2008-10-30 16:35:31     gettimeofday changes

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2008-10-30 16:35:31     gettimeofday changes

Servaes Joordens (NETHERLANDS)

Message: 64470   

 

Gentlemen,

 

I frequently call gettimeofday() in my application. The time is relatively accurate in normal usage.

 

However, when I capture an image with my own ppi-driver, the timevalue changes in steps of approx. 4ms.

 

My ppi driver generates an interrupt on every captured line. Then I call a tasklet to do some processing and a copy to RAM.

 

When I do an immediate return in my tasklet the time does not change.

 

Is it possible to influence the time of gettimeofday() by a heavy load tasklet?

 

regards,

Servaes

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2008-10-31 15:18:17     Re: gettimeofday changes

Robin Getz (UNITED STATES)

Message: 64553   

 

Servaes:

 

I think it depends on what the tasklet is doing. If you turn off interrupts - certainly things will be effected.

 

-Robin

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2008-11-12 03:40:03     Re: gettimeofday changes

Servaes Joordens (NETHERLANDS)

Message: 65080   

 

Robin,

 

No I do not turn off interrupts. It is also not a jitter of 4ms, but a cumulative thing. So when running a bit longer I will have a time shift of 1 second.

 

I do call the tasklet frequently. I handle the interrupt after each line of a PPI capture. In the interrupt I schedule the tasklet. So every 30us the tasklet is scheduled.

 

Servaes

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