[time-nuts] NTP/1-PPS/RS232 question

[Mark Sims]

As I mentioned earlier,  the RS-232 interface board that I built is for a non-NTP/non-Time-Nuts project.  But, if I can make it useful in those applications,  great.   I am not going to add any parts to the board for them.  That said,  the MAX3232 chip has an extra RS-232 receiver on it.  I can use it as an inverter and supply either polarity 1PPS signal to the RS-232 connector.  It does add up to 300 nS delay to the 1PPS signal.  I also added a bunch of 0.1" spaced feedthroughs to the board (under where the GPS modules would sit) as a prototyping area.
I tried my application with two of the CN06 receivers.  It  calculates the range and bearing between them.  With the boxes only a couple feet apart,  I was typically calculating 2-5 foot distances with a pretty reliable bearing indication.  That error is at the limit of what single-precision math can deliver (processor is an AVR chip).   Those are pretty slick little GPS receiver modules for 22 bucks...