The Drone API project has come about as a result of wanting to offer REST APIs that can control a drone. By exposing the means to control the drone via REST it becomes possible for people for people to build solutions with just about any technology of choice. From simple scripts using CURL to clever web apps.
The development of the platform wraps and extends the Gobot framework so eventually the framework could be utilized to provide APIs on any of the Gobot supported drones. Today the focus is entirely on the use of the Parrot Bebop 2 drone
An API First approach - as a result the API Blueprint has been developed and is periodically committed to this GitHub repo. By adopting an API 1st approach it means that anyone can start building against the APIs whilst we build out the layer around Gobot
The API Blueprint can be seen here.
One of the important things to understand is the axis that impact flight:
The API layer is obviously also written in Go. Go is a well supported and mature language with strong typing like Java, but has characteristics of C by being explicit about the use of pointers, there is no class inheritance, data structures are defined using struc definitions and methods can be part of an interface, as a result polymorphic behaviour is easy to achieve. Go also offers the more relaxed approach to the need for semicolons, type definitions you see in Groovy.
Go also offers the portability of Java. So this functionality can be run on any platform supporting Go which includes Windows, Linux OS X.
The implementation completely wraps and abstracts the Gobot framework so no understanding of Gobot is required. Masny of the URIs are very simple and can be realized using a browser.
The Web server / URI handling has been implemented using Gorrilla Mux.
In addition to driving a real drone. It is possible to also cooperate the backend with a simulation display. Each of the action calls are forwarded onto a JET Application called drone-dash which will display messages of what the drone is being asked to do, and provide a visual representation. Drone-dash is available here.
To get started and use this framework you need to:
- Install Go - instructions here
- Retrieve Gorilla/Mux - instructions here 2b. Retrieve Gorilla/Websocket - here
- Download this library here
- Compile everything using the Go build command
- Start up the server - this is down the filesystem naming, but the preceding steps should give a binary executable
Whilst we have worked hard to ensure the code is self documenting the following provides details on which files do what so you can start to traverse the code, or add to it without compromising the abstractions and code structure ...
there are two packages, main which contains the REST handling layer and dronecore which provides the wrapping layer.
- webhandler.go this includes the declarations for the Gorrilla Multiplexer (MUX) providing the declarations for the handlers. The URIs defined are presented in a manner that makes it as close as possible to the Blueprint representation. additionally the URIs are declared with both a trailing / as it impacts the MUX ability to handle the call. We have also included alias paths for example yaw and rotation
- performActions.go The handler functions have been grouped together in the main tier. All the handler files incorporate the task of taking the REST calls and translate the web call to the relevant calls in the dronecore layer. performactions takes the actions like takeoff, land etc. The ohers are performEmergency which takes an Emergency Stop which then goes through all the known drones and lands and stops them regardless of what is happening. PerformRegistrations takes the registration call and locates drone(s) or creates dummy ones and registers them performSiompleNavigations contains the change yaw, gaz etc
- dronelogging makes use of the basic logging framework to handle simple Log4J style logging and exposes 4 objects Trace, Info, Warning, Fatal -- these entities have no linkage to the DroneDash feature
- droneobj.go This provides the means to wrap the gobot library and provides the primary struc which holds, a number of key elements relating to a drone, this includes the driver and connection object, plus a handle to a reporter object which provides the means to record what the drone is being asked to perform
- drone-services.go This provides the handler for non drone instance specific logic, such as translating a URI to get the name of the drone and locating the cached drone object.
- droneReport.go
- droneactions.go
To control the drone it first has to be registered through the RegisterDrone API call - then any command can be sent, but IF the drone is in the wrong state a BadRequest response will be provided. APIs not yet implemented will return NotImplemented