Pine64-LTS overlays for uart ports fixed!

[Kaya Saman]

On 7/31/19 4:32 PM, Ian Lepore wrote:
> 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 at 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).


Ok then I don't need to use it as my receiver isn't capable of anything 
below 20ms-1


http://static.garmin.com/pumac/GPS_18x_Tech_Specs.pdf


>
> 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?


I could try this though I'm not sure how to go about it. Would this be 
performed by the stty command? Currently -ixon is set on the port so 
that makes output control disabled. I could also try setting -ixoff to 
disable the input queue....


>
> 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 at 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
>

This might work better. I'll have a go later today. I did have issues 
while trying things out on Armbian so I don't know if it will the same 
case with FreeBSD. Virtually what happened was that setting the pin in 
the loader didn't take effect.


Thanks again Ian :-)


Best Regards,


Kaya