device-tree on BeagleBone Black (enabling UART)

[Kristoff]

Hi Oskar,


Just a quick reply to thank you (and everybody else) for your help.

I managed to get everything working.

Now running FreeBSD 13,0 Beta 3.
Recompiled the kernel to include the dmtpps driver, and after adding a 
device-tree overlay file to map the correct pin to timer 5, PPS is now 
running.


It took some time to be sure that the PPS module was indeed running 
(ntpq did note a "o" in front of the ip-address, but I wasn't sure if 
this was due to the configuration or if it actually detected the PPS 
signal), but I found the "ppsapi/ppsapitest" tool which did show that 
the PPS kernel-module was indeed running.

Note,
While testing the pps module,  I did a quick script to pump out the pps 
statistics to thingspeak.

For who is interested, the graph is here:
https://thingspeak.com/channels/1321348/

This is the time-difference between the clock of the beaglebone black 
and the PPS signal.
It is in ns, so 500K is a time-difference of half a millisecond.

Some longer term trending (not yet in the graph) seams to indicate a 
daily variation in the time-difference.
I am not sure this is due to the beaglebone (temperature affects) or the 
changes in the GNSS satellites the receiver can pick up.


Anycase, all thanks for the help.
Learned a lot!


I've also moved a pi3 from linux to freebsd and it is running very nicely.
Keep up the great work! :-)


Kr.





On 21/02/2021 7:23 p.m., Oskar Holmlund wrote:
> 2021-02-19 00:52 skrev Kristoff:
>> Hi all,
>>
>> (inline comments)
>>
>> On 12/02/2021 3:15 a.m., Ian Lepore wrote:
>>>
>>>>> The beaglebone has a special pps driver that uses the am335x chip's
>>>>> timer hardware to measure the pps pulse time with better accuracy
>>>>> than
>>>>> the generic gpio-pps driver.  To use it, add
>>>>>
>>>>>     am335x_dmtpps_load=YES
>>>> At the same time I also wanted to try the pps driver you mention.
>>>>
(...)