Hi!
If it is all the same for you, I prefer this thread continue in the open
as I am interested both in using an Arduino-like for my first GPSDO and
STM32 for event capture and timming.
Regards,
Edésio
On Mon, Apr 21, 2014 at 04:29:35PM -0400, paul swed wrote:
Good afternoon very interested
Good afternoon very interested in the work you are doing with the STM board.
As I mentioned far earlier in this thread I am attempting to use it to
correct the BPSK WWVB signal here. Initial thoughts were using FORTH to
program the STM board.
Very curious what you are using as examples.
My
Perhaps this thread should go off line not to distract from the originators
thread.
Regards
Paul.
On Mon, Apr 21, 2014 at 4:29 PM, paul swed paulsw...@gmail.com wrote:
Good afternoon very interested in the work you are doing with the STM
board.
As I mentioned far earlier in this thread I am
Actually GCC supporting Cortex. So, I am using Raisonance IDE plus GCC
Toolchain as a development environment. My current project functional
diagram is following:
+--- STM32 -- (Pulse Counter, TTL Generator, DDS
driver, GPSDO monitor)
GPSDO--LTC6957-3--| |
I was experimenting with the same setup for STM32 MCU. This
microprocessor has accept the sine wave from external OCXO or GPSDO. No
problem with this. The only thing: I was need to start MCU from slow
watch crystal first. And then switch it to work to external one. In
another case I got
Hi,
On 10/04/14 06:43, Tom Van Baak wrote:
You are right in the I don't even need data cycles. All I want is the
error which is 5,000,000 minus the count. this is hopefully zero.
Correct. Keep the counter running. No need to zero it, ever. Use differential
measurements. Essentially you are
On Sat, Apr 12, 2014 at 9:48 AM, Magnus Danielson
mag...@rubidium.dyndns.org wrote:
In fact a 5 bit counter is enough, and then a '373 to sample it. The
enable to the 373 needs to be synchronous to the 5/10 MHz clock, so a pair
of DFFs ('74) is needed to synchronize the PPS and another pair
- Original Message -
From: Chris Albertson albertson.ch...@gmail.com
To: Discussion of precise time and frequency measurement
time-nuts@febo.com; Magnus Danielson mag...@rubidium.dyndns.org
Sent: Sunday, April 13, 2014 12:30 AM
Subject: Re: [time-nuts] First success with very simple, very
t...@leapsecond.com said:
You only need enough bits to cover the worst case OCXO frequency drift or
the worst case GPS jitter error, per second. For example, if your OCXO stays
accurate to 1 ppm it can't possibly drift more than 1 us per second.
Similarly, it's a safe assumption that your GPS
To many ifs and you could The Arduino is what it is. There
is no capture register, no interrupt priorities and the counter is
16-bits and the overflow actually takes one cycle. The code is
posted. You can read it. Every second it does what is suggested and
computers the difference in
You only need enough bits to cover the worst case OCXO frequency drift or
the worst case GPS jitter error, per second. For example, if your OCXO stays
accurate to 1 ppm it can't possibly drift more than 1 us per second.
Similarly, it's a safe assumption that your GPS 1PPS stays within 1 us of
On Wed, Apr 9, 2014 at 11:18 PM, Hal Murray hmur...@megapathdsl.net wrote:
t...@leapsecond.com said:
You only need enough bits to cover the worst case OCXO frequency drift or
the worst case GPS jitter error, per second. For example, if your OCXO
stays
accurate to 1 ppm it can't possibly
A couple more comments on the Arduino...
1) Have you checked for glitches in your dual-DAC system? The Arduino API
is forcing you to make two successive calls to analogWrite(). I wonder if
there might be a glitch when the LSB carries/borrows into the MSB, since
each PWM is configured
and frequency measurement
Cc: Tom Van Baak ; Hal Murray
Sent: Thursday, April 10, 2014 12:11 AM
Subject: Re: [time-nuts] First success with very simple, very low cost GPSDO,
under $8
On Wed, Apr 9, 2014 at 11:18 PM, Hal Murray hmur...@megapathdsl.net wrote:
t...@leapsecond.com said
But I still need to count all the cycles in the second and can't just let a
8 or 16 bit counter run free. The reason is I don't know where the
overflow happens. Overflow is not in sync with PPS.
OK this might work. I hope it does as it would allow a bit of code to be
removed. Let's
Tom Harris celephi...@gmail.com
On 10 April 2014 16:35, Chris Albertson albertson.ch...@gmail.com wrote:
To many ifs and you could The Arduino is what it is. There
is no capture register, no interrupt priorities and the counter is...
There certainly is an input capture, and it makes
On Wed, Apr 9, 2014 at 11:43 PM, Tom Van Baak t...@leapsecond.com wrote:
You are right in the I don't even need data cycles. All I want is the
error which is 5,000,000 minus the count. this is hopefully zero.
Correct. Keep the counter running. No need to zero it, ever. Use
differential
In my case, the cold-start frequency of my OCXO with EFC at midpoint was off
sufficiently far that I needed a minimum number of remainder bits to know which
way to initially steer it. Don't recall the exact number I needed, but it was
more than eight at 10 MHz. Like this design, I had 16 bits
with very simple, very low
cost GPSDO, under $8
On Wed, Apr 9, 2014 at 1:04 PM, Tom Harris celephi...@gmail.com
wrote:
Another point with the software is that your handler for the PPS
just reads
the counter. This gives an offset between the PPS edge and the value
read,
as your software takes
, this works fine on a 32- or 64-bit cpu, but not on an 8- or
16-bit cpu.
