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Re: [questions] Re: GPS+PPS vs NTP server, why a huge offset ?



Daniel O'Connor <darius@xxxxxxxxxxx> wrote:
> 
> 
>> On 17 Jun 2022, at 12:52, Jim Pennino <jimp@xxxxxxxxxxxxxxxxx> wrote:
>> Daniel O'Connor <darius@xxxxxxxxxxx> wrote:
>>> 
>>> 
>>>> On 17 Jun 2022, at 00:07, David Taylor <david-taylor@xxxxxxxxxxxxxxxx.invalid> wrote:
>>>> 
>>>> On 16/06/2022 10:00, Thiebaud HUMBERT wrote:
>>>>> To do the inversion, I just changed the "Pulse Mode" parameter to "Falling edge" from "Rising edge".
>>>>> The offset induced by the "pulse length" has disappeared.
>>>>> But there is still an offset of around 10.3ms, which I think is induced by USB as explained in this article about other chipsets (https://lists.freebsd.org/pipermail/freebsd-usb/2019- August/016078.html)
>>>> 
>>>> Yes, Thiebaud, USB is not good enough for PPS signals!
>>> 
>>> This is absolutely false.
>>> 
>>> If you are using it for NTP then GPS+PPS over USB is quite adequate (from personal experience).
>> 
>> As USB is a two wire interface, there is no such thing as PPS over USB.
> 
> The fact USB only has 2 data lines is irrelevant to wether you can send PPS over USB.
> 
>> You of course can get the ASCII data over USB, but to get a PPS signal
>> you in general have to hack a USB GPS and add a signal wire for PPS then
>> hack some interface on the computer to accept PPS.
> 
> This is absolutely not true in any meaningful sense.

OK, then to which of the USB connector pins do you connect the PPS
signal to get "PPS over USB"?
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