> I can capture the NMEA data and the TICC data - this is not a problem. > But I'd really like to be able to capture both datasets in some sort of > time-correlated way, so I can easily post-process the TICC data using the > quantization error data. I can probably throw something together in Python > or C to do this, but before I went through the effort, I figured I would ask > if there is a standard tool I haven't been able to find yet which is in > common use.
How accurately do you want to stamp the NMEA data? If the time on your PC is good enough, then software will work. If you can feed a PPS to both the TICC and your PC, then you can get accurate timings on a second signal to the TICC. With a good PPS, ntpd should hold the time on a PC better than a ms. You don't actually need good time on the PC, or a good PPS. All you need is a signal that is ballpark of once a second that you can feed to both the PC and TICC. You can use the PPS capture on the PC to tell you when it arrives without using it to control the time. If you want more accurate timings on the NMEA data, I think you will need to build something to indicate the start of the NMEA data clump and feed that signal to the TICC. The idea is to turn a long burst of transitions into a single pulse so you don't swamp the TICC. [It might just work. I'm assuming the TICC will be overloaded by the NMEA bit stream, but it will probably get the first bit and lots of others. You can throw away the others. Has anybody tried something like this?] You could do it in hardware with a retrigerable one-shot. This assumes that the characters come out back-to-back, no extra time between them due to software being busy doing something else. Set the one-shot for a bit longer than a character time and trigger it from the serial data stream. That will give you an output pulse a bit longer than the NMEA burst. You can feed that to the TICC. If your geek hat is on, you will have to subtract off the delay through the one-shot. (I'm thinking of one-shots because I was working with a FatPPS recently. 74LS123 Thanks John.) If you prefer software, you can do it with your favorite tiny PIC or AVR size chip. That will probably add several cycles of jitter. I'd have to look at the data sheets carefully to work out the details. -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
