Hi everyone,
I’m currently using BlueOS 1.4 with ArduSub 4.5.3 (STABLE) running on a Navigator.
The GPS module I’m using is GT-505GGBL5-DR-N (NMEA format), connected directly to the Raspberry Pi via Serial5.
When I connect the GPS directly to the Raspberry Pi and read the data using a Python serial script, the NMEA messages are received continuously and stably without interruption.
However, once I enable Autopilot (ArduSub), the GPS data becomes very unstable.
Here is what happens:
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The system detects satellites for about 3 seconds, then goes into a “No GPS” state for around 10 seconds.
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After that, it recovers briefly and repeats this cycle indefinitely.
Interestingly, the system works relatively stably when about 30–40 satellites are visible, but becomes unstable when 50–70 satellites are visible.
This makes me suspect that the large number of NMEA messages may be overwhelming ArduSub’s serial processing (possibly causing a buffer overflow).
What I’ve already tried:
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Set GPS_MIN_ELEV = 15 (to exclude low-elevation satellites)
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Set GPS_GNSS_MODE = GPS only
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Disabled GPS_AUTO_CONFIG = 0
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Checked wiring and recalibrated multiple times
None of these actions solved the issue.
At this point, I suspect either:
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NMEA message flooding is causing ArduSub to drop data, or
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There is a conflict between the GPS baudrate/protocol and ArduSub’s configuration.
If anyone has experienced similar behavior, or has successfully used an NMEA-type GPS (especially GT-505GGBL5-DR-N) with Navigator + BlueOS, I’d really appreciate your advice or any configuration tips.
Thanks in advance,