This is a bit of a proof of concept project. The parts have arrived so now it’s a ongoing project.
What’s the plan – A simple flight controller for fixed wing RC
The plan is to come up with a simple flight controller that can act as a safety backup in case of loss of RC control. It must stabilize the model and fly it back to the original launch location and loiter overhead until control is regained or the battery/fuel runs out. It must be reasonably priced and easy enough to use by anyone with minimal computer skills.
What are the options
Sure, there are plenty of existing flight controllers, but currently they all require extensive computer and other skills to configure and operate. Anyone who thinks they are easy to use has already spent many tens (probably hundreds) of hours coming up to speed.
It does not need advanced features, telemetry, data logging, 25 flight modes or waypoints.
Why Use Multiwii
This plan uses readily available hardware and the Multiwii Firmware (the programing that makes it work). Why Multiwii? Because it’s well established, well featured and works quite well. It is mainly a multirotor controller but has some options for fixed wing. For multirotor use development of Multiwii has slowed as the community is moving on to more powerful systems. But for this application we need something that works and is stable; we don’t need cutting edge performance and the latest features.
There will always be newer hardware and the latest firmware, but this needs to be stable and not always changing.
Computer skills required
Being open source and based on standard hardware means that you probably cannot buy it pre-loaded and ready to go.
You will need to install Arduino (here) on your computer and be able to plug the flight controller board in to your computer. I’ll explain this later.
The Arduino project that makes it work is a simple download. There will be a few lines to edit in a text file depending on your model; I may simplify this or just provide a few pre-configured options.
One of the biggest complexity problems with existing open source flight controllers is the complexity of working out what is required, where to get it from and what to do with it once you have it. Keeping it simple and all on one web page, files and documentation, should eliminate the confusion.
Bluetooth and the Android App
This is a handy way to adjust and monitor and confirm it’s working. You do need a Android phone or tablet with Bluetooth (they all have now).
The App I use is called MultiWii EZ-GUI, here. The basic version is free but for a few maybe $15 you get extra useful features.
Even if you don’t change the configuration, the APP lets you confirm that your model is working correctly and ready to fly.
The parts required
You can get these from a number of suppliers including Ebay and Hobbyking. I went to Ebay, as HK was out of stock of one item. There are differences between the various boards but for a simplified application like this any of them will do.
Hobbyking/Hextronic copy a lot of these boards and change the version numbers. I think a Hobbyking V2 is actually a Crius V1.1 and the Crius V2 includes data logging memory but Hobbyking don’t sell this one. I recommend buying the Legit Crius boards. I’ve found that some Hobbyking/Hextronic copies of flight controller and other boards are older versions, buggy and lacking important documentation when it comes time to sort out any problems that crop up.
There is a version 2 (V2) of this board, but V1 works fine for this application and is a bit cheaper. V2 adds data logging memory. This board is a bit overkill for the application, but it’s reasonably priced, easy to use with USB and the connectors already fitted, and has good sensors on-board. There is also a plastic case available that makes it easier to protect and mount.
GPS modules vary a lot in price and the ultimate performance is not required here. Most GPS modules will provide NMEA data by default and will work. Cheap is OK.
From Ebay, NZ$12, free shipping
The default baud rate for this module is 9600 baud. This should be changed to 115200. This can be done with a FTDI USB adapter (or cheaper equivalent) and the Arduino serial-monitor (tools menu). Connect the BT module to the FTDI adapter, power and RX-TX and TX-RX. Plug the USB into the computer. The LED on the BT module should be flashing. Select the serial-port (tools menu); the one that most recently appeared. In the serial-monitor, bottom left, select 9600 baud and “no line ending” (this is important). You can enter AT commands in the top line, one at a time, and press enter. The response appears in the main window below.
The default baud rate in Multwii is 115200. This can be changed within the Multiwii code, but is best left at 115200 baud.
For basic use you can ignore this and following sections.
Updated as progress allows.
This section is for reference and for anyone wanting to go further into how Multiwii works and how the to use the configuration apps and Arduino.
What is Multiwii? it’s an Adruino project or sketch in Arduino speak.
What is Arduino? – it’s a PC based tool (programming system) for some Atmel micro-controllers.
Installing Arduino on your PC
This depends on your PC. I use Linux (Kubntu), but most will be using Windows. For windows your best bet is to follow the instructions on the Arduino web site. It’s supposed to be simple to follow as Arduino is popular with beginners.
Download and install the Multiwii Sketch
You can get the sketch from this site (below) or to check for the latest version go to the Google code page: here.
Reference and Links:
Other information and Links.
Original Multiwii project site here.
Miltiwii Google Code: project code home and downloads and wiki documentation.
Hobbyking AIO flight controller here. Some info under files, but confusing.
RC Groups Crius AIO thread here. A long thread; dates from 2012 to current time.
How to setup a Multiwii Airplane: Patrik Emilsson blog.+ additional information.