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Re: Adafruit USB and PPS

From: Gary E. Miller
Subject: Re: Adafruit USB and PPS
Date: Tue, 3 Dec 2019 13:50:17 -0800

Yo Neal!

On Tue, 3 Dec 2019 06:03:45 +0000
Neal Dillman <address@hidden> wrote:

> With a lack of any suggestions today I took a look at the cp210x
> driver.  It appears to have RI support, and also appears to have had
> changes over the last couple of years, so I decided to update
> everything to the latest version (apt update; apt full-upgrade).
> While the upgrade was successful, it has had no effect on PPS
> working. :(

Not would I have expected it to.

The way to tell if the driver is working is to simply run the ppcheck
program from gpsd.  All as root (no sudo).

Be sure gpsd is not running:
        pstree -paul | fgrep gpsd

Then run ppscheck against your serial port:
        ppscheck /dev/ttyUSB0

 1575409559.092768291 TIOCM_RI TIOCM_DSR
 1575409559.092828852 TIOCM_RI TIOCM_DSR TIOCM_CTS
 1575409559.092847948 TIOCM_RI TIOCM_DSR

You can clearly see the CTS line toggling.

If any of them are toggling, then your are good.

> Is there anything needed to tell PPS to use RI as opposed to DCD?  It
> appears not, but I thought I had best ask just in case.

No need.  From ppsthread.c, line 455:


You can see that gpsd looks at CD, RI, CTS and DSR all at the same time.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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