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Visitor
Visitor
3,370 Views
Registered: ‎10-31-2012

Time in ZedBoard.. using the date function

All,

 

I am trying to set the time and date on the ZedBoard. I notice that the time keeps drifting on the ZedBoard when compared to the real-world time i.e if I check the date and time using the "date" function at say 8.30am,real world time it gives me an accurate reading but when I measure time at 8.45am,real world time, the time has drifted away by more than 15 minutes and I get wrong values

 

Is there any config file I have to modify to overcome this? Or is there no support on the ZedBoard for this purpose?

 

Thanks

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Xilinx Employee
Xilinx Employee
3,358 Views
Registered: ‎03-13-2012

In general this should work and you shouldn't see such a huge drift. The devil may be in the details though:

 

The main time source on Zynq is the TTC whose frequency is derived from the CPU clocks.

 - depending on the kernel version you use you might have to adjust the timer frequency in the DT in case you run the CPU at a custom speed

 - Usage of CPU frequency scaling might be problematic. Though it should work w/o messing up timing.

 

On the current kernel these things shouldn't be a problem though.

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Visitor
Visitor
3,343 Views
Registered: ‎10-31-2012

Will I not face this issue if I run the latest version of the Zynq release (14.7)?

 

I am facing this issue and I do not want to run the CPU at custom frequencies. I just want the ZedBoard clock to be synchronized to the real world clock

 

Thanks

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Xilinx Employee
Xilinx Employee
3,330 Views
Registered: ‎03-13-2012

Well, to have proper day/time support - even over reboots - the system needs a real time clock. I don't know whether the Zedboard has one or not.

Other than that, once set, Zynq should be able to maintain the time correctly, within the accuracy of timers and oscillators used on your board. That will certainly not be perfect, but you shouldn't see a 15 minute drift on a 15 minute interval.

I'm not aware of any significant changes to the timer drivers or similar that would affect this behavior, but just try if the update helps.

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