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fabs.rodriguez 看全部
2019-7-4 14:55:52
Edited by fabs.rodriguez at 2019-7-4 15:10

Hi. I've got an Orange Pi Zero, and I have a few questions regarding the clock on it, which I'd appreciate any help with.I am running the latest Armbian Stretch (4.19.y) and have the latest version of Mono installed, running a .Net 4.7.2 console app that I wrote.

In Mono, when I request the time (DateTime.Now in C#) I notice two things:
1. The date/time is correct - barring the time zone error (2 hours here in South Africa).
2. it gives me up to millisecond resolution.

I have three questions regarding this:

1. Since I did not set up the date/time, and I don't have a Real Time Clock installed on the board, I can only assume Armbian automatically grabs the date/time from some time server when it has an internet connection. Is this assumption correct?
2. Is the only purpose of a Real Time Clock to keep the date/time correct, when the board is powered off, and no internet is available? Does it offer any other advatnages, like better timing accuracy or resolution? (I have a Maxim DS1307 RTC that I'm not currently using, but am considering maybe using)
3. What is the accuracy of the Orange Pi Zero's clock? Like I said, when I execute DateTime.Now in C# / Mono, I get up to millisecond resolution. How accurate is this? Is it truly accurate to 1 millisecond?

Thank you


hal8000b 看全部
2021-1-14 02:18:24
Hi, to answer your questions:



1. Since I did not set up the date/time, and I don't have a Real Time Clock installed on the board, I can only assume Armbian automatically grabs the date/time from some time server when it has an internet connection. Is this assumption correct?

When you boot your OrangePi the correct  date/time is taken from a Network server so  time at boot will  be accurate


2. Is the only purpose of a Real Time Clock to keep the date/time correct, when the board is powered off, and no internet is available? Does it offer any other advatnages, like better timing accuracy or resolution? (I have a Maxim DS1307 RTC that I'm not currently using, but am considering maybe using)

Yes, if the board is powered off  and no network then a RTC will maintain the time.


3. What is the accuracy of the Orange Pi Zero's clock? Like I said, when I execute DateTime.Now in C# / Mono, I get up to millisecond resolution. How accurate is this? Is it truly accurate to 1 millisecond?


Remeber that your Orange Pi is a computer not microcontroller so its running many con-current tasks.
Many people will tell you thatt Linux is not real  time but  so what? How many real time systems do you work with?
If youre going to control hardware from the GPIO  ports like relays then this question is academic as it takes 30 or 50ms for a relay
to respond.
The Orange Pi is probably not truly accurate to  1 ms   but you can  eitehr call the NTP time server to update time,

use a real time clock or perhaps interface to a microcontroller.

I cannot think of any program or device that requires accuracy of  a millisecond, so may help if you explain what
hardware you are trying to control.

Hope that helps.



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