fcs-platform

This is the platform support for my Raspberry Pi-based flight controller.

Hardware:

Raspberry Pi Model B
Pololu Micro Maestro serial servo controller
CH Robotics ~~UM-6 and Pololu GPS~~ GP-9 via Pololu USB-to-serial adapter

TODO

Get CMake to export a statically linkable library
Delete main.c
Get sending commands to the IMU to work properly
Get IMU health report to be more meaningful (ensure has GPS lock at least)
Write some kind of tests

DONE

Add Rpi tools repository as a submodule rather than cloning it into toolchain Docker image
Connect to and read from IMU
Create C API for driving servos
Create C API for reading IMU
Get Rpi to wiggle a servo using Maestro example bash script
Ship source code from laptop to Rpi
Set up cross compiler
Cross-compile, deploy binary, and run on Rpi in one command
Get Rpi to wiggle a servo using Maestro example C code
Bring platform/src to root
Move src/maestro to src/platform/servo_controller

MISTAKES

~~Get Docker on Rpi~~ dumb idea
~~Build minimal development container with compiler~~ needed a cross-compiler instead
~~Compile and run source code within development container~~ run a binary on the Rpi natively

Setup

Put Linux on Rpi

Install Arch Linux on an SD card. Make sure to resize the partition to take up the available space. (Use fdisk to rewrite the partition table and resize2fs to do the actual resizing. Google it.)

Put Docker on your laptop

Make sure you've got Docker on your laptop and your docker command is set up to talk to a Docker daemon. On OS X, I use boot2docker. Ensure boot2docker is up and running;

$ boot2docker up

Use the cross-compiler

The core build script builds a Docker container with a compiler toolchain that targets the Rpi and then invokes compiler.

$ ./build.sh

The first time you run this it will take a while to build the docker image. Successive runs will be faster.

Run the program

We scp the resulting binary onto the Rpi (make sure your public key is on the Rpi so you don't have to type your password) and then run it.

./deploy.sh root@192.168.2.200

Congratulations, you're hacking!

For some reason the program doesn’t always die on the Pi when you expect it to. You might need to:

$ ssh root@192.168.2.200 killall fcs-platform

Notes about connecting to the Pi on OS X

I wanted to be able to work on the Pi without having to plug it into a router, rather, I wanted to plug it into my Macbook Air directly via ethernet and the Thunderbolt ethernet adapter. OS X Internet Sharing was being a contrarian as I attempted to do this. After much wailing and gnashing of teeth I arrived at this process:

Disable Internet Sharing
Delete the following files: /Library/Preferences/SystemConfiguration/com.apple.nat.plist /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist /Library/Preferences/SystemConfiguration/com.apple.network.identification.plist /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist
Reboot.
Re-enable Internet Sharing.
It worked!

Create /etc/bootptab to cause the Pi to always get the same IP address:

%%
raspberry-pi 1 b8:27:eb:c:45:4f 192.168.2.200

Do not go about trying to hand-edit /etc/bootpd.plist, because the Internet Sharing dialog in System Preferences is meant to stomp on that file. Tailing /var/log/system.log was instructive.

I also modified /System/Library/LaunchDaemons/bootps.plist to add the -dv flag so bootpd would emit more interesting log messages:

...
<key>ProgramArguments</key>
<array>
    <string>/usr/libexec/bootpd</string>
    <string>-dv</string>
</array>
....

Notes about talking to the GPS

TIL that this is useful for cat-ing the raw output from the GPS:

$ stty -F /dev/ttyUSB0 57600 raw

bvanderveen/fcs-platform