SD card -image- for the beaglebone

[Iain Young]

On 06/02/13 04:18, Ian Lepore wrote:

> Check out what I taught my beaglebone to do today...
>
> root at bb:/ # ntpq -p
>       remote           refid  st t when poll reach   delay   offset  jitter
> ==========================================================================
> oPPS(0)          .PPS.        0 l    4   16  377    0.000    0.399   0.008
> +dvb.hippie.lan  .GPS.        1 u   55   64  377    1.411    0.666   0.126
> +tflex.hippie.la .GPS.        1 u   15   64  377    0.901    1.867   0.904
> +paranoia.hippie .PPS.        1 u   61   64  377    0.396    0.426   0.025
> xutcnist2.colora .ACTS.       1 u   71   64  376   34.136  -11.277   4.656
> xnist1.symmetric .ACTS.       1 u   63   64  377   59.880   12.327   2.113
> -ntp.your.org    .CDMA.       1 u    4   64  377   51.185   -4.212   4.215
> xntp1.conectiv.c .IRIG.       1 u   51   64  377   99.067   17.784   3.445
>
> It turns out the chip has nice timer hardware that can latch the
> freeruning timercounter in response to the PPS signal.  That allows for
> a PPS driver that doesn't use interrupts at all.  The timecounter code
> has a specific interface for such hardware, but there isn't much example
> code in the base for how to use it.  Soon there'll be more.  :)
 >
> I'll attach a patch in case anyone else wants to play with this.  To use
> it, apply the patch, add "options PPS_SYNC" to the kernel config, and
> choose which timer pin you want to put the pps on.  The attached patch
> uses the timer4 pin, which is exposed on the P8 connector as pin #7.
> You can use any of the timer4-timer7 pins, just set the one you want to
> use to "input" in the dts and the driver will use it.

Thanks for that, looks great, and very interesting. I'll do more than
play with it (well when the 8 Gig card arrives anyway!)

First thought, extending for multiple PPS :) [Because I can :P]

Hopefully come the weekend I can rebuild the kernel using Tim's 8 Gig
image, with this patch, and some more bits in the dts. Oh, and test
with PHKs ntpns on DCF-77, assuming that module arrives as well.


All the Best

Iain