"David Lord" <> wrote in message news:[email protected]... [] > The pps via usb doesn't work with NetBSD. That is I believe lack > of hardware interrupt capability via usb. Possibly latest > development pps might work from usb on Linux.
It certainly works on Windows. Is that because Windows does a better job of emulating the interrupts than NetBSD does, or because of the architecture which Dave Hart developed for Windows does a better job of picking up the timing, or because I was lucky with my USB device or its drivers? > Problem I'm seeing is good ttl inputs (< +300mV) to usb converter > not producing any output at pc whilst > > (1) ok using modem connected to serial input of converters. AT > commands via cu work ok. > > (2) some erratic recogniable output with ttl input to converter > (PL2303), no output with ttl input to converter (FTDI). > > (3) ttl outputs connected to serial inputs on server work ok > from gps18x-lvc+pps (2us) > > (4) ttl outputs possibly a bit erratic for pps from Conrad MSF > module via diy pps extractor as only 25% of polls with reach 377, > but possibly this is to be expected. MSF via dsr or dcd almost > 100% reach 377. Agreed it sounds like levels. > So usb to pc is ok and it does appears my ttl levels at converter > inputs aren't acceptable. I expect output +9v to -9V via a 1488 > will be ok. I've not set that up yet as intended generating > +/-10V using switched capacitor converters I ordered, but these > didn't arrive and went from "in stock" to "no longer available" > overnight between my order being accepted and delivery of > remainder of order. I'll try this week with 1488 on +/-5V and > higher from bench psu. Tiresome about the chips! [] > Gerhard Dangl's astronomy equipment > <http://www.dangl.at/ausruest/gps18lvc_e.htm> Fascinating page..... > above page shows scope traces -5V to +5V swings from gps18x-lvc. > Spec states 0V to +5V and data sheet I have is same as latest on > Garmin site. > > I have pico and velleman pc scopes but rarely use them. I might > try capturing some waveforms from my kit. If the Garmin can deliver +/-5V, it should certainly drive almost any reasonable RS-232 port. It sounds as if your USB converter has a lower input resistance than the Garmin is expecting, or has too high a hysteresis. I can't recall offhand what the specification is for RS-232 - a few K-ohms is what I recall. If you want to see inside the older GPS 18 LVC: http://geoff36.googlepages.com/insidegarmin18lvcgps Cheers, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
