[ntp:questions] How to debug GPS PPS?

David Lord snews at lordynet.org
Sun Feb 14 22:58:41 UTC 2010

xyz-2041 wrote:
> Thanks for your responses, guys.  Will reply in the future.
> Tried Garmin software to try to talk to the unit on a
> Windows box:
>    <https://buy.garmin.com/shop/store/downloadsUpdates.jsp?
> product=010-00124-00&cID=170&pID=70>
> None of these 3 programs worked.
> Tried MS Hyperterminal.  No good.
> Tried RealTerm (<http://realterm.sourceforge.net/>).  Got to see
> the messages once I got it working at 4800.  RealTerm shows
> the dataflow just like a breakout box.  Saw that it is *not* sending
> PPS on pin 1.  Just sending messages on pin 2.

What sentences is it sending NMEA or binary?

How do you have the unit wired to the serial port?
The JST has pins 1-12 1=TxD2 2=RxD2 3=PPS 4=TxD1 5=TxD2
6=PD 7=AuxBat 8=GND 9/10=3.6 to 6V 11=nc 12=NMEA-out(cmos)

You need to check on below, it's best I can work out

ie JSTpin      D9pin
      3 --------- 1
      4 --------- 2
      5 --------- 3
      8 ---+----- 5
           +---- 0V
     10 -------- +3.6 to +6V

CMOS generated RS232 levels should be ok but depends on
serial port of your pc. PPS out to DCD is given as 700mVp-p
into 50r so will need converting to rs232.

> Tried to send  a message to change to 9600, and turn PPS on.
> Ignored messages because of improper syntax.  Needs
> proper checksum.

I have a gwbasic program for working out required messages.
GPSD will do it for you. Garmin site also have a windows
utility for generating required commands with checksum.

> Does anyone know of software that actually works with this
> unit?



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