device-tree on BeagleBone Black (enabling UART)

[Kristoff]

Hi Daniel,



Thank you for the very fast reply!


(inline comments)


On 7/02/2021 1:10 a.m., Daniel O'Connor wrote:
>> On 7 Feb 2021, at 10:28, Kristoff <kristoff at skypro.be> wrote:
>> I am running FreeBSD 12.1 on a beaglebone black. As I want to use it for a time-server (i.e. connect it to a GPS), I want to enable an additional UART (and also a pps gpio-pin, I guess).
> I have done this, although my kernel is..
> FreeBSD gps 13.0-CURRENT FreeBSD 13.0-CURRENT #2 41a4c010326-c262109(master)-dirty: Mon Sep  9 10:05:18 ACST 2019     darius at midget.dons.net.au:/usr/obj/arm-src/arm.armv7/sys/GENERIC  arm


OK, 12.1 just happens to be the version I had installed after playing 
around with different releases.

I'll install 13.0 on the BBB.


> I applied some fixes which have since been committed.
>
>> I have been trying to create a DTS-overlay file for this, but for some reason, I do not get this OK.
>> The overlay file (see below) I use is below.
>> Some remarks:
>> - I compile the blob with dtc, copy the file to /boot/DTB and modify /boot/loader.conf
>> I guess this is correct?
> I never got an overlay working so I modified am335x-boneblack.dts manually..

Thx!

I found some posts from people who converted the .dtb to .dts and 
modified it overthere, but I wanted to do this the proper way.

What is strange is that certain device-tree overlay's do work. I found 
one for the pruss blocks in the am3358 and that one does seams to work.

(small side-line question: is there application-level support for the 
pruss blocks in the BBB on freebsd?)

Thanks for the change-files. I'll examine them and try them out.



> If you load am335x_dmtpps.ko it then shows up as /dev/dmtpps, I then have these symlinks:
> lrwxr-xr-x  1 root  wheel  5  3 Jan 04:01 /dev/gps0 -> cuau2
> lrwxr-xr-x  1 root  wheel  6  3 Jan 04:01 /dev/gpspps0 -> dmtpps
> And ntpd.conf has:
> # NMEA on /dev/gps0 at 9600 baud, process GPGGA only (offset is time2)
> # PPS on /dev/gpspps0 (offset is time1, PPS enabled by flag1)
> server 127.127.20.0 mode 0x12 minpoll 4 maxpoll 4
> fudge  127.127.20.0 time1 0.000 time2 0.332 flag1 1 stratum 0 refid GPS
>
> [gps 0:08] ~ >ntpq -nc pe
>       remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> o127.127.20.0    .GPS.            0 l    5   16  377    0.000    0.028   0.004

Thx.


> My GPS engine is a u-Blox NEO-M8T (from https://www.gnss.store/gnss-gps-modules/45-ublox-neo-m8t-time-raw-receiver-board-with-sma-rtk-ready.html)

It's the same one I have.


I really like that chip as you can use it to receive the raw packets as 
transmitted by the satellites!
I have also used to inject dgps signals (as received by  the maritime 
dgps transmittors with a rtlsdr and some gnuradio) into it and the chip 
does use to them to increase correct the GPS signals.


Thanks for the help!



Cheerio! Kr. Bonne