check SerialPort successfully written to

Aeroplane123

I have a program where I am writing to a serial port, if the write was a success I want bool to return true or false.

When this line runs...

bool success = serialPort.write(someData);
qDebug() << success;

I get the debug output "true". The serial port is not even connected!, please can somebody explain why it returns true when the serial port is not open....

QIODevice::read (QSerialPort): device not open

jsulm

@Aeroplane123 said in check SerialPort successfully written to:

QIODevice::read (QSerialPort): device not open

Here you are trying to read from serial port: is it the same QSerialPort instance as the one you're using for writing?
https://doc.qt.io/qt-6/qiodevice.html#write returns number of bytes written, not a boolean. In case it fails it returns -1 (which converts to TRUE if you assign it to a boolean!), so you should check the return value properly.

Aeroplane123

Ah yes sorry, yes the serial port is definitely not open when I try to write. Yes it the same instance.

so I want to do

serialPort.write(someData);

But then please how can I check if it did actually send via the port?

jsulm

@Aeroplane123 said in check SerialPort successfully written to:

But then please how can I check if it did actually send via the port?

Basic C/C++ stuff:

bool success = serialPort.write(someData) != -1;

Aeroplane123

serialPort.write(someData);

bool success = serialPort.write(someData) != -1;

qDebug() << success;

output is "True", but thre is no port open.

JonB

@Aeroplane123
Please just try qDebug() << serialPort.write(someData);.

Aeroplane123

OK, oddly now it is giving me false and -1, which is what I expect.