UBX-17053592 - R03
Early Production Information
Troubleshooting
Page 29 of 33
9
Troubleshooting
My application (e.g. u-center) does not receive anything
Make sure that the USB cable is properly connected to the evaluation unit and the PC. By default, the evaluation
unit outputs NMEA protocol on Serial Port 1 at 9600 Bd, or on the USB.
My application (e.g. u-center) does not receive all messages
When using UART, make sure the baud rate is sufficient. If the baud rate is insufficient, GNSS receivers based on
u-blox M8 GNSS technology
will skip excessive messages. Some
serial port cards/adapters (i.e. USB to RS232
converter) frequently generate errors. If a communication error occurs while u-center receives a message, the
message will be discarded.
My application (e.g. u-center) loses the connection to the GNSS receiver
u-blox M8 positioning technology and u-center have an autobauding feature. If frequent communication errors
occur (e.g. due to problems with the serial port), the connection may be lost. This happens because u-center and
the GNSS receiver both autonomously try to adjust the baud rate. Do not enable the u-center autobauding feature
if the GNSS receiver has the autobauding flag enabled.
The COM port does not send any messages
Be sure that the slide switch at the front side is set to RS-232/USB and not SPI.
Some COM ports are not shown in the port list of my application (e.g. u-center)
Only the COM ports that are available on your computer will show up in the COM port drop down list. If a COM
Port is gray, another application running on this computer is using it.
After installing USB driver for the first time by connecting EVK-M8BZOE to PC with USB cable, the cursor
on PC starts to jump around the screen
The syndrome is caused when the NMEA 0183 GNSS serial data is misinterpreted as a mouse data by the serial
port enumerator (serenum.sys), resulting in erratic mouse cursor activity. This typically happens if the GNSS receiver
sends NMEA data at startup of PC. Thus ensure the EVK is not connected to PC when PC starts up.
The position is off by a few dozen meters
u-blox M8 GNSS technology starts up with the WGS84 standard GNSS datum. If your application expects a
different datum, you’ll most likely find the positions to be off by a few dozen meters. Don’t forget to check the
calibration of u-center map files.
The position is off by hundreds of meters
Position drift may also occur when almanac navigation is enabled. The satellite orbit information retrieved from an
almanac is much less accurate than the information retrieved from the ephemeris. With an almanac only solution,
the position will only have an accuracy of a few kilometers but it may start up faster or still navigate in areas with
obscured visibility when the ephemeris from one or several satellites have not yet been received. The almanac
information is NOT used for calculating a position, if valid ephemeris information is present, regardless of the
setting of this flag.
In NMEA protocol, position solutions with high deviation (e.g. due to enabling almanac navigation) can be filtered
with the
Position Accuracy Mask. UBX protocol does not directly support this since it provides a position accuracy
estimation, which allows the user to filter the position according to his requirements. However, the “Position
within Limits” flag of the UBX-NAV-STATUS message indicates whether the configured thresholds (i.e. P Accuracy
Mask and PDOP) are exceeded.
TTFF times at startup are much longer than specified
At startup (after the first position fix), the GNSS receiver performs an RTC calibration to have an accurate internal
time source. A calibrated RTC is required to achieve minimal startup time.
Before shutting down the receiver externally, check the status in MON-HW in field “Real Time Clock Status”. Do
not shut down the receiver if the RTC is not calibrated.
