[ntp:questions] What is the NTP recovery time from 16s step in GPS server?

David Taylor david-taylor at blueyonder.co.uk.invalid
Wed Oct 31 18:29:15 UTC 2012

On 31/10/2012 17:22, Rob wrote:
> I see errors that are related to permission.

I had wondered about that as well...

> I would recommend to type in the session before you do anything else:
> sudo sh
> or: sudo bash

OK, I can try that.

> When it works ok you should have a shell running as root, and then
> you can stop the service and start gpsd without the risk that you
> start to run it as user 1000 (which appears to be happening according
> to the logs), and this user probably is not allowed to use the serial
> port.
> There are various things you could do to allow serial port access for
> the user, but it should not be required as gpsd normally starts as
> root to open the port and then changes to user nobody for its server
> activities.
> Is /dev/ttyACM0 the name for the USB serial port?  Is there a
> /dev/ttyUSB0?  Maybe you could try that.
> Using USB ports in a service started at boot time should normally
> work ok, but when it has issues on the Raspberry maybe it could
> be solved by delaying the startup of gpsd a bit.  But don't try to
> tackle all issues at the same time.
> The log output of the Time with offset 16 is OK.  What does it
> show when you powercycle the receiver?

I appreciate you taking the time to comment, Rob.

Ignoring the offset for the moment, if I power up the Rasberry Pi from 
cold while it sees the PPS signals (to an interrupt-driver GPIO pin) is 
never sees gpsd data ( and trying cgps -s also times out with a can't 
connect).  I've left it for about 30 minutes but gpsd never sees data. 
When I then do a warm reboot NTP sees data from gpsd right away and cgps 
-s works as well.

My feeling is that I should concentrate on getting the PC to see GPS 
cold from a cold boot first, and then worry about any 16-second step. 
Would you not agree?  If so, what magic file to I have to edit and how 
to delay gpsd starting?

Actually, I'm not even sure myself, as I recall that from a cold boot, 
stopping and restarting gpsd isn't enough to start the data flow, the 
GPS receiver itself has to be plugged out and back in, but I'm happy to 
try a delayed gpsd start.

What do you think?
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