[time-nuts] Re: 2nd Run of TimeHats

[James Perkins]

Interested in 1 for comparison with my existing setups.

I have an adafruit ultimate GPS hat, a Deegoo GT-7U GPS module board, and
I've been interfacing these with Raspberry Pi 4B and AVNET's MaaXBoard
IMX8M to compare responsiveness, using gpsd and chrony. The Pi claims very
stable operation, RMS Offset ~1us, Skew ~0.030 ppm. The MaaXBoard, even
with identical GPS attached, runs with ~90us RMS Offset, Skew ~4.7 ppm. I'm
suspecting the MaaXBoard's sampling of the PPS GPIO is low-frequency,
interrupt latency is large, its system clock is low resolution, or it is in
some sort of idle deep sleep mode that takes it a long time to recover
from, but I'm going to need to look into it more deeply, and that's why the
oscilloscope just arrived. I'd like the MaaXBoard to work because of the
IMX8's IEEE 1588 PTPv2 Ethernet MAC, but there are alternatives in this
price range like Atmel SAMA5D3.

Cheers,
James

On Mon, Apr 26, 2021 at 9:57 AM John Miller via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hello everyone,
>
> I’ve seen a number of messages lately that reference the TimeHat boards I
> put together a couple of months ago, with lots of positive feedback, which
> I really appreciate. The first run of boards I did sold fairly quickly, and
> based on a number of emails I have gotten lately there seems to be some
> renewed interest.
>
> As such, I’m going to order up another batch of PCBs and parts, but I’d
> like to get an idea of how many I need to order to satisfy current demand.
> The GPS modules come from China, so there is about a two or three week wait
> them, so I want to make sure I have enough.
>
> For those not familiar, you can learn more about the TimeHat here:
> https://millerjs.org/timehat
>
> Regards,
> John
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-- 
James Perkins <james at loowit.net>  KN1X  www.loowit.net/~james
2030 W 28th Ave, Eugene OR 97405       +1.971.344.3969 mobile