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Does the Adafruit Ultimate GPS Board output NMEA ZDA?
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Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by Zeroignite on Wed Mar 20, 2013 8:50 pm

Question about the Ultimate GPS Breakout:
Does this module send the GPZDA NMEA sentence? I know that the GPRMC sentence contains the time, but GPS time is currently different from UTC by 19s (blame leap seconds). The GPZDA sentence is corrected for that.

Might I need to do anything (like messing with the inputs or changing the baud rate) to receive the GPZDA sentence?
Thanks :)
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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by wethaguy on Wed Mar 20, 2013 9:26 pm

It's not officially supported in the GPS docs, but the GPS will output a ZDA sentence when you give it the MTK command. This is valid on the ultimate GPS MTK3339, the C version I believe, from about a year ago.

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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by Zeroignite on Sat Mar 23, 2013 2:27 pm

Hmmm, yeah, I'm looking through the datasheet on the GPS module included in the Ultimate GPS Board (MTK3339 based), and there's nothing on sending commands to the module or receiving the ZDA sentence. The datasheet has a link to contact the manufacturer to generate specific proprietary sentences, but if this is a solved problem I'd rather not pretend to be a company when I'm just a hobbyist.

Can you provide more information on the method you used?
Thanks!
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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by Zeroignite on Sat Mar 23, 2013 2:39 pm

EDIT: (sorry for double-post, I can't find the edit button on this particular forum. Is there one?)
Looks like I can set the module to output ZDA using the MiniGPS tool from the manufacturer. To connect to a COM port, would that mean plugging the GPS module directly into the TX and RX pins of the arduino and bypassing the ATmega in the same way as in the Direct Computer Wiring tutorial?
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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by adafruit_support_mike on Sat Mar 23, 2013 5:08 pm

Zeroignite wrote:EDIT: (sorry for double-post, I can't find the edit button on this particular forum. Is there one?)

It should be on the row of buttons at the upper-right-hand corner of each post.
When you void a product warranty, you give up your right to sue the manufacturer if something goes wrong and accept full responsibility for whatever happens next. And then you truly own the product.

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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by Zeroignite on Sat Mar 23, 2013 5:29 pm

mstone@yawp.com wrote:
Zeroignite wrote:EDIT: (sorry for double-post, I can't find the edit button on this particular forum. Is there one?)

It should be on the row of buttons at the upper-right-hand corner of each post.
Weird... I was digging around in the user control panel seeing if I could change the board theme... for some reason, now I see the button after changing the time zone of all things. Before, all I saw was the report button.
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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by Zeroignite on Mon May 13, 2013 4:37 pm

This is kind of problematic. I contacted GlobalTop support asking if they can help me get the ZDA sentence:

I am using the PA6H GPS module as packaged with Adafruit's Ultimate GPS Breakout for a long-term accurate real-time-clock. However, the GPRMC NMEA sentence currently provided by the module provides the GPS timestamp, which currently differs from UTC by 19 seconds (a difference which will only increase due to additional leap seconds). Therefore, I would like a way to make the gps module output the GPZDA sentence (no other information is required, and the send rate is noncritical). Ideally I'd like to do this through a PMTK command, but the provided datasheet includes nothing on the GPZDA sentence.


Their reply:
In this situation we will refer you back to Adafruit. As you are purchasing a comets unit that Alpha Micro does not support. I suggest you speak to one of there very competent engineers.


Any idea how I should proceed?
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Re: Does the Adafruit Ultimate GPS Board output NMEA ZDA?

by wethaguy on Mon May 13, 2013 8:04 pm

GT does not officially support the ZDA sentence output. However, $PMTK314,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0*29 will set the NMEA output to the ZDA sentence (or blow up your GPS, cause your feet to fall off and turn your dog against you). Use at your own risk.

Here's a link to a great source of information on MTK commands for NMEA sentence output: http://lmgtfy.com/?q=NMEA+sentence+MTK+command

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