Re: RT_PREEMPT with RS232 and USB-RS232 adapter

On Thu, 19 Jan 2012, Forconi wrote:

I'm working on an RT_PREEMPT patched kernel to test a small C
program that sends 39B of data on the serial line every 50ms.

I'm testing the timing accuracy using a scope on the TX pin of the
serial cable.

When I run the application using /dev/ttyS0 as serial port I see
data starting every 50ms, but when I run the application using a
Prolific PL2303 USB-RS232 adapter on /dev/ttyUSB0 I see data out
every 250ms.

Is this possible or I'm doing something wrong?

Why do you expect that USB is in any way deterministic?