[time-nuts] GPS seconds conversion on an Arduino

Jay Grizzard elfchief-timenuts at lupine.org
Mon May 15 02:44:24 EDT 2017

Also consider the $16 Chip Pro (https://getchip.com/pages/chippro), 
which runs linux and thus lets you write normal code for the normal

They also have a $9 more arduino-like version (still runs linux)


On Sun, May 14, 2017 at 11:22:57PM -0700, Chris Albertson wrote:
> Are you still going for Sidereal time?  If so that is floating point
> The ARM processor unlike the Arduino does not have fixed pin assignment.
> Typically there are many UARTS, I2C interfaces, ADC units and so on more
> than there are physical pins.  Within some limits you assign functions to
> pins in software.    Some you don't need to make a special board at OSHPark
> with three serial ports.   You can move the serial function to the pins you
> like.
> That said, moving functions to pins is an "advanced" software art.  So to
> make it easy for normal people the development environment will have some
> easy way to do this and some limits too.
> You can program most ARM M boards using Arduino but that IDE while day to
> use is limited.   The next step up is "mbed" which is much more capable and
> lets you move some functions to some pins the IDE is web based so there is
> no software to install.   (OK you can work locally if you like.  There are
> several ways to do that.
> This is my favorite under $2 boards now
> http://www.ebay.com/itm/STM32F103C8T6
> <http://www.ebay.com/itm/STM32F103C8T6-ARM-STM32-Minimum-System-Development-Board-Module-For-Arduino-/192181979870?hash=item2cbef04ade:g:pBgAAOSwvihY8r-0>
> The specs are literally an order of magnitude over Arduino and at under $2
> shipped thrice is right.   These are Arm Cortex M3 in the size of a large
> 1970's vintage DIP chip.  Google the P/N for loads of information    This
> parts works on bed and arduino IDEs   as well as simply using the gcc arm
> compiler.
> The other one I use is Nucleo F401RE
> These are $13 each and unlike the above have loads of 1st rate
> documentations written by a US company ST Micro.
> https://developer.mbed.org/platforms/ST-Nucleo-F401RE/
> Yes you can snap off the programmer and reconnect it with jumpers or leave
> it on.   Even if you leave it on you can use it to program the STM32F103.
> Saves you from having to buy an Chinese clone ST-Link dongle.
> TheF401RE is the "classic" part that most example programs have beed tested
> on but I'd buy the F446RE for $1 more.  It's twice as fast and has more RAM.
> The mbed IDE lets  you use most C source code you can find and it runs a
> real time OS.    Arduino is still hands down the easiest environment to
> learn and it runs at 5 volts.  I keep one for testing 5V hardware.  All the
> arm stuff is 3v3
> Most any ARM board can run with the Arduino IDE it some one wrote a boot
> loader for it.  The mbed boards don't use bootloders.  They "look" like a
> flash drive to your PC so all you do is drag and drop the BIN file to the
> flash drive and the board then runs whatever case to dropped there.
> One more bit of advice.  Buy a logic analyzer.   I was using one today and
> mad it save a LOT of time debugging when you can see what data is on the
> pins.  Logic analyzers used to be expensive but one god enough for this
> kind of work is now under $10 for a Saleae clone
> http://www.ebay.com/itm/24MHz-8CH-USB-Logic-Analyzer-24MHz-8-Channel-Compatible-to-Saleae
> <http://www.ebay.com/itm/24MHz-8CH-USB-Logic-Analyzer-24MHz-8-Channel-Compatible-to-Saleae-ARM-FPGA-M100-/272337085235?hash=item3f688e2333:g:RNcAAOSwPCVYBD2b>
> They work like a scope for digital and can do protocol decoding show the
> data going over a cable.
> On Sun, May 14, 2017 at 2:16 PM, Ben Hall <kd5byb at gmail.com> wrote:
> > Hi Chris and list,
> >
> > My original goal was to duplicate, more or less, what the PackRat guys did
> > to get the TruePosition boards up and functional as described here:
> >
> > <http://www.packratvhf.com/A%20Packrat%20GPS%20Receiver%20Project.pdf>
> >
> > I did get in touch with them and they forwarded the HEX files.  I haven't
> > tried them yet, but another list member did try them without success.
> >
> > I figured, as a learning exercise, I'd program up my own interface.  The
> > boards do not talk NMEA...but output their own format of message.  One
> > message contains GPS time in seconds...plus the number of leap seconds that
> > have elapsed, so my goal there was to convert the GPS time from the unit
> > into normal UTC date and time.
> >
> > On 5/14/2017 12:38 PM, Chris Albertson wrote:
> >
> >> Unless this is an educational exercise I'd move to a different processor.
> >> One of those $3 Arm M3 units has enough  memory AND a more standard
> >> development environment that you could use a standard library function to
> >> do what you need.
> >>
> >
> > It is an educational exercise...but I'm still going to look into this.
> > Another list member suggested a different Arduino board that had two real
> > serial ports, as right now the Uno board I'm using only has one hardware
> > serial port with a second duplicated in software.  (one port talks to the
> > TruePosition board...the other is debugging output port)
> >
> > I did happen to recall that I included a Teensy-LC board (Cortex M0) in a
> > recent OSHPark PCB order...and it appears to have three hardware serial
> > ports...so this may be the way I go eventually.
> >
> > One of the reasons I liked the Uno was due to all the tutorials and
> > example code floating around...plus the nice selection of libraries...as
> > I'm not a programmer.  My code would probably make a real programmer lose
> > his or her lunch.  :(
> >
> > thanks much,
> > ben
> > _______________________________________________
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> >
> -- 
> Chris Albertson
> Redondo Beach, California
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