Re: [Gumstix-users] Need to change linux interrupt (jiffy) from 100hz to 1000hz using OE

[Ned F. <nfo...@wh...>]

On 10/22/2009 04:18 AM, Timo Birnschein wrote:
> 
> Hi Joemoore,
> 
> I'm currently having the same problem with my Verdex 6 pro. Since you
> mentioned you know a way to set the tick frequency to 1000Hz using buildroot
> I'd like to ask for the way to do that  :) 
> I did some google search on the topic but didn't find any way to configure
> the CONFIG_HZ=1000 using buildroot. Do you still know how to do that?
> 
> With best regards,
> Timo
> 
> 
> 
> joemoore wrote:
>>
>> Hi,
>>
>> I'm using a verdex motherboard and I need change my linux interrupt
>> frequency from 100hz to 1000hz in order to speed up my data transfer.  I
>> believe the current 100hz interrupt setting is limiting the speed of my
>> serial communication from my microcontroller to my gumstix to 100hz, even
>> though the baudrate is 115200, and therefore should be able to transfer a
>> single byte faster than 100hz.  I know there is a way to do this in
>> buildroot, but I'm currently using open embedded on my processor.  I also
>> know this question has been asked on the forum previously regarding OE,
>> but it has yet to be answered.  What files need to be changed in
>> open-embedded so that when I rebuild the kernel, it will allow linux
>> interrupts to run at 1000hz?

I don't know how to do this for OE and another poster has already given
directions for buildroot, which look correct on a quick read (I have
changed this value in my own old buildroot project).

Note however that the CONFIG_HZ value has nothing to do with interrupt
latency; responses to interrupts occur when interrupts arrive.  What the
value controls is the frequency with which the scheduler re-schedules
non-interrupt tasks.  If you are having trouble sending serial data at
speed, you must have constructed your code to send few characters at a
time, then somehow to sleep until the next schedule time.

-- 
Ned Forrester                                       nfo...@wh...
Oceanographic Systems Lab                                  508-289-2226
Applied Ocean Physics and Engineering Dept.
Woods Hole Oceanographic Institution          Woods Hole, MA 02543, USA
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