[time-nuts] Serial or other simple protocols for exchanging time

[Hal Murray]

ausserirdischesindgesund at gmail.com said:
> I am a newbie and am wondering what options there are for exchanging time
> on a more basic level than NTP or PTP (that is for situations when a
> full network stack is too complex). 

You haven't described your problem fully yet.

Are you interested in client side or server side?  (or both)

What sort of environment are you working in?  What sort of hardware do you 
have available?

NMEA over a serial port is probably what you want, but...


Raspberry Pi and similar are not very expensive.  They come with networking 
software.  The Pi isn't very nice for time-nut work over the net because the 
Ethernet is on USB which adds jitter and/or hanging bridges.  It does have 
GPIO.


There is a lot of things you can do without a "full network stack".

What level of hacking is reasonable depends on your environment.  For a setup 
at home, you are unlikely to annoy anybody else.

The Alto firmware could boot over the (3 MB) Ethernet.  The boot servers would 
periodically send a boot-loader packet to a reserved hardware address.  The 
firmware only had to setup the hardware to receive a packet, wait for one, 
sanity check things, and jump to it.

If you use UDP rather than TCP, the "stack" level packet format is much 
simpler.  Retransmission becomes trivial if you only have one un-ACKed packet 
to consider.  Performance on a LAN is OK most of the time.

For something like a NTP server, you can avoid routing and ARP by sending the 
reply back where it came from.

For the client side, the normal problem is finding the server.  If you only 
have one server, you can wire in the address.




-- 
These are my opinions.  I hate spam.