Re: [gpsd-users] NTP1 keeps going away.

[Alexander Carver]

On 2017-11-09 11:34, Gary E. Miller wrote:
> Yo Alexander!
> 
> On Thu, 9 Nov 2017 10:58:38 -0800
> Alexander Carver <address@hidden> wrote:
> 
>>> One other thing that is a common problem.  Do you know the voltage
>>> on your PPS pin is compatible with your pps input?  I'd like to see
>>> your PPS output at almost swing zero to five volts.  
>>
>> So you'd like to see his Raspberry Pi burned out, then.  The Pi has a
>> 3.3 VDC input limit on GPIO pins.
> 
> 
> Ah, thanks, I forgot he was on a RasPi.  So it should be 3.3V logic.
> 
> Maybe his problem is he used 5V and did burn out a pin?
> 

Now that is indeed a possibility.  He talked about a "PPS to GPIO cable"
in his first post which suggests, to me, that he's not using a Pi Hat
but some external GPS with the PPS signal routed to GPIO. A Hat with
integrated GPS would have already had voltage limiters and level
shifters  to prevent damage.  Many external GPS boards are 5V devices so
if he wired directly then that GPIO pin could be badly damaged causing
all sorts of strange issues.