mavleash

Author: Todd Stellanova todd@droneflow.com
License: MIT

Description

This Particle application allows you to monitor the status of your drone, including position, velocity, and battery level, anywhere there is cellular network coverage. The name mavleash derives from "Micro Air Vehicle Leash".

Mavleash uses the Particle.io Electron board , with the associated cellular data plan, to maintain two-way radio contact with your drone, even if you lose your RC connection. Unlike traditional telemetry radios such as SiK, the range of the Electron is only limited by the availability of mobile phone towers.

Compatibility

This project uses the mavlink protocol v1.0 to communicate with any drone that supports it (there are many). For my testing I've used standard Pixhawk v2.4.6 autopilot hardware and the latest "Stable" PX4 firmware build installed using QGroundControl.

Building and Flashing

Currently you will need to build using the Particle command line tools:

cd /firmware
rm *.bin
particle compile electron .
particle flash <electron device ID> electron_firmware_*.bin

Assuming your Electron is connected to the cellular network (the status LED is "breathing cyan"), you can flash your Electron over the cellular connection (data usage charges apply).

Wiring

This application connects from the drone's mavlink serial output port to the serial UART port of the Electron (RX, TX, GND, VIN). Assuming you've already configured your drone to output mavlink on the serial port (not USB), you need only run four wires from the drone's port to the Electron pins. In my testing I found it adequate to attach the Electron's VIN to the Pixhawk's 5V output line on the TELEM1 port.

Note that you can just as easily use a Particle Photon for prototyping and testing, as I did. This uses WiFi instead of cellular data, possibly saving your some data usage during your prototyping phase.

Tip: If you think you've wired up everything correctly and you're not receiving any data from the Electron, you may have swapped the RX and TX lines: try reversing them.

Mounting

There are many ways to mount your Electron and its antenna to your drone. Here are a few photos of how I mounted the Electron on an F450 quadcopter for testing:

Running

Once flashed, your Electron should begin running mavleash right away, receiving mavlink data from your autopilot and forwarding a CSV summary to the Particle cloud.

The included /web/mavleash.html file provides an example of monitoring the status of your drone from the data available in the cloud using a simple web page with javascript.
To use it, you'll need to obtain your Electron's device ID and authorization token from the Particle.io site and populate those fields in the HTML file. This file is for test purposes only: be careful to never publish your authorization token.

In addition, you can use IFTTT.com (if this then that) to pull Particle.io events into other web services. I've setup an example IFTTT recipe that will pull particle event data (I use the 'statecsv' event mavleash generates) into a Google Drive spreadsheet: Each time mavleash generates a statecsv event, this recipe will add a row to the spreadsheet. This is handy for recording your flights.

You can setup a similar IFTTT recipe for tracking your flight time: mavleash also publishes the 'LANDED_STATE' event when your drone takes off (IN_AIR) or lands (ON_GROUND).

The sample mavleash HTML file provides a few command buttons:

RTL: Tells the drone to return to where it was launched (may work for some drones)
Land: This sends a landing command to your drone.
Takeoff: Tells the drone to takeoff (assuming it already has a mission and is in auto mode)
Reset: Tells the Electron board itself to reset

Be aware that different drones support different mavlink commands, and not all drones will react to these commands in exactly the same way. Test your vehicle in a safe venue before relying on mavleash to recover your drone if it flies away.

You can use something like Coda for iOS to load the mavlink HTML file locally on your phone and view live updates from your Electron.

Follow the directions from Particle.io if you wish to create a full-blown mobile app or website that monitors your device's location.

Next Steps

Some folks may wish to run both mavleash as well as a more traditional telemetry radio such as the SiK 915MHz/433MHz, or monitor their mavlink telemetry using MinimOSD.

You can readily split the output line (RX) of the autopilot mavlink port and supply it to multiple readers (SiK, MinimOSD, and Electron). This will provide you with a telemetry stream from the autopilot. You can configure the wiring so that one of the radios can write commands back to the autopilot's input pin. For example you could use the MAVBoard Lite

However, if you wish to send commands to the autopilot from multiple sources, this is more tricky. One option would be to use a digital multiplexer (eg NC7SZ157P6X) to switch between, say, the SiK and the Electron. You could output a mux control signal from one of the Electron's digital output pins so that when the Electron is sending commands, it owns the autopilot's input pin.

devbharat/mavleash