[time-nuts] Arduino GPSDO with 1ns res TIC

Don Latham djl at montana.com
Thu Feb 13 12:01:36 EST 2014

There's an internal comparator interrupt hardware in the Atmel chip the
Arduino uses. It can be programmed using the IDE as well.

Chris Albertson
> On Thu, Feb 13, 2014 at 6:36 AM, paul swed <paulswedb at gmail.com> wrote:
>> Lars has done a very good job here and good to see the comments and
>> excitement.
>> Have to agree with HAL that holdover is far more than a second and I
>> am in
>> a good location with the GPS antenna at 90'. I see my 3801 go into
>> holdover
>> occasionally and its not seconds.
>> Cheapest tinker 10 Mhz is a Xtal with a varicap diode in circuit to
>> adjust
>> frequency.
>> Sub $ 5 I would guess.
>> I was intrigued by the Arduino also and then went looking for
>> information.
>> Just about drowned in whats out there and pricing for the chip is from
>> 99
>> cents to $5.
> You will need one of the larger chips for this.   Closer to $5 than 0.99
>> What bootloader X Y or Z. I like the pure chip 28 pin approach and do
>> appreciate that this won't be H maser accurate.
> The "boot loader" is built into the Arduino IDE.  It's a pull down
> from the Tools
> menu.  Just select "Tools->Burn Bootloader" and it works.  But you
> should never
> have to do this.  All Arduinos ship with a bot loader and  preloaded
> example
> program to blink an LED.
> Don't let at the information of the Internet about this overload you.
> All you
> need to know, can be found from the "help" menu item.
> If you remove all of Lars' data logging and mode setting (debug) stuff
> this is a
> very short and simple bit of software.
>> Looked at the schematic and would appreciate a more complete picture.
> There are only two ICs and he does not use even half
> of the pins.    I doubt that it is critical that you even use the same
> divider chip.
> He does leave out the details about th switches on lines A1..A5.  You
> can see where thet
> are read and what is done with the data but it would be nice to see a
> schematic.
> There is certain;y enough information posted to get one of these
> working.
> My plan is to build one and make changes one step at a time.  As I said
> there is enough information to do that.
>>> [Context is cheap VCXO]
>>> > When used inside a GPSDO it only has to "hold over" for one second
>>> until
>>> the
>>> > next correction.
>>> Only if you have a good antenna and/or antenna location.
> I'll use whatever is in the "junk box" for initial testing, then later
> the Rb oscillator.
> --
> Chris Albertson
> Redondo Beach, California
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"The power of accurate observation is commonly called cynicism by those
who have not got it."
 -George Bernard Shaw

Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
Skype: buffler2

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