The CPU temperature as measured by the on-CPU sensor went from about
55C to about 60C.
300MHz to 1GHz, ondemand, CPU in red http://dan.drown.org/bbb/run9/temp.png
1GHz fixed, CPU in red http://dan.drown.org/bbb/run8/temp.png
For current drain, I only have numbers at the wall wart measured by a
kill-a-watt. The entire system goes from 0.02A/1W to 0.04A/2W. Power
Factor is in the 0.5~0.4 region.
For the pins, that is correct. I chose P8.7 because it was TIMER4's
input, and I can switch between pps-gpio and pps-gmtimer by changing
which dts overlay I'm using.
Quoting Graham / KE9H <[email protected]>:
When you forced/locked the CPU frequency at 1 GHz, did you by any chance
measure what it did to the CPU case/package temperature? Or current drain?
I note that you used BBB pin P8.7 for PPS input. That allowed you to use
it for either
pps-gpio or TIMER4 pps-gmtimer, by just changing the pin-mux?
--- Graham
==
On Wed, Dec 10, 2014 at 7:58 PM, Dan Drown <[email protected]> wrote:
Quoting Paul <[email protected]>:
Using a PRU seems like overkill if all you want from the BBB is NTP. The
standard pps-gpio should move the system clock precision below
system/network jitter (.5 to 1 microsecond). The next step is using a
timer (TIMER4) which should get you into .1 microsecond offsets.
As a note to people wanting to use the timer hardware on the BBB - I have
a driver for it at https://github.com/ddrown/pps-gmtimer
I wrote up the results in using it at http://blog.dan.drown.org/
beaglebone-black-timer-capture-driver/
The summary of it is:
pps-gpio - 50% of the time local clock offset within +/- 0.07us, 98%
within +/- 0.61us
pps-gmtimer - 50% of the time local clock offset within +/- 0.04us, 98%
within +/- 0.43us
Also, if you're using pps-gpio, you might want to disable cpufreq and
force your processor to 1GHz. It'll help with interrupt latency and jitter.
cpufreq ondemand, 300MHz-1GHz - http://dan.drown.org/bbb/run9/
interrupt-latency.png
98% of interrupts handled 12.92us-23.21us after the event happened.
cpufreq forced 1GHz - http://dan.drown.org/bbb/run8/interrupt-latency.png
98% of interrupts handled 6.04us-8.58us after the event happened.
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