11 Oct
2014
11 Oct
'14
12:23 a.m.
Winfried Ritsch:
Am Sonntag, 5. Oktober 2014, 23:35:21 schrieb
tom(a)trellis.ch:
The arm's I used ([b]) have an PLL at the clock input and a few multiplier
and prescalers, so if you have a clock from a PTP tranceiver ([a] have
a clock output of 125MHz scaled down by 2..255). So sync. should be
possible.
According to {b] p.939, they (if they have ethernet) supports PTP directly.
On Sun, October 5, 2014 22:25, Fons Adriaensen
wrote:
just to add another options and be a wiseacre :
On a microchip dsPIC [1] you can adjust the internal oscillator (RC) (where
also the sample clock for DA is derived) in a small range of 10%, so it is
possible to use PTP for sample-exact synchronization (I did do a "soft PLL"
for a low cost solution of a DA to avoid re-sampling and big buffers). I was
told on ARMs Oscillator tuning is also possible, and if audiohardware derives
clocks from it, it can also be tuned and used as soft PLL. On Sun, Oct 05, 2014 at 08:39:11PM +0200,
tom(a)trellis.ch wrote:
Sounds interesting. I asked myself if it would be possible to drive the
audio interface clock by the host (not by a wordclock coming from another
audio interface which makes the "network" case local again to some
degree), i.e. through ticks sent via FW/USB.
As a scenario, at point a) an analog signal is
injected that will be
played back (analog) at point b) with the lowest possible (and constant)
latency. How do you intend to handle diverging clocks of the audio
interfaces (ADC/DAC) at both (a/b) ends?
Either
1. Sync the HW sample rates to an explicit or implicit reference
provided by the network protocol. Requires special audio HW. A few normal
audio interfaces (e.g. some RME cards) would allow to do this as well, but
I know of no software that uses this
capability. Anyway there are Chips [2] which can generate
sample-clocks (Master-Clock)
from a PTP signal, so if your audiohardware supports Master-Clock, you can add
such a chip ;-).
...
[1]
http://ww1.microchip.com/downloads/en/DeviceDoc/39700c.pdf page 10
[2] http://en.wikipedia.org/wiki/List_of_PTP_implementations#silicon
I only found [a], perhaps another distributer.
//// {another mail}
Thanks for the link.
Regards,
/Karl Hammar
[a]
http://se.farnell.com/texas-instruments/dp83640tvv-nopb/ic-ethernet-cont-ie…
[b]
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/REF…
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