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Sync between two GPS

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francois.hamard:
Hello,


We want to integrate the GPS BU-353-S4 on our system and we want to synchronize our system with the GPS time. On the specification datasheet on your GPS, it is written that it is 1 micro-second synchronized. Nevertheless the tests we ran show that two GPS on the same system emit GGA frame with more than 200ms difference. Moreover, there is 90ms difference per hour between emission of two GGA frame. We have almost the same result with RMC frame.

Do you know a way to configure your GPS to be very precise on the publication of GPS time on serial port?
Thank you in advance,
François .

Hereunder log of the tests:
25/03/13 18:28:54:032 - INFO  - << RMC | /dev/ttyUSB7 | 17:28:53,000:2013-03-25
25/03/13 18:28:54:494 - INFO  - << RMC | /dev/ttyUSB8 | 17:28:54,000:2013-03-25
25/03/13 18:28:54:821 - INFO  - << GGA | /dev/ttyUSB7 | 17:28:54,000:
25/03/13 18:28:54:901 - INFO  - << GGA | /dev/ttyUSB8 | 17:28:55,000:
25/03/13 18:28:55:032 - INFO  - << RMC | /dev/ttyUSB7 | 17:28:54,000:2013-03-25
25/03/13 18:28:55:064 - INFO  - << RMC | /dev/ttyUSB8 | 17:28:55,000:2013-03-25
25/03/13 18:28:55:822 - INFO  - << GGA | /dev/ttyUSB7 | 17:28:55,000:
25/03/13 18:28:55:900 - INFO  - << GGA | /dev/ttyUSB8 | 17:28:56,000:
25/03/13 18:28:56:032 - INFO  - << RMC | /dev/ttyUSB7 | 17:28:55,000:2013-03-25
25/03/13 18:28:56:063 - INFO  - << RMC | /dev/ttyUSB8 | 17:28:56,000:2013-03-25
25/03/13 18:28:56:821 - INFO  - << GGA | /dev/ttyUSB7 | 17:28:56,000:
25/03/13 18:28:56:901 - INFO  - << GGA | /dev/ttyUSB8 | 17:28:57,000:
...
26/03/13 11:22:38:465 -  << RMC | /dev/ttyUSB7 | 10:22:39,000:2013-03-26
26/03/13 11:22:39:069 -  << GGA | /dev/ttyUSB8 | 10:22:40,000:
26/03/13 11:22:39:231 -  << RMC | /dev/ttyUSB8 | 10:22:40,000:2013-03-26
26/03/13 11:22:39:300 -  << GGA | /dev/ttyUSB7 | 10:22:40,000:
26/03/13 11:22:39:463 -  << RMC | /dev/ttyUSB7 | 10:22:40,000:2013-03-26
26/03/13 11:22:40:085 -  << GGA | /dev/ttyUSB8 | 10:22:41,000:
26/03/13 11:22:40:248 -  << RMC | /dev/ttyUSB8 | 10:22:41,000:2013-03-26
26/03/13 11:22:40:318 -  << GGA | /dev/ttyUSB7 | 10:22:41,000:
26/03/13 11:22:40:481 -  << RMC | /dev/ttyUSB7 | 10:22:41,000:2013-03-26
26/03/13 11:22:41:069 -  << GGA | /dev/ttyUSB8 | 10:22:42,000:
26/03/13 11:22:41:232 -  << RMC | /dev/ttyUSB8 | 10:22:42,000:2013-03-26
26/03/13 11:22:41:306 -  << GGA | /dev/ttyUSB7 | 10:22:42,000:

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