Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

2017-02-17 Thread Bob Camp
Hi Roughly speaking, if you have a 10 MHz clock driving a timer and the pin latches data from that timer, you get 100 ns “buckets and +/- 100 ns “jitter”. You can find MCU’s that will do this for < $1. If you go crazy, you can spend < $10 and still get a very fancy MCU on a board with all

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

2017-02-17 Thread Christopher Hoover
> > The Intel guys have some *very* fast timers flying around their cpu’s. > They would laugh > at the idea of a 10 or 100 MHz clock. If you can configure the pin to grab > the data off those timer, you > have way better than 100 ns at the timer. We're most certainly getting off topic, but the

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

2017-02-17 Thread David
On Tue, 14 Feb 2017 10:31:30 -0500, you wrote: >On 14/02/2017 7:26 AM, Bob Camp wrote: > >> A direct port might be a +/- 100 ns sort of thing most of the time and a >> +/-10 us >> thing every so often under some OS’s. Most desktop operating systems are not >> designed to prioritize random pin