Module Time Sync #48
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Why couldn't you connect it to a capture line on a free running timer?
- Prabal
…On Saturday, March 18, 2017, Joshua Adkins ***@***.***> wrote:
To have a hope of tight time synchronization, modules are probably going
to need to wire PPS to a timer/counter (TC) pin, so that it can trigger a
counter start. This might not really help, because the SAM4L doesn't have a
32bit counter that can take an external trigger anyways, but it's something
to think about.
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The only 32bit free running timer peripheral does not have any way to
interface with external i/o in hardware, and its fastest clock source is
32khz. I was going to test full accuracy of time-stamping events in
software using this timer today.
I expect to achieve synchronization in the 10s of uS using this method,
which is probably good enough for something like localizing an audio
source, but still much worse than our original expectation of
synchronization given the accuracy of the pps line.
On Mar 20, 2017 7:44 AM, "prabaldutta" <[email protected]> wrote:
Why couldn't you connect it to a capture line on a free running timer?
- Prabal
On Saturday, March 18, 2017, Joshua Adkins ***@***.***> wrote:
To have a hope of tight time synchronization, modules are probably going
to need to wire PPS to a timer/counter (TC) pin, so that it can trigger a
counter start. This might not really help, because the SAM4L doesn't have
a
32bit counter that can take an external trigger anyways, but it's
something
to think about.
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Wow...that's interesting and a bit disappointing that the MCU is missing
this pretty basic functionality. I'm surprised that there isn't a 32-bit
timer block that can be configured to be free running and that also gives
you a capture line.
- Prabal
…On Monday, March 20, 2017, Joshua Adkins ***@***.***> wrote:
The only 32bit free running timer peripheral does not have any way to
interface with external i/o in hardware, and its fastest clock source is
32khz. I was going to test full accuracy of time-stamping events in
software using this timer today.
I expect to achieve synchronization in the 10s of uS using this method,
which is probably good enough for something like localizing an audio
source, but still much worse than our original expectation of
synchronization given the accuracy of the pps line.
On Mar 20, 2017 7:44 AM, "prabaldutta" ***@***.***
***@***.***');>> wrote:
Why couldn't you connect it to a capture line on a free running timer?
- Prabal
On Saturday, March 18, 2017, Joshua Adkins ***@***.***
***@***.***');>> wrote:
> To have a hope of tight time synchronization, modules are probably going
> to need to wire PPS to a timer/counter (TC) pin, so that it can trigger a
> counter start. This might not really help, because the SAM4L doesn't have
a
> 32bit counter that can take an external trigger anyways, but it's
something
> to think about.
>
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Yeah, I was pretty shocked. Usually you can at least chain two 16bit timers
together in hardware, and I can't even find a way to do that.
I might resort to running our synchronization evaluation code on the
cc2538, but I haven't looked into it much yet. Hopefully that would at
least allow us to demonstrate the capabilities of the platform, even if
most of the modules we currently have can't achieve that accuracy.
…On Mar 20, 2017 8:24 AM, "prabaldutta" ***@***.***> wrote:
Wow...that's interesting and a bit disappointing that the MCU is missing
this pretty basic functionality. I'm surprised that there isn't a 32-bit
timer block that can be configured to be free running and that also gives
you a capture line.
- Prabal
On Monday, March 20, 2017, Joshua Adkins ***@***.***> wrote:
> The only 32bit free running timer peripheral does not have any way to
> interface with external i/o in hardware, and its fastest clock source is
> 32khz. I was going to test full accuracy of time-stamping events in
> software using this timer today.
>
> I expect to achieve synchronization in the 10s of uS using this method,
> which is probably good enough for something like localizing an audio
> source, but still much worse than our original expectation of
> synchronization given the accuracy of the pps line.
>
>
> On Mar 20, 2017 7:44 AM, "prabaldutta" ***@***.***
> ***@***.***');>> wrote:
>
> Why couldn't you connect it to a capture line on a free running timer?
>
> - Prabal
>
> On Saturday, March 18, 2017, Joshua Adkins ***@***.***
> ***@***.***');>> wrote:
>
> > To have a hope of tight time synchronization, modules are probably
going
> > to need to wire PPS to a timer/counter (TC) pin, so that it can
trigger a
> > counter start. This might not really help, because the SAM4L doesn't
have
> a
> > 32bit counter that can take an external trigger anyways, but it's
> something
> > to think about.
> >
> > —
> > You are receiving this because you are subscribed to this thread.
> > Reply to this email directly, view it on GitHub
> > <#48>, or mute the thread
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> > .
> >
>
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Probably not a bad idea. Our module selection kinds undercuts the basic
claim.
It might be useful to just do this on some third-party module that runs its
own ecosystem (e.g. mbed, Arduino, TI, etc.) to demonstrate both the timing
and the modular compatibility.
- Prabal
…On Monday, March 20, 2017, Joshua Adkins ***@***.***> wrote:
Yeah, I was pretty shocked. Usually you can at least chain two 16bit timers
together in hardware, and I can't even find a way to do that.
I might resort to running our synchronization evaluation code on the
cc2538, but I haven't looked into it much yet. Hopefully that would at
least allow us to demonstrate the capabilities of the platform, even if
most of the modules we currently have can't achieve that accuracy.
On Mar 20, 2017 8:24 AM, "prabaldutta" ***@***.***
***@***.***');>> wrote:
> Wow...that's interesting and a bit disappointing that the MCU is missing
> this pretty basic functionality. I'm surprised that there isn't a 32-bit
> timer block that can be configured to be free running and that also gives
> you a capture line.
>
> - Prabal
>
> On Monday, March 20, 2017, Joshua Adkins ***@***.***
***@***.***');>> wrote:
>
> > The only 32bit free running timer peripheral does not have any way to
> > interface with external i/o in hardware, and its fastest clock source
is
> > 32khz. I was going to test full accuracy of time-stamping events in
> > software using this timer today.
> >
> > I expect to achieve synchronization in the 10s of uS using this method,
> > which is probably good enough for something like localizing an audio
> > source, but still much worse than our original expectation of
> > synchronization given the accuracy of the pps line.
> >
> >
> > On Mar 20, 2017 7:44 AM, "prabaldutta" ***@***.***
***@***.***');>
> > ***@***.***
***@***.***');>');>> wrote:
> >
> > Why couldn't you connect it to a capture line on a free running timer?
> >
> > - Prabal
> >
> > On Saturday, March 18, 2017, Joshua Adkins ***@***.***
***@***.***');>
> > ***@***.***
***@***.***');>');>> wrote:
> >
> > > To have a hope of tight time synchronization, modules are probably
> going
> > > to need to wire PPS to a timer/counter (TC) pin, so that it can
> trigger a
> > > counter start. This might not really help, because the SAM4L doesn't
> have
> > a
> > > 32bit counter that can take an external trigger anyways, but it's
> > something
> > > to think about.
> > >
> > > —
> > > You are receiving this because you are subscribed to this thread.
> > > Reply to this email directly, view it on GitHub
> > > <#48>, or mute the thread
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> > lLeQVFRWu6WIw1NwqF5dGFwks5rm2Z7gaJpZM4MhTAW>
> > > .
> > >
> >
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> > <#48 (comment)>,
or
> > mute
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To have a hope of tight time synchronization, modules are probably going to need to wire PPS to a timer/counter (TC) pin, so that it can trigger a counter start. This might not really help, because the SAM4L doesn't have a 32bit counter that can take an external trigger anyways, but it's something to think about.
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