1. What can I do if Precis (BX305) cannot position?

The problem can be diagnosed by following procedure.

  • Check whether the indicator lights are blinking. If not, then check the power supply system (whether the wire is connected firmly).
  • Check whether the Precis is outputting NMEA data. If not, configure the output with configuration tools.
  • Check the NMEA data; if the NMEA does not contain valid data (e.g., $GPGGA,051502.00,,,,,0,00,99.99,,,,,,*7B), then check whether the antenna is connected to the Precis.
  • Check the NMEA sentence $GPGGA; if the GPS status section in $GPGGA is 1, it means the Tersus/Precis is working in point position mode. Then, check the status of the RTCM data stream. If the GPS status section is 4 or 5, it means the Tersus/Precis is working in relative positioning mode and everything is working. If the GPS status is 4, you will get a centimeter-level RTK fixed solution. If the GPS status is 5, you will get a sub-meter level RTK float solution.

Remark: the seventh section in $GPGGA sentence in the GPS status, which is after ‘E’ or ‘W’.e.g. $GPGGA, 092204.999 ,4250.5589, S, 14718.5084 ,E ,1 ,04 ,24.4 ,M, 19.7,M ,,, 0000*1F.

2. I can get an empty NMEA sentence from one of the units. But none of the commands I enter into the program are acknowledged, either on COM1 or COM2. What should I do?

The empty NMEA sentence is caused by a lack of visible satellites. Please ensure that the GNSS antenna is well connected to the board and that the GNSS antenna is located on an outdoor and open sky site. 

The lack of response is likely caused by the USB connector. The USB connector can only be connected to the COM1 port (the one next to the USB host port). If you connect to COM2, you will get no response.

Please check the wire order of the USB connector as well. The correct order from left to right is red, black, yellow, green, and blue. You can check whether all the wires are sturdily connected to the connector, especially the fourth wire (green one), as it controls command sending.

3. Why doesn’t the Precis-BX305 board output RTCM data after I key in the RTCM output-related commands?

This issue could be caused by a number of issues.

  • Fixing the coordinate is a prerequisite of RTCM output. Therefore, use the “fix position” command to fix the coordinate first.
  • Check the interfacemode. If the target serial port is not in the right mode, it may not output RTCM properly. Use the “interfacemode” command to set the serial mode.

4. Why can’t mission planner recognize my Precis-BX305 boards?

This issue could be occurring for the following reasons.

  • Check the power supply. The Precis-BX305 board’s power consumption is about 1.5w. Although Pixhawk can also supply power, we still recommend an external power source. A voltage transformer is recommended to convert the 12V power output from a battery to 5V. Then connect to the Precis-BX305 board.
  • Please check the baud rate settings in the mission planner. It cannot be recognized if an incorrect baud rate is used. By default, the baud rate of the Precis-BX305 COM1 port is 115200 bps.
  • Please check the NMEA output. The mission planner requires that the GPS sensors output a NMEA GGA sentence, RMC sentence, and VTG sentence at 5Hz. A missing VTG sentence or low update rate may cause recognition failure.
  • Check the NMEA talker. Pixhawk can only recognize the NMEA sentence with a GP NMEA talker. An incorrect NMEA talker may cause failure.

5. Why is my configuration lost after the board (Precis-BX305) is powered off?

You need to execute the “saveconfig” command to save your configuration to the non-volatile memory before powering off; otherwise, your configuration will be lost when the device is powered off.