From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: RT_PREEMPT with RS232 and USB-RS232 adapter
Date: Wed, 25 Jan 2012 11:56:15 +0100 (CET)
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To: Forconi <forconi@wavecomm.it>
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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?