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

[David Willmore]

Are you sure which edge of the 1 PPS signal is the timing indicator?
If you're using the wrong polarity (falling vs rising edge), then you
might be seeing strange results.  But that doesn't account for the
multiple pulses/sec.

On Thu, Nov 9, 2017 at 3:40 PM, stinga <address@hidden> wrote:
> On 09/11/17 20:20, Alexander Carver wrote:
>>
>> 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.
>>
> All good ideas, but nope. gps is running off 3.3 votlts and I have tested
> the GPIO pin.
>
> I need to put the gps PPS pin on a scope and see what it is doing.
>
>
> --
> 'ooroo
>
> Stinga...(:)-)
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