Hi all - not sure if this is 8051 related (but I am implementing it on an 8051) so feel free to move this thread as appropriate.

I am developing on the Silabs C8051f040 with CAN, I have the CAN working fine.

as part of my application I am wanting to have a global time stamp for some of the events on the bus, ie all devices have a common timebase.


I also want to track the uptime of the device. - this is easy

struct uptime {
	unsigned int mSecs;
	unsigned char secs;
	unsigned char mins;
	unsigned char hours;
	unsigned int days;
}; 

The question really is, how do you keep track of a common time base across all devices?

My initial thoughts were that's easy, when a new device comes online simply have it broadcast a "reset your clock to 0" message and then all units are back in sync. While this works fine, it means that if I am storing times in a database (I haven't done this yet) then the times will appear to randomly reset back to 0 each time a new device is connected to the bus.

Alternatively, I could listen for devices coming online and have the first device online broadcast the current (or a current) time, that all devices then re-sync to. This to has issues, what if this device fails, who becomes time keeper?

How have any others approached this??

Thanks and regards

Marshall Brown