RetroBSD

2.11BSD operating system for microcontrollers
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Pito
PostPosted: Fri Feb 12, 2016 11:11 am 
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Code:
struct timeval  time_info;
long tstart, tstop, elapsed;
long micros(){
   gettimeofday(&time_info, 0);
   return (time_info.tv_sec * 1000000L + time_info.tv_usec);
}


Why the time_info.tv_usec resolution is 10ms in RetroBSD, SmallerC?
Cannot be made better?

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Pito
PostPosted: Sat Feb 13, 2016 12:13 am 
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Precise interval measurement - maybe we shall run a 32bit hw timer, fed by 1MHz or something like that, and read via a syscall (micros()). That allows for 72minutes at 1us resolution.

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wiz
PostPosted: Sat Feb 13, 2016 8:06 pm 
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Hi Pito,

I just read the CPU counter directly. Store that and do the math later. I suppose an interrupt routine could extend the counter to whatever number of digits makes sense for applications needing longer intervals.

Lots of fun :).

Wiz
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Pito
PostPosted: Sun Feb 14, 2016 10:42 am 
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You cannot read cpu tick timer directly.. Moreover it runs over in 107secs.

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wiz
PostPosted: Sun Feb 14, 2016 8:58 pm 
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Hi Pito,

IIRC I did it with a syscall.

Wiz
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vak
PostPosted: Fri Feb 19, 2016 6:50 am 
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Pito wrote:
Why the time_info.tv_usec resolution is 10ms in RetroBSD, SmallerC?
Cannot be made better?

This problem has been solved in LiteBSD. A special machine-dependent routine microtime() is used to obtain a time value with microsecond precision. It should be pretty easy to back-port to RetroBSD kernel as well.
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Pito
PostPosted: Tue Feb 23, 2016 8:13 am 
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The retrobsd community would be happy if you may put that on your todo list, plz :)

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Sumland
PostPosted: Mon Nov 20, 2017 2:54 pm 

Joined: Thu Nov 09, 2017 11:52 am
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Has this issue been resolved? I remember I've had the same problem, but I stopped using the software soon after.
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