Date: Wed, 31 Jul 2019 09:32:38 -0600 From: Ian Lepore <ian@freebsd.org> To: Kaya Saman <kayasaman@optiplex-networks.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org> Subject: Re: Pine64-LTS overlays for uart ports fixed! Message-ID: <8e33e48f83f9a53015e165e53d4123c1c5b4e33e.camel@freebsd.org> In-Reply-To: <388e17e7-a277-9cd9-47ea-a38f10c7c741@optiplex-networks.com> References: <5f30c425-60c6-d54a-9593-2584bcf25925@optiplex-networks.com> <c601f08c4b3f1ad7beed5465622df37f583f844e.camel@freebsd.org> <09afae63-3583-46bd-8911-82a0f0a3185f@optiplex-networks.com> <2ab16425ac48bb7ff4365561b8959ee3eac50530.camel@freebsd.org> <388e17e7-a277-9cd9-47ea-a38f10c7c741@optiplex-networks.com>
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On Wed, 2019-07-31 at 16:17 +0100, Kaya Saman wrote:
> On 7/31/19 3:06 PM, Ian Lepore wrote:
> > On Wed, 2019-07-31 at 14:33 +0100, Kaya Saman wrote:
> > > On 7/31/19 1:42 AM, Ian Lepore wrote:
> > > > On Wed, 2019-07-31 at 00:46 +0100, Kaya Saman wrote:
> > > > >
[...]
> > >
> > > I am seeing this:
> > >
> > > gpsd:PROG: PPS:/dev/gps1 Assert cycle: 999973, duration: 799977 @
> > > 1564579823.472659791
> > > gpsd:PROG: PPS:/dev/gps1 Assert rejected missing last_fixtime
> > >
> > >
> > > Perfect ;-)
> > >
> > >
> > > I think I need to add pps_mode=0x11 or 17 in dec. as the pulse is
> > > inverted.
> > >
> > >
> > > This setup was working previously using a Prolific Serial to USB adapter
> > > for testing purposes as of course the USB introduces high latency.
> > >
> >
> > Actually, not so much as you'd think. I expected both high latency and
> > a lot of jitter when using a usb-serial for PPS, and what I found was a
> > fixed latency of less than a millisecond and jitter on the order of 60-
> > 80 microseconds. Even trying to saturate the usb bus by doing
> > continuous or bursty IO to a disk drive didn't noticibly increase the
> > pps latency or jitter. I was pretty surprised.
> >
> > -- Ian
> >
> >
>
> That's very interesting!
>
>
> My finding was that the accuracy went from the 10's of uS using a
> standard RS232 D-Sub port on one of my x64 systems to the 100's of uS
> range when switching to the Pine64 and using the USB->Serial adapter.
>
>
> Looks like the PPS signal just kicked in:
>
>
> gpsd:PROG: KPPS:/dev/gps1 Clear cycle: 999974, duration: 799981 @
> 1564585351.860177245
> gpsd:PROG: PPS:/dev/gps1 Clear cycle: 999974, duration: 799981 @
> 1564585351.860177245
> gpsd:PROG: PPS:/dev/gps1 Clear rejected this second already handled
> gpsd:PROG: KPPS:/dev/gps1 assert 1564585352.060170121, sequence: 5543,
> clear 1564585351.860177245, sequence: 5543 - using: assert
> gpsd:PROG: KPPS:/dev/gps1 Assert cycle: 999974, duration: 199992 @
> 1564585352.060170121
> gpsd:PROG: PPS:/dev/gps1 Assert cycle: 999974, duration: 199992 @
> 1564585352.060170121
> gpsd:PROG: PPS:/dev/gps1 Assert rejected 1Hz trailing edge
>
>
> After stopping the gpsd service and restarting it's finding it difficult
> to startup again. I attempted with dev.uart.4.pps_mode=0x21 for 'narrow'
> pulses even though 200ms-1 shouldn't be considered 'narrow'?? I'm guessing.
>
>
> Once I understand a little bit more about the behavior and quirks of the
> setup I'll probably start looking at how to enable an input switch on a
> GPIO pin then trying to get/write a driver for lcdproc and the Newhaven
> display. The aim is to use the retractive mechanical switch to change
> the LCD display from clock to GPS info....
> / {
> pps@0 {
> compatible = "pps-gpio";
> pinctrl-names = "default";
> pinctrl-0 = <&pinctrl_pps0>;
> gpios = <&gpio1 0 GPIO_ACTIVE_HIGH>; /* change this */
> status = "okay";
> };
> };
>
> The gpios= property will need to refer to the right bank and
>
> Still lots of work to go but it's definitely a really fun project :-)
>
>
> Regards,
>
>
> Kaya
I've never used gpsd and don't know how to interpret its output.
Narrow-pulse mode is for pulses down in the few-microseconds range
(professional timekeeping equipment often has very short pps pulses, in
the 1-100us range).
I've always been uneasy with the idea of using CTS for a pps signal,
since the uart hardware itself may want to use that line. I wonder if
it would help to use the .lock device to force off rtscts flow control?
Or, maybe even better, instead of using that pin as a uart cts signal,
maybe redo the pinmux to make it a gpio pin, then use the standard
gpiopps driver. You might need to add a symlink from /dev/gpiopps0 to
/dev/gps1 or whatever gpsd expects.
I'm not sure how to do the pinmux node for a gpio pin on that hardware,
but you can probably find an example of that. The dts source to enable
a gpio pin for pps is:
/ {
pps@0 {
compatible = "pps-gpio";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_pps0>;
gpios = <&gpio1 0 GPIO_ACTIVE_HIGH>; /* change this */
status = "okay";
};
};
The gpios= property will need to refer to the right bank and pin number
for that hardware.
-- Ian
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