[ntp:questions] How to debug GPS PPS?
snews at lordynet.org
Sun Feb 14 23:07:12 UTC 2010
David Lord wrote:
> 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
Going back to your previous reply I can see NMEA driver
looks to be working ok and you just need to trim out
the offset. GPSD + SHM driver might work ok for this
without PPS to give you about 10ms offset or with PPS
any of GPSD + SHM, NMEA or NMEA + ATOM should get you
in low us range for offset.
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