[LinuxPPS] FW: Linux PPS with Garmin 18xLVC using 2.6.35.7 linux Kernel

[Kent Headley]

Thanks for your reply Venu,

The GPS has only RS232 output, which is connected to a Keyspan 19-HS
USB-serial converter.
The Keyspan nominally behaves as a full 9-pin serial port.
For example, statserial can detect changes in the handshaking lines on
/dev/ttyUSB0.

The PPS signal is connected to Keyspan serial pin 1 (DCD).
So both the NMEA and PPS signals are passed to the PC via the Keyspan
(/dev/ttyUSB0).

Is it OK for the NMEA and PPS signals to arrive on the same serial
connector? I have seen this at various sites on the web (PPS wired to DCD),
so figured it¹s OK.
With your uBlox GPS, what pin was the PPS signal attached to?

The comments about sym links for gps0 and gpspps0 are interesting; is that
required by NTP, or does linuxPPS need these links also?

I just tried creating the links you suggested, exactly as you recommend, but
also with

    ln -s /dev/ttyUSB0 /dev/gps0
    ln ­s /dev/ttyUSB0 /dev/gpspps0
instead of
    ln -s /dev/ttyUSB0 /dev/gps0
    ln ­s /dev/ttyS0 /dev/gpspps0

since my PPS is arriving via /dev/ttyUSB0 (on my system, ttyS0 doesn¹t seem
to have an actual UART associated with it).
However, neither of these seems to have the desired effect.

Do you know if any special permissions for /dev/ttyUSB0 (currently
/dev/ttyUSB0 system has ³rw-rw---- root dialout² ).

Thanks again!

Cheers,
Kent

On 10/28/10 1:11 AM, "Venu Gopal" <neo.venu at gmail.com> wrote:

> Hello Kent,
> 
> NTP requires NMEA messages and the PPS signal.
> If I am not wrong, the GPS receiver is connected to the PC via USB
> (/dev/ttyUSB0),
> though which the NMEA messages are read. And how is PPS connected to the PC
> if it doesn't have serial ports ?
> 
> I have used uBlox GPS receiver with both USB and serial connectivity.
> You need to create soft links for NMEA and PPS as shown below:
> 
> 1. For NMEA data:
> ln -s /dev/ttyUSB0 /dev/gps0
> 
> 2. For PPS:
> ln -s /dev/ttyS0 /dev/gpspps0
> 
> You need to have PPS signal reaching to PC either over a serial port or a
> parallel port.
> 
> Regards,
> Venu


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