This weekend we decided to use our GPS sync and Top of the Minute impusle features of the TIMY to set our clocks for a scored college race. We sync'd a TIMY with a GPS puck and then used the TIMY to throw top of the minute impulses for the sync and +1 for our A and B clocks. The TD was shocked with the +1 times being to within the 1/10,000 of the whole minute. We also used it to sync our start beep to keep it on the same page (and to identify early and late starts).

I need some help with this one.

I was using a Garmin GPS18C ‘puck’ type of GPS running at 4800 baud. I had to set the RS232 port to 4800 (9600 is now the default after a new firmware update) and it recognized the GPS on the next restart, so the Baud rate worked. I couldn’t exit the Sync screen. Did I miss something? The only way I could get out of it was by sending a pulse on C0.

The GPS that Alge is selling is running at 9600 baud. I know from talking to Albert, that they are looking for a $GPRMC sentance and a valid satellite signal (this sample is not valid).

Mike


$GPRMC,142933,V,4430.8098,N,08019.7585,W,,,090307,010.2,W*64

$GPGGA,142933,4430.8098,N,08019.7585,W,0,00,,,M,,M,,*44

$GPGSA,A,1,,,,,,,,,,,,,,,*1E

$GPGSV,3,1,12,02,37,244,00,04,83,269,00,05,21,315,00,09,14,263,00*74

$GPGSV,3,2,12,12,29,313,00,13,00,111,00,17,56,091,00,20,20,043,00*7B

$GPGSV,3,3,12,23,05,082,00,28,11,157,00,30,00,325,00,48,17,242,00*74

$PGRME,,M,,M,,M*00

$GPGLL,4430.8098,N,08019.7585,W,142933,V*24

$GPVTG,,T,,M,,N,,K*4E

The usefulness of the GPS synch feature is lost on me. I guess it might be useful for something like rally-raid timing, where the Stage Start and Stage Finish timing crews are 600 km apart? I can't imagine a situation where it would be of much use, but I guess it's nice to know it's there.

On the other hand, the "Johnny Appleseed" feature of the Timy (impulse on channel 0 at Top Dead Center when holding down green & red OK) is *extremely* useful. Once you get a "reference Timy" going, it doesn't matter whether the reference is synched in any semblance to UTC or local time, as long as all your time bases match the reference, and therefore each other.

In any event, looking through the Garmin docs, the contents of the $GPRMC packet is dangerously misleading. Param #1 is the UTC time, and Param #2 is the Status Tag. You would think a Status Tag of "V" (as in Mike's example above) means "Valid", but the opposite is true. "V" is a "validity warning". "A" means the GPS is synched up.

Most GPSs have some non-volatile memory, so they "remember" the UTC time - but with substantial drift. Until that $GPRMC param #2 turns from "V" to "A", the GPS time is going from memory, not from the satellite, and may be off substantially. If the GPS has been moved or reset, then the UTC may start from 000000. The Garmin docs state that a full satellite synch from scratch takes about 5 minutes from the time the GPS is powered up and has a view of the sky.

Thanks Big Guy.. .trust you to catch the V vs A in the sentance!

I knew I was going to get in trouble posting that actual stream from my Garmin. I just didn't want to stand outside in the +14C rain here in Toronto (isn't this winter) to catch a valid signal. I thought I would hack the V to a A, but the Checksum at the end would have been wrong.

However, I couldn't agree with you more with having the top of minute function the most important feature. We use it all the time.

Short story, I was just doing it because it was there. Not really required for Ski Racing other than to rapidly resync a Timy at the start for a backup device (like hand timing or connected to a start wand for the 5th + backup system).

Mike