Marta was a firmware engineer for a small agricultural robotics startup. Her team had just switched from an old U-Blox GPS to the UG-353 (a common, low-cost 10Hz GPS module with a UART interface). The robot’s navigation stack was failing. “No fix,” the logs said. “No fix.”
The Silent NMEA Sentence
Still no fix in gpsd . Marta ran gpsd -N -n -D 5 /dev/ttyAMA5 (foreground, debug mode). The debug output revealed: ug-353 gps driver
gpsd: gpsd: command socket at /var/run/gpsd.sock gpsd: device /dev/ttyAMA5 is a UG-353 (NMEA) gpsd: no fix: no GPS signal But the UG-353 was outputting valid GGA sentences with a 3D fix. Why ignore them? She realized the UG-353 outputs , but gpsd ’s autobaud logic was misreading the sentence interval as corrupted data. She forced the baud rate and enabled raw NMEA mode : Marta was a firmware engineer for a small