Quoting Hal Murray <hmur...@megapathdsl.net>:
e...@thyrsus.com said:
fudge 127.127.22.1 refid PPSU time1 0.100700
*Trailing* edge? That's disturbing. I thought previous observation had shown
that the Adafruit hat reports rising edge. If this so, whether we catch the
rising or falling edge is variable based on more things than just the
hardware type and life gets much more complcated.
The Adafruit HAT does the right thing.
We need to know the details of Dan's hardware setup. I think the context of
his fudge offset was with a non-HAT device.
You can flip the rising/falling aspect of the leading edge with an inverter.
The standard RS-232 level shifters include an inverter. If that's what's
going on, I would have fudged flag2 to use the falling edge rather than
fudging the time offset.
Yes, I had the wrong edge setup on my USB PPS configuration.
This is my new configuration:
fudge 127.127.22.1 refid PPSU time1 0.000550 flag2 1
I put a picture of the hardware, the timeline for the changes along
with the impact of those changes here:
https://dan.drown.org/rpi/usb-pps/
Quoting Gary E. Miller:
Or easier yet, you can change the pps_gpio parameters at boot to
look at the other edge.
This specific PPS is the USB UART (pps_ldisc), so it picks up both edges.
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