytes[0];
	sendData[2] = (adcValue.bytes[1] & 15);
	sendData[3] = 'b';

//and send the data
UARTSend(UART6_BASE,sendData , 4);

And I created a protocol. Data frame start with 'a' char and stop with 'b' char. So I added a control loop like below, but i get a lot of break frame. So, I discard the value in this situation but, the data is valueable for me. There are much broken frame...

union{
    unsigned char bytes[2];
    unsigned int integerPart;
    unsigned char *ptr;
}serData;

void MedicalSoftware::serialReadData()
{
    QByteArray serialInData;
    //
    serialInData = serial->readAll();
    //
    if(serialInData.length()!= 4 || serialInData[0] != 'a' || serialInData[3] != 'b')
    {
        
        ErrorMessage("missing"); //this is my custom error debugger which shows message
        serial->clear();
        return;
    }

    serData.bytes[0] =(unsigned char)serialInData[1];
    serData.bytes[1] =(unsigned char)serialInData[2];


    if(plotDataButtonStatus == true)
    {
        plotMainGraph(serData.integerPart);
    }
    serData.integerPart = 0;
}

[mostefa]

@biomed12 said in QSerialPort data missing while reading:

@jsulm

ok, program side is:

    serial->setBaudRate(QSerialPort::Baud57600);
    serial->setStopBits(QSerialPort::TwoStop);
    serial->setPortName("COM8");
    serial->setDataBits(QSerialPort::TwoStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->setParity(QSerialPort::NoParity);

device side is:

ROM_UARTConfigSetExpClk(UART6_BASE,systemClock , baud,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_TWO|
                             UART_CONFIG_PAR_NONE));

Is your serialReadData() connected to readyRead signal ?

[mostefa]

@biomed12 said in QSerialPort data missing while reading:

This is my settings. I can read all data with labview. This is also my configuring code which get the definitions from gui.

    serial->setPortName(p.name);
    serial->setBaudRate(p.baudRate);
    serial->setDataBits(p.dataBits);
    serial->setFlowControl(p.flowControl);
    serial->setParity(p.parity);
    serial->setStopBits(p.stopBits);

and how can i know if i get full frame of data or not?

You can add a frame check sequence for example

https://en.wikipedia.org/wiki/Frame_check_sequence

[biomed12]

@mostefa

I am saying that data frame is broken, not data is not coming. İf the situation you say was true, there would not be any data. But I mention, there is frame drifting.

[mrjj]

@biomed12
Hi
Why not check with other serial app and see what coming ?
http://doc.qt.io/qt-5/qtserialport-terminal-example.html
If that works we can conclude its in app code and if it dont
something up with driver or serial port.
Last i would check if anything to do with Qt. :)
Its not very likely unless you compiled it yourself or have a very interesting distro.

[mostefa]

    serial->setBaudRate(QSerialPort::Baud57600);
    serial->setStopBits(QSerialPort::TwoStop);
    serial->setPortName("COM8");
    serial->setDataBits(QSerialPort::TwoStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->setParity(QSerialPort::NoParity);

   serial->setReadBufferSize(4);

device side is:

ROM_UARTConfigSetExpClk(UART6_BASE,systemClock , 57600,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_TWO|
                             UART_CONFIG_PAR_NONE));

In your config ,are you sure about , serial->setDataBits(QSerialPort::TwoStop);?

setDataBits contains an enum and can be

QSerialPort::Data5
5
The number of data bits in each character is 5. It is used for Baudot code. It generally only makes sense with older equipment such as teleprinters.
QSerialPort::Data6
6
The number of data bits in each character is 6. It is rarely used.
QSerialPort::Data7
7
The number of data bits in each character is 7. It is used for true ASCII. It generally only makes sense with older equipment such as teleprinters.
QSerialPort::Data8
8
The number of data bits in each character is 8. It is used for most kinds of data, as this size matches the size of a byte. It is almost universally used in newer applications.

have a look at this enum from qt doc

http://doc.qt.io/qt-5/qserialport.html#DataBits-enum

So for me this should be :

serial->setDataBits(QSerialPort::Data8);

[biomed12]

@mostefa

sorry it was an error while editing the source code. it was like you mention

[mostefa]

@biomed12 said in QSerialPort data missing while reading:

@mostefa

sorry it was an error while editing the source code. it was like you mention

Just for information are you receiving a part of your data ?

Or you do not receive your data at all and receive another insignificant data?

[mrjj]

Hi
Adding to @mostefa , your logic is not optimal ( in serialReadData)
serialInData = serial->readAll(); // this might not read all and next signal will override data already received.
//
if(serialInData.length()!= 4 || serialInData[0] != 'a' || serialInData[3] != 'b')

a more common design is

void MedicalSoftware::serialReadData()
{
//// -> this goes as memeber of class (.h file) QByteArray serialInData;
//
serialInData += serial->readAll(); // we ADD

if ( serialInData.size() >= COUNT_EXPECTED ) { // process
// check format etc
if(serialInData.length()!= 4 || serialInData[0] != 'a' || serialInData[3] != '
serialInData.clear();// clear buffer for next full read. Note if you have excess data u need to handle it here.

[mostefa]

Adding to what @mrjj said

When readall is called you may received just part of your frame,

For example , we are going to send "HELLO WORLD" on the serial port

this can be sent in two times :

at time t0 "HEL" is received
at time t1 "O WORLD" is received

If you are doing your readall, at time t0 you can receive just part of data

To avoid this you can use readyRead signal, and QByteArray buffer

connect(nameOfyourSerialPort,SIGNAL(readyRead(),this,SLOT(onPartOfFrameAvailable());

QByteArray mWholeData;//var member this is our buffer

void onPartOfFrameAvailable()
{
     mWholeData.append(nameOfyourSerialPort->readAll());
     qDebug() << "for the moment wholeData contains" << mWholeData;
}

If you send "HELLO WORLD" the result will be for example:

First output : for the moment wholedata contains "HEL";
Second output : for the moment wholedata contains "HELLO WORL"
Thirs output : for the moment wholedata contains "HELLO WORLD";

[biomed12]

@mostefa
Yes, I have this trouble definitely. I will try and share the results.

[mostefa]

@biomed12 said in QSerialPort data missing while reading:

Yes, I have this trouble definitely. I will try and share the results.

Ok keep us informed ;)

[biomed12]

@mostefa said in QSerialPort data missing while reading:

@biomed12 said in QSerialPort data missing while reading:

Yes, I have this trouble definitely. I will try and share the results.

Ok keep us informed ;)

ooppss.. Qbyte array is getting larger always.

[mostefa]

@biomed12 said in QSerialPort data missing while reading:

@mostefa said in QSerialPort data missing while reading:

@biomed12 said in QSerialPort data missing while reading:

Yes, I have this trouble definitely. I will try and share the results.

Ok keep us informed ;)

ooppss.. Qbyte array is getting larger always.

Getting larger than what?

I don't understand could you provide more details please?