Groundside Proposal

Owned by Anthony Luo
Last updated: 2022-10-15 by Kevin Huang
2 min read

Content

RC-Link and Telemetry

People say RFD900x is good so we are going with that. The RFD900x will handle both telemetry and RC-link.

We can use a USB to FDTI cable to connect and power the RFD900x from the PC, however to avoid brownouts, we might want to consider using an external power source. (To power off USB, a jumper is needed to connect pins 4 and 6)
(see the RFD900x hardware docs on how to wire up the USB to FDTI cable)

The default serial port settings are as follow:

  • 57600 baud, no parity, 8 data bits, 1 stop bit

We can then communicate with the RFD900x via a COM port? via UART

 

Configuration

To configure the RFD900x, either use the RFD900 Tools GUI, or more likely, AT Commands.
The sequence “+++” without quotes can be used in a serial terminal connected to the radio to enter AT command mode, and the “ATO” command will exit the mode.


For more information on AT commands see section 4.2 of RFD900x software docs
For an example of using the RFD900x using python see this repo

Connection

Assuming P2P connection between the ground station and the drone RFD900x

Assuming default baud rate of 57600 (not sure if this is good)


2 nodes who have compatible parameters and are within range should sync automatically, a solid green LED indicates success. This should be good enough for testing for now.

For better stability, set network ID to the same number on both nodes using the ATS3=X command to set the network ID to X [0,255]. Make sure to save configs using AT&W and then reboot modem ATZ

 

To communicate, exit AT Command mode and send information through serial.

In python, simply open a serial communication on the appropriate COM port.

Relevant Resources

RFD900x hardware docs

RFD900x software docs

Tracking Antenna

A directional antenna would be combined with 2 servos, controlling its pan(yaw) and tilt(pitch). (just yaw)


The antenna would have a GPS chip on board in a fixed location relative to the antenna. The distance and offset would be measured and inputted on the ground station, and sent to the Nucleo.

During operation, the ground station would stream the GPS position of the drone to the tracking antenna system. From there, simple trigonometry can be applied to find the correct pan and tilt.

Questions to be answered/Discussion needed

The tracking system is currently open-loop, which is probably fine since we have a 30~60-degree effective angle.

A camera might be added for debugging/verifying the tracking accuracy, but NOT for tracking (as it will probably be very bulky)

How effective is tracking antenna signal wise when there is no light of sight?

References

A Portable UAV Tracking System for Communications and Video Transmission (researchgate.net)

ihsanalhafiz/Antenna-Tracker-UAV: Design System of Directional Finder Based nn Coordinates Mobile Remote System Using Moving Object Prediction Algorithm (github.com)

Other

RC-Links:

 

Telemetry:

  • dragonlink, crossfire, rfd900x

  • Xbees

 

Video: