UI text to char

[anda_skoa]

You are doing a double conversion there, potentially lossy.

First you encode the QString returned by toPlainText() with the 8-bit codec used for local encoding (toLocal8Bit()), then you convert back to QString using UTF-8 (when assigning to the QString variable).

If your low-level API required a char*, then first get the encoded form as a QByteArray and then send its constData().

E.g.

const QByteArray data =  ui->MotorCommandText->toPlainText().toLocal8Bit();
low_level_write(data.constData(), data.size());

const QByteArray data =  ui->MotorCommandText->toPlainText().toLocal8Bit();
low_level_write(data.constData(), data.size());

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Cheers,
_