From: Wolfgang Grandegger <wg@grandegger.com>
To: Mohamed HAMZAOUI <requinham@gmail.com>
Cc: Linux-CAN <linux-can@vger.kernel.org>
Subject: Re: [SocketCan] Problem of accuracy
Date: Mon, 09 Jul 2012 14:15:44 +0200 [thread overview]
Message-ID: <4FFACB70.7020202@grandegger.com> (raw)
In-Reply-To: <CABMxt4iYNuvN14_OtTQHdcMWNs0+KaAE0PqTBCQkT6tFN=NGsQ@mail.gmail.com>
On 07/09/2012 01:57 PM, Mohamed HAMZAOUI wrote:
> If i have understood you correctly, I think it must change the period
> if the write function is a synchronous call !
> if my function is like this :
>
> while(1)
> {
> nannosleep(1000000);
> write (myFrame in opened CAN socket);
> }
>
> then the result is 1ms + timeOf (write) for every iteration.
Yep.
> but if the write call is asynchronous we return to case you mentioned !
The write call is asynchronous and I'm surprised that it takes 300us to
return. Could you show us your test program?
> Is this correct ?
Anyway, in a previous mail you wrote:
> i use clock_nanosleep with (1000000 ns = 1ms) and the result mesured
> with another CAN transeiver is an average of 1.30 ms (delta = 300 µs)
> !
You cannot expect precises timing with nanosloeep(). Have a look to
cyclictest.c to understand how to implement a periodic task.
Wolfgang.
next prev parent reply other threads:[~2012-07-09 12:15 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CABMxt4ijuTMYFYXx0n4AYBO6-=SRD0U3F4BTA2=rWE80Z4-yOA@mail.gmail.com>
2012-07-05 8:38 ` Problem of accuracy Oliver Hartkopp
2012-07-07 10:02 ` [SocketCan] " Mohamed HAMZAOUI
2012-07-07 10:32 ` Wolfgang Grandegger
2012-07-08 19:43 ` Mohamed HAMZAOUI
2012-07-08 20:13 ` Wolfgang Grandegger
2012-07-08 20:30 ` Mohamed HAMZAOUI
2012-07-09 7:18 ` Wolfgang Grandegger
2012-07-09 8:14 ` Mohamed HAMZAOUI
2012-07-09 8:20 ` Wolfgang Grandegger
2012-07-09 9:19 ` Mohamed HAMZAOUI
2012-07-09 9:22 ` Wolfgang Grandegger
[not found] ` <CABMxt4jnztXqAmLFcBnqp3001QXds1nX3xA2y_ka=xCNr0cjjA@mail.gmail.com>
[not found] ` <4FFAB09F.6090800@grandegger.com>
[not found] ` <CABMxt4jLRKz8xKNbH3Qa=P0k1aEjMsqmo2vArGDo2O1Wf0=wGQ@mail.gmail.com>
2012-07-09 11:26 ` Fwd: " Mohamed HAMZAOUI
2012-07-09 11:40 ` Wolfgang Grandegger
2012-07-09 11:57 ` Mohamed HAMZAOUI
2012-07-09 12:15 ` Wolfgang Grandegger [this message]
2012-07-09 13:19 ` Pavel Pisa
2012-07-09 14:29 ` Mohamed HAMZAOUI
2012-07-09 14:35 ` Mohamed HAMZAOUI
2012-07-09 14:40 ` Kurt Van Dijck
2012-07-09 14:57 ` Alexander Stein
2012-07-09 15:39 ` Mohamed HAMZAOUI
2012-07-09 17:08 ` Oliver Hartkopp
2012-07-09 20:50 ` Wolfgang Grandegger
2012-07-10 22:11 ` Mohamed HAMZAOUI
2012-07-11 12:35 ` Mohamed HAMZAOUI
2012-07-11 22:22 ` Wolfgang Grandegger
2012-07-11 22:19 ` Wolfgang Grandegger
2012-07-09 6:55 ` Kurt Van Dijck
[not found] ` <1341488146.2416.9.camel@slaptop>
2012-07-05 13:57 ` [Socketcan-users] back to back can frames Kurt Van Dijck
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