atbetaflight/docs/Gps.md

GPS

Two GPS protocols are supported. NMEA text and UBLOX Binary.

Configuration

Enable the GPS from the CLI as follows:

1. first enable the feature GPS
2. set the gps_provider
3. if required, set your GPS baud rate using gps_baudrate
4. connect your GPS to a serial port that supports GPS and set an approprate serial_port_x_scenario to 2. where x is a serial port number.
5. save.

Note: GPS packet loss has been observed at 115200. Try using 57600 if you experience this.

For the last step check the Board documentation for pins and port numbers and check the Serial documentation for details on serial port scenarios where you will also find some example configurations.

GPS Provider

Set the gps_provider appropriately.

Value	Meaning
0	NMEA
1	UBLOX

SBAS

When using a UBLOX GPS the SBAS mode can be configured using gps_sbas_mode.

The default is AUTO.

Value	Meaning	Region
0	AUTO	Global
1	EGNOS	Europe
2	WAAS	North America
3	MSAS	Asia
4	GAGAN	India

If you use a regional specific setting you may achieve a faster GPS lock than using AUTO.

This setting only works when gps_auto_config=1

GPS Receiver Configuration

UBlox GPS units can either be configured using the FC or manually.

UBlox GPS manual configuration

Use UBox U-Center and connect your GPS to your computer. The cli gpspassthough command may be of use if you do not have a spare USART to USB adapter.

Display the Packet Console (so you can see what messages your receiver is sending to your computer).

Display the Configation View.

Navigate to CFG (Configuration)

Select Revert to default configuration. Click Send.

At this point you might need to disconnect and reconnect at the default baudrate - probably 9600 baud.

Navigate to PRT (Ports)

Set Target to 1 - Uart 1 Set Protocol In to 0+1+2 Set Protocol Out to 0+1 Set Buadrate to 57600 115200 Press Send

This will immediatly "break" communication to the GPS. Since you haven't saved the new baudrate setting to the non-volatile memory you need to change the baudrate you communicate to the GPS without resetting the GPS. So Disconnect, Change baud rate to match, then Connect.

Click on PRT in the Configuration view again and inspect the packet console to make sure messages are being sent and acknowledged.

Next, to ensure the FC doesn't waste time processing messages it does not need you must disable all messages on except:

NAV-POSLLH
NAV-DOP
NAV-SOL
NAV-VELNED
NAV-TIMEUTC

The above messages should each be enabled with a rate of 1.

NAV-SVINFO

The above messages should each be enabled with a rate of 5 to reduce bandwidth and load on the FC.

When changing message target and rates remember to click Send after changing each message.

Next change the global update rate, click Rate (Rates) in the Configuration view.

Set Measurement period to 100 ms. Set Navigation rate to 1. Click Send.

This will cause the GPS receive to send the require messages out 10 times a second. If your GPS receiver cannot be set to use 100ms try 200ms (5hz) - this is less precise.

Next change the mode, click NAV5 (Navigation 5) in the Configuration View.

Set to Dynamic Model to airborne <1g and click Send.

Next change the SBAS settings. Click SBAS (SBAS Settings) in the Configuration View.

Set Subsystem to Enabled. Set PRN Codes to Auto-Scan. Click Send.

Finally, we need to save the configuration.

Click CFG (Configuration in the Configuration View.

Select Save current configuration and click Send.