...

What would you get? Just wondering if the problem is at the tty driver (which probably hasn't changed in eons) , whatever mass-storage device driver that you're dumping data to or something else in the kernel.

The driver module for the USB converter (usbserial) attached itself to ttyUSB0 and it works very well, so I am inclined to think that tty not an issue here.

...

While the program is running, take a peek at /proc/interrupts too.

yep! I could see UART activity on IRQ4.

I'm about to leave work for the weekend, but you should use termios to make sure that you set the serial port to use flow control.

Hope you had a good week end! I did indeed use termios (My book told me too) although not dead sure it was activated. You suggested getting the oscilloscope out... err, maybe another time.

If your program uses hardware flow control and the device uses hardware flow control, you should not have any buffer overrun problems.

Since using USB converter, the data upload takes 30seconds, i.e. 2 more seconds than before with the same baudrate and the same port configuration. How do you explain that??? USB is not the weakest link since it is natively faster than legacy serial. So, the explanation is perhaps that the uploads breaks and resumes, indicating that hardware flow control is now in place. Another question: I read on the Agilent website that Microsoft never implemented a true hardware flow control for the UART with Windows, but instead used another software layer to virtualise the control of flow signals. The reason apparently was that, when windows 3.1 came out, they could not unify all UARTs variants given that they all behaved a bit differently with respect to flow control signals. But, even though PC hardware is now a lot more uinified, they have kept this way of handling flow control. Is this right? I presume this is not the case with Linux? ------------------------------------------------------------------- This e-mail and any attachments may contain confidential and/or privileged material; it is for the intended addressee(s) only. If you are not a named addressee, you must not use, retain or disclose such information. NPL Management Ltd cannot guarantee that the e-mail or any attachments are free from viruses. NPL Management Ltd. Registered in England and Wales. No: 2937881 Registered Office: Serco House, 16 Bartley Wood Business Park, Hook, Hampshire, United Kingdom RG27 9UY -------------------------------------------------------------------