recieving Frame of 8 bytes in QT Creator GUI via serial port - c++

Question

I'm working to send frame of 8 bytes to Micro-controller Xmega128a1 (via RS232) the frame looks like this
{header1,header2,CMD,D1,D2,D3,D4,CRC},
for example
{0x55,0xaa,0xFF,0x59,0xfd,0x64,0x68,0x32},
Micro-controller has to resend the frame back to PC, if it's 'correct'.
I built GUI in QT Creator I defined the Headers (header0=0x55, header1=0xaa) and CMD=01 also calculated the CRC,
the user has to enter the data field in the Line_Edit which is value in RPM(Real value) The Micro-controller Receive the frame byte byte and resend the full frame, so I have to send the frame in the form of bytes, when I send the frame I receive the headers, command and CRC correctly, but data field Received not in proper way such in the picture below, my problem is with converting the input value in the Line_Edit to bytes to be send inside the frame, when I tried to send the value 1265 RPM I received the frame {55aa0100209e44fb} but I want to receive the frame look like this {55aa014F109e44fb}, where: (1265)DC=(4F1)HEX, I couldn't figure what's the problem with my code:
the way I read data from serial port:
void MainWindow::read()
{
uint64_t size = serial->bytesAvailable();
if (size > 0)
{
QByteArray data;
data.append(serial->readAll());
ui->termial_textEdit->append(data.toHex());
}
}
the send value in RPM code:
#define CMD_SPEED_REF2 0x01
void MainWindow::on_speed_ref2_lineEdit_returnPressed()
{
uint8_t frame2[8];
frame2[0] = 0x55;
frame2[1] = 0xAA;
frame2[2] = CMD_SPEED_REF2;
float fdata2 = 0.0f;
fdata2 = ui->speed_ref2_lineEdit->text().toFloat();
uint8_t *data2 = new uint8_t();
data2 = (uint8_t*)&fdata2;
frame2[3] = data2[0];
frame2[4] = data2[1];
frame2[5] = data2[2];
frame2[6] = data2[3];
frame2[7] = frame2[2] ^ frame2[3] ^ frame2[4] ^ frame2[5] ^ frame2[6];
serial->write((char*)frame2, 8);
}
this Image Illustrate what happens:recived frame

Answer 1

I think your code mostly looks ok. The one area that looks very suspect is your conversion of the text/string back into binary.
Since you convert your binary into a string with:
ui->termial_textEdit->append(data.toHex());
You should in theory be able to use the following to convert it back:
// Convert back...
QByteArray binaryData = QByteArray::fromHex(ui->speed_ref2_lineEdit->text().toLatin1());
// Print to debug to check it...
qDebug("d1: %02x, d2: %02x...etc...\n", binaryData[0], binaryData[1]);
// or just
qDebug() << "data:" << binaryData.toHex() << endl;
Not on my qt PC until Monday so I can't verify this code, so there may be a bug in there somewhere... I'll check it on Monday!
For serial comms I always use QByteArray's instead of char/uint8_t arrays (when using Qt) because they are so easy to use. You can re-build your array like this:
QByteArray frame2;
frame2.append((char) 0x55); // not sure you need to cast it here
frame2.append((char) 0xAA);
frame2.append((char) CMD_SPEED_REF2);
:
etc
:
If you MUST send as a char * then just do:
serial->write(frame2.data(), 8);
//or
serial->write(frame2.data(), frame2.size()); // if you want to send the whole thing