/tvb
- Original Message -
From: d0ct0r t...@patoka.org
To: time-nuts@febo.com
Sent: Thursday, April 10, 2014 10:12 AM
Subject: Re: [time-nuts] First success with very simple, very low cost GPSDO,
under $8
I am
with very simple, very low cost
GPSDO, under $8
I am not sure about Arduino, but probably it too has so-called timer
overflow interrupt. If so, then its possible to use that other
interrupt and some long (lets say 32-bit) RAM variable to accumulate
real value of counter.
In one of my project I
hol...@hotmail.com said:
I'm not sure how the Arduino environment handles interrupts, but in C you
need to declare any variables altered by an interrupt as volatile so that
the compiler optimization routines know not to assume they contain known
values.
Good point.
Also any code that
On Wed, Apr 9, 2014 at 2:08 AM, Hal Murray hmur...@megapathdsl.net wrote:
hol...@hotmail.com said:
I'm not sure how the Arduino environment handles interrupts, but in C
you
need to declare any variables altered by an interrupt as volatile so
that
the compiler optimization routines know
On Tue, Apr 8, 2014 at 10:44 PM, Mark Sims hol...@hotmail.com wrote:
I'm not sure how the Arduino environment handles interrupts, but in C you
need to declare any variables altered by an interrupt as volatile so that
the compiler optimization routines know not to assume they contain known
On Wed, Apr 9, 2014 at 9:39 AM, Orin Eman orin.e...@gmail.com wrote:
On Wed, Apr 9, 2014 at 2:08 AM, Hal Murray hmur...@megapathdsl.net
wrote:
The order the interrupt routine updates the counter shouldn't matter since
it's atomic as far as the mainline code is concerned.
In my case it's
On Wed, Apr 9, 2014 at 2:08 AM, Hal Murray hmur...@megapathdsl.net wrote:
Also any code that accesses them needs to do so with interrupts turned
off... otherwise you can wind up with corrupted values.
Forgot if I made this point but in a GPSDO when the interrupt is caused by
the PPS, the
Actaully I don't care much about an off by one count because the problem
is corrected in the next second. If I happen to miss a count one second the
very next second this shows up as an extra count.I notice that something
like this happens every few hundred seconds.
I think you can
But I think you over looked one point that makes this project easier: We
KNOW 100% for certain that the interrupts happen only once per second. So
the foreground code knows for certain it has exclusive access to shared
variables for a given period of time. There is zero chance of a problem
If my one interrupt per second assumption is wrong the GPS is badly
broken and nothing I can do will make the gpsdo work. In a final
system I should try and detect violations of the assumption and go
into hold over mode. That said I tried a test where I took the
interrupt line in my hand and
On Wed, Apr 9, 2014 at 11:18 AM, Hal Murray hmur...@megapathdsl.net wrote:
I think you can turn that into a feature. Suppose you start with the
DAC/OCXO running at exactly 10 MHz, and the phasing such that you are right
on. Due to noise, the last count will be early and get counted half the
On Wed, Apr 9, 2014 at 1:34 PM, Hal Murray hmur...@megapathdsl.net wrote:
But I think you over looked one point that makes this project easier: We
KNOW 100% for certain that the interrupts happen only once per second.
So
the foreground code knows for certain it has exclusive access to
...@lloyd.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Wednesday, April 9, 2014 3:17 PM
Subject: Re: [time-nuts] First success with very simple, very low cost GPSDO,
under $8
On Wed, Apr 9, 2014 at 1:34 PM, Hal Murray hmur...@megapathdsl.net wrote
Another point with the software is that your handler for the PPS just reads
the counter. This gives an offset between the PPS edge and the value read,
as your software takes time to respond to the interrupt and read the
counter. In your code, it doesn't matter as you only have one interrupt.
Well, where interrupts are involved, NEVER assume something about how the
code SHOULD/MIGHT be working. It is easy enough to disable interrupts before
accessing the volatile variables and restore them afterwards. This is by far
the simplest and most reliable way to do it correctly (no messy
On Wed, Apr 9, 2014 at 1:04 PM, Tom Harris celephi...@gmail.com wrote:
Another point with the software is that your handler for the PPS just reads
the counter. This gives an offset between the PPS edge and the value read,
as your software takes time to respond to the interrupt and read the
From: Chris Albertson albertson.ch...@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Wednesday, April 9, 2014 6:35 PM
Subject: Re: [time-nuts] First success with very simple, very low cost GPSDO,
under $8
On Wed, Apr 9, 2014
From: Chris Albertson albertson.ch...@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Wednesday, April 9, 2014 6:35 PM
Subject: Re: [time-nuts] First success with very simple, very low cost GPSDO,
under $8
On Wed, Apr 9, 2014 at 1:04 PM
On Wed, Apr 9, 2014 at 11:03 AM, Chris Albertson
albertson.ch...@gmail.comwrote:
On Wed, Apr 9, 2014 at 2:08 AM, Hal Murray hmur...@megapathdsl.net
wrote:
Also any code that accesses them needs to do so with interrupts turned
off... otherwise you can wind up with corrupted values.
You are right in the I don't even need data cycles. All I want is the
error which is 5,000,000 minus the count. this is hopefully zero.
Correct. Keep the counter running. No need to zero it, ever. Use differential
measurements. Essentially you are using binary modulus arithmetic.
This
I just had some success with a new GPSDO based very much on Lars Walenius'
design
I cut his design and his software down to make it even more simple and cost
less. The controller is now well under $8. The software is also much
simpler and easy to read even if you are not a software guy.
Lars'
I'm not sure how the Arduino environment handles interrupts, but in C you need
to declare any variables altered by an interrupt as volatile so that the
compiler optimization routines know not to assume they contain known values.
Also any code that accesses them needs to do so with interrupts
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