Re: [ts-7000] high resolution timers and real time

[Walter Marvin <>]

Nonsense

Linux handles real time quite well. Mark simply does not know how to do it properly

Walter

---

From: Mark Featherston <>
To:
Sent: Monday, April 9, 2012 1:53 PM
Subject: Re: [ts-7000] high resolution timers and real time

 

Komal,

I would not recommend going down the route of using kernel patches for high resolution timers in Linux for controlling a motor.  Linux is not well suited for hard realtime applications.  However, the FPGA on our boards is very good at meeting very specific timing like this.  We have created FPGA cores on the TS-7558-BOX and TS-7520-BOX with a common software interface which includes PWM control.  I would recommend migrating to one of these boards which can then use a very simple example:

http://www.embeddedarm.com//wiki/index.php/Daqctl#Controlling_a_Servo

http://www.embeddedarm.com/products/board-detail.php?product=TS-7520-BOX

http://www.embeddedarm.com/products/board-detail.php?product=TS-7558-BOX

Best Regards, 

________________________________________________________________

 Mark Featherston, Technologic Systems | voice: (480) 837-5200

 16525 East Laser Drive                | fax: (480) 837-5300

 Fountain Hills, AZ 85268              | web: www.embeddedARM.com 

On Apr 2, 2012, at 12:39 AM, komal wrote:

 

Dear Sir,

I have recently acquired a ts-7500 board with the development kit. The SD card comes with a 2.6.24 Linux Kernel. After a few days of experimenting I have realized that my application (controlling a servo through PWM) will require HRT and RT support which the Kernel is unable to provide (maximum timer resolution I am getting on the current Kernel is 20ms).

I am new to Linux and embedded systems development and hence I am a little confused about how to tackle this problem. I do not understand what you mean by applying the patches and how to apply the patch. Can i simply do it on-board my board with the SD-Card. I have a windows PC with Eclipse for Development.

Any help you can provide me will be highly appreciated. Thank you.

Regards,
Komal RAUF

--- In , Peter Gammie <> wrote:
>
> Charles, any anyone interested in hrtimers:
>
> With Andrew's help I managed to build a 2.6.32.3 kernel that seems to work. Attached are a config and a patch, based on this:
>
> http://lkml.org/lkml/2009/7/22/119
>
> that enable hrtimers. I've lightly tested it on a ts7260 with 64Mb of memory. I loaded the kernel via TFTP with:
>
> load -r -b 0x00218000 -h 192.168.1.1 z
> exec -c "console=ttyAM0,115200 ip=192.168.1.50:192.168.1.1:192.168.1.1:255.255.255.0:ts7200a:eth0:off root=/dev/mtdblock1"
>
> (i.e. no special memory options or anything.)
>
> So the routine is to apply Matthieu's patches, then this one. I expect it will apply to other kernel versions (specifically 2.6.29.6 if you want -RT) without too much bother - but be careful that the Kconfig patch applies to the right system type!
>
> As for the clock multiplexing, Charles's suggestion of using just a PREEMPT (not RT) kernel results in better behaviour under light periodic load (it doesn't flicker while running top on the console) but about the same under heavier load (scp'ing a few megabytes via ethernet). I have the CONFIG_NO_HZ (tickless) option set, which may or may not do anything in particular...
>
> So, more investigation is required.
>
> Thanks for all your help.
>
> cheers
> peter
>
>
>
>
> --
> http://peteg.org/
>

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