[time-nuts] An embedded NTP server

Jim Lux jimlux at earthlink.net
Thu Jan 3 02:26:24 UTC 2013


On 1/2/13 5:34 PM, Tom Harris wrote:
> +1 for Forth!
>
> +1 for your opinions on PICs & AVRs. We can buy low end NXP ARM Cortex M0
> chips (e.g. LPC1113) for less than the PIC18 we were using before, and it
> has a real compiler and (unlike the real world) evidence of intelligent
> design!
>
> Do you really need an OS? Surely for a box that is only ever going to be an
> NTP server you just need a network interface and good maths? I've just seen
> a later comment where you mention floating point support, but would 64 bit
> integer maths work just as well?


Well, one might not need a full-up multitasking OS, but I'd sure like to 
have a high level interface to the network (say BSD sockets or something 
like that).  And most OSes (or OS-like infrastructure) also gives you 
some handy stuff like timers, threads, queues, etc.

If you are doing something that is TRULY single function, the "one big 
loop" scheme can work, particularly if you've got a lot of nice 
libraries to do stuff like string handling/parsing/device interaction.

I think the dividing line might be where you are trying to do more than 
one thing with different time scales. It would be straightforward to do 
something like multiple PID loops with a common sample/update rate (like 
a lot of PLC industrial controllers do), but as soon as you start 
running things at different rates (check the Ethernet, check the serial 
port, update the loop, etc.)  having an OS to do the book-keeping is 
pretty nice.







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