From 2211c7687dde28f4cd6460a5bc409917b1d0e48e Mon Sep 17 00:00:00 2001 From: Jakob Odersky Date: Tue, 24 May 2016 22:22:04 -0700 Subject: Add presentation --- presentation/index.html | 504 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 504 insertions(+) create mode 100644 presentation/index.html (limited to 'presentation/index.html') diff --git a/presentation/index.html b/presentation/index.html new file mode 100644 index 0000000..b4679ea --- /dev/null +++ b/presentation/index.html @@ -0,0 +1,504 @@ + + + + + + Not Your Dad's Scala: Flying Objects and Proactive Streams + + + + + + + + + + + + + + + + + + + + + + + + + +
+ + +
+ +
+

Not Your Dad's Scala: Flying Objects and Proactive Streams

+
Jakob Odersky
+
+ @jodersky +
+

+

April 18, 2016

+

+
+ + +
+

Or,
Navigating a Drone with Scala

+
+
+

Initial Idea

+
    +
  • Build a quadrotor
    • +
  • From scratch +
      +
    • hardware
      • +
    • software
      • +
    • +
  • Control with a joystick, no remote
    • +
  • ⇒ Project Condor
    • +
+
+
+

Two Parts

+
    +
  1. The Quadrotor
    2. +
  2. The Base Station
    3. +
+
+
+

System Overview

+
+overview
overview
+
+
+
+

1. The Quadrotor

+
+

(the flying object)
No Scala Here

+

Move on to the Scala parts →

+

See backstory ↓

+
+
+

Frame

+
+Structure
Structure
+
+
+
+

Frame

+
+Unit
Unit
+
+
+
+

Electronics

+
+Trifle Board
Trifle Board
+
+
+
+

Flight Stack

+
    +
  • And then I found PX4, exactly what I was trying to build.
    • +
+
+
+

Alternative: PX4

+
    +
  • Open Source Software
    • +
  • Developed by Computer Vision and Geometry Group, ETHZ
    • +
  • Uses open, wide-spread protocol MAVLink
    • +
  • Runs on free RTOS NuttX, available for AVR, ARM and more.
    • +
+
+
+

Pixhawk Hardware

+
    +
  • Developed by the same group
    • +
  • Expensive
    • +
  • I already have a microcontroller and all sensors
    • +
+
+Pixhawk
Pixhawk
+
+
+
+

NuttX (beginning 2015)

+
    +
  • Our board uses the Teensy 3.1: +
      +
    • ARM Cortex M4
      • +
    • Freescale Kinetis K20 family
      • +
    • +
  • NuttX (beginning 2015) has support for K40 family
    • +
+
+
+

Let's port it!

+
    +
  • Subtle differences in processor families, K20 != K40
    • +
  • I was never much involved with kernel development beforehand
    • +
  • Debugging microcontrollers is no fun +
      +
    • (without JTAG or other fancy equipment)
      • +
    • +
+
+
+

Fast-forward 2 months

+
+
+

Get the Pixhawk and move on

+
+
+
+

Quadrotor Take-Away:

+
    +
  • A lot of work has gone into existing hardware platforms
    • +
  • ⇒ Use existing Pixhawk controller
    • +
+
+Pixhawk
Pixhawk
+
+
+
+

2. The Base Station

+
    +
  • Control drone with joystick/gamepad
    • +
  • Display live flight information +
      +
    • "virtual cockpit"
      • +
    • +
  • Underlying process: (proactive) message streaming
    • +
+
+ + + + +
+

Mavigator

+ + + + + + + + + + + + + + + + + + + + + + + + + +
Requirementadd ScalaArea
Modern, portable UIScala.jsfrontend
Web serverAkka Httpbackend
Message streamingAkka Streamsbackend
+
+
+

Live Demo

+
+

Alternatives

+ +
+
+
+

Frontend: Scala.js

+
    +
  • A JavaScript backend to the Scala compiler. +
      +
    • All the goodies from Scala: type safety, collections, etc
      • +
    • Outputs plain JavaScript
      • +
    • Can interface with plain JavaScript
      • +
    • +
  • Developed at EPFL by Sebastien Doeraene
    • +
  • Still in 0.x but totally usable!
    • +
+
+
+

Frontend: Design

+
    +
  • One-page applications
    • +
  • Static scaffolding with Twirl (Play! templates)
    • +
  • Common launcher for all applications
    • +
  • Extensible "cake" pattern: +
      +
    • Providing web page environment
      • +
    • Reading messages
      • +
    • Displaying instruments
      • +
    • Laying out elements
      • +
    • +
+
+
+

Backend: Akka Streams

+
    +
  • Compatible with Reactive Streams +
    • +
  • "Natural" Streaming API
    • +
+
+
+

Streams as Graphs

+
+overview
overview
+
+
+
+

Streams in Code

+
+ +
+
//Simple source
+val src: Source[Int, _] = Source.tick[Int](100millis, 100millis, 1)
+
+//Nested source
+val inc: Source[Int, _] = src.scan(0)(_+_)
+
+//A discrete flow
+val flow = Flow[Int].map(_*2)
+
+//Simple sink
+val sink = Sink.foreach(println)
+
+//Print all even numbers, ad infinitum
+(inc via flow to sink).run()
+
+
+
+

More Streams

+
    +
  • Arbitrary graphs
    • +
  • Feedback loops
    • +
  • Materialization
    • +
  • Much more...
    • +
+

http://akka.io

+
+
+

Backend: Conceptual Model

+
+Conceptual stream model
Conceptual stream model
+
+
+
+

Backend: Actual Model

+
+Actual stream model
Actual stream model
+
+
+
+

Serial Backend

+
Serial().watch(Set("/dev/ttyUSB0")).runForeach{ port =>
+
+  //replace backend on connection
+  val multiplexer: Flow[Bytes, Bytes, NotUsed] = setBackend()
+
+  //open actual connection to drone
+  val uav: Flow[Bytes, Bytes, NotUsed] =
+    Serial().open(port, serialSettings)
+
+  (uav join multiplexer).run()
+}
+ +
+
+

Web Sockets

+
path("/mavlink") {
+  get {
+    val fromWebSocket = Flow[Message].collect{
+      case BinaryMessage.Strict(data) => data
+    }
+
+    val toWebSocket = Flow[Bytes].map{bytes =>
+      BinaryMessage(bytes)
+    }
+
+    //request connection to multiplexer
+    val backend: Flow[Bytes, Bytes, NotUsed] = Uav().connect()
+
+    handleWebSocketMessages(fromWebSocket via backend via toWebSocket)
+  }
+}
+
    +
  • Akka Route DSL
    • +
  • Graph is run by Akka Http
    • +
+
+ +
+

Demo: Do a Barrel Roll

+
    +
  • Define "unstable" message
    • +
  • Add extra UI element to notify user
    • +
  • Inject attitude messages
    • +
+
+
+

Message

+

Add to dialect definition:

+
<message id="150" name="STABILITY">
+    <description>Stability issues</description>
+    <field type="uint8_t" name="stable">Is it stable?</field>
+</message>
+
+
+

New UI element

+
    +
  • Danger indicator
    • +
  • Illuminates on stability issues
    • +
+
+
+

Barrel Roll: Injection

+
+overview
overview
+
+
+
+

Live Demo

+
+

Alternatives

+
    +
  • git checkout demo1-before
    • +
  • git checkout demo1-after
    • +
+
+
+
+

References

+ +
+
+ + + + + + + + -- cgit v1.2.3