On Tue, 18 Mar 2008, marcolamonato wrote:
> Hi,
>
> I've got a TS-7250 with RTC installed
>
> 1) can I print the machine clock time with the micro-second
> resolution?
>
> 2) how?
>
> So far, I've only been able to have a 10-usec resolution, with the
> following C code:
>
> /* Variables */
> time_t actual_date;
> struct tm *actual_time_tm;
> struct timeval tp;
> long milli;
>
> /* Time Print */
> actual_date = time(NULL);
> actual_time_tm = gmtime(&actual_date);
> gettimeofday(&tp,(struct timezone *)NULL);
> milli=tp.tv_usec/1000;/* For 3 digit resolution */
> printf("\nTime: %02d:%02d:%02d.%03d\n", actual_time_tm->tm_hour,
> actual_time_tm->tm_min, actual_time_tm->tm_sec, milli);
>
>
> This prints out something like:
> "Time: 09:06:05.770"
> "Time: 09:06:05.780"
> "Time: 09:06:05.850"
>
I think you mean 10millisec resolution!
Actually you are not printing out the time form the RTC.
On boot the linux kernel reads the RTC, or queries an NTP server, or uses
rdate or similar, to set the system time. By arranging the hardware to give a
tick and with quite a complicated tick adjust system, the kernel keeps time
while running.
The "tick" is traditionally, 2.4 kernel, configured when the kenrel is
compiled to 100Hz. You can rebuild a kernel with a more accurate tick,
but it up the kernel load - the tick is used by the kernel for scheduling etc.
There is a spare timer counter on the 9302 that's available for use - you'd
have to write a kernel driver for it. There is an example kernel driver by
Phillip McCarley, that uses the timer/counter to do faster sampling with the
MAX197 ADC. It is in the file area of the group. Look for ADC kernel driver.
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