SD card -image- for the beaglebone

[Warner Losh]

On Jan 31, 2013, at 8:36 AM, Ian Lepore wrote:

> On Thu, 2013-01-31 at 11:02 +0000, Iain Young wrote:
>> Hi Folks,
>> 
>> I have just taken delivery of a few Beaglebones that I am intending to
>> do some NTP Work. With FreeBSD having one of the better reputations
>> with regards to Time and PPS etc, I thought I would install FreeBSD on
>> at least one of them.
>> 
>> Unfortunately, all of the guides I've found all assume you have a
>> FreeBSD box already running. Unfortunately, I don't, and nor do I have
>> a spare x86 box to do so.
>> 
>> Does anyone have an *image* of a base install for a 4 Gig microSD
>> card that I can download ? Preferably with ssh and dhcp installed
>> (yes, I know about blowing away the keys), as that would avoid having
>> to rely on the console.
>> 
>> Quite happy to rebuild the kernel and world afterwards (yes, I know I
>> need an 8 Gig SD card), but it's just this bootstrapping problem thats
>> an issue...
>> 
> 
> So you're interested in a PPS driver for BeagleBone?  That would be fun
> to play with, I wonder what the BB's timer hardware looks like?  It'd be
> easy enough to do with a gpio interrupt I suspect, but the timing geek
> in me can't resist going for the nanosecond-accurate measurements when
> possible, even if it is kind of pointless for millisecond-accurate NTP.

You can drive ntpd's accuracy to microsecond or tens of microseconds with appropriate hardware. nanosecond accuracy help to steer the frequency estimate the kernel uses for time keeping, but that only helps a little since its frequency estimates are computed over hundreds of seconds.

Warner