GPS

GPS features in Cleanflight are experimental. Please share your findings with the developers.

GPS works best if the GPS receiver is mounted above and away from other sources of interference.

The compass/mag sensor should be well away from sources of magnetic interference, e.g. keep it away from power wires, motors, ESCs.

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

Configuration

Enable the GPS from the CLI as follows:

1. configure a serial port to use for GPS.
2. set your GPS baud rate
3. enable the feature GPS
4. set the gps_provider
5. connect your GPS to the serial port configured for GPS.
6. save and reboot.

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

For the connections step check the Board documentation for pins and port numbers.

GPS Provider

Set the gps_provider appropriately, for example set gps_provider=UBLOX

GPS Auto configuration

When using UBLOX it is a good idea to use GPS auto configuration so your FC gets the GPS messages it needs.

Enable GPS auto configuration as follows set gps_auto_config=ON.

If you are not using GPS auto configuration then ensure your GPS receiver sends out the correct messages at the right frequency. See below for manual UBlox settings.

SBAS

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

The default is AUTO.

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=ON

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 gpspassthrough command may be of use if you do not have a spare USART to USB adapter.

Note that many boards will not provide +5V from USB to the GPS module, such as the SPRacingF3; if you are using gpspassthrough you may need to connect a BEC to the controller if your board permits it, or use a standalone UART adapter. Check your board documentation to see if your GPS port is powered from USB.

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 unneeded messages, click on MSG and enable the following on UART1 alone with a rate of 1. When changing message target and rates remember to click Send after changing each message.:

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

Enable the following on UART1 with a rate of 5, to reduce bandwidth and load on the FC.

NAV-SVINFO

All other message types should be disabled.

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 Pedestrian 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.

UBlox Navigation model

Cleanflight will use Pedestrian when gps auto config is used.

From the UBlox documentation:

• Pedestrian - Applications with low acceleration and speed, e.g. how a pedestrian would move. Low acceleration assumed. MAX Altitude [m]: 9000, MAX Velocity [m/s]: 30, MAX Vertical, Velocity [m/s]: 20, Sanity check type: Altitude and Velocity, Max Position Deviation: Small.
• Portable - Applications with low acceleration, e.g. portable devices. Suitable for most situations. MAX Altitude [m]: 12000, MAX Velocity [m/s]: 310, MAX Vertical Velocity [m/s]: 50, Sanity check type: Altitude and Velocity, Max Position Deviation: Medium.
• Airborne < 1G - Used for applications with a higher dynamic range and vertical acceleration than a passenger car. No 2D position fixes supported. MAX Altitude [m]: 50000, MAX Velocity [m/s]: 100, MAX Vertical Velocity [m/s]: 100, Sanity check type: Altitude, Max Position Deviation: Large

Hardware

There are many GPS receivers available on the market. Below are some examples of user-tested hardware.

Ublox

U-Blox

NEO-M8

NEO-7

NEO-6

Serial NMEA

MediaTek