edrone AR drone control library for Erlang

edrone_client.erl implements the standard commands used to control the standard AR drone 2.0 (may work with version 1.0 as well)

In priv directory there is also an Erlang that can be installed on the AR drone 2.0 (not 1.0) it self.

Install Erlang procedure

After attaching the wifi network announced by the drone, start with transfer the erlang archive and the libutil file to the drone, any user (like root) and no password is passed to ftp.

ftp 192.168.1.1
>put arm-unknown-linux-gnueabi-erl.tgz
>put libutil-2.13.so

Then telnet to the target

telnet 192.168.1.1

You will find the archive placed in /data/video, now unpack and install erlang

cd /date/video
tar xzf arm-unknown-linux-gnueabi-erl.tgz
rm  arm-unknown-linux-gnueabi-erl.tgz
mv /data/video/arm-unknown-linux-gnueabi-erl /data/erlang

and the shared object libutil-2.13.so.

mv /data/video/libutil-2.13.so /lib
cd /lib
ln -s libutil-2.13.so libutil.so.1

Install and check for a prompt

cd /data/erlang 
./Install -minimal /data/erlang
/data/erlang/bin/erl

Copy the additional erlang libraries to the drone: sh transfer-libs.sh

This command will ftp edrone.tgz, gpio.tgz, i2c.tgz and uart.tgz to the edrone (192.168.1.1), and then install these packages under /data/erlang/lib

Loading code with distributed erlang

Instead of transfering libraries and files to the drone every time a beam files is changed the erl_prim_loader can be told to told from the development machin instead.

Erlang on the drone is then started like:

erl -loader inet -id drone -hosts 192.168.1.2

To make the drone node a distribute node then give the following arguments

-sname drone -setcookie <cookie>

On the development a node with a bootserver must have been started

erl -kernel start_boot_server true boot_server_slaves '[{192,168,1,1}]'

The boot server node may also be a distributed node by giving the following argument to the command line:

-sname devnode -setcookie <cookie>

Note the argument to boot_server_slaves, for some reason the manual is wrong here and this is the only accepted format. is any string, like a password. This erlang system will list on a tcp port number 555 and and udp port 546.

The flying bit

Connect a Logitech Extreme 3D Pro joystick to a PC connected to the AR Drone WiFi access point.

On the PC, start erlang and fire up the edrone_pilot app:

erl 
application:start(inpevt).
application:start(edrone_pilot).

Telnet to the AR Drone
```
telnet 192.168.1.1
```

Kill the original AR Drone flight control software.

ps | grep program.elf | head -n 1 - | cut -c 1-5 | xargs kill

Start an erlang prompt on the Drone:
```
/data/erlang/bin/erl
```

Start the necessary apps on the drone On the erlang command prompt, enter:

application:start(uart).
application:start(gpio). 
application:start(edrone). 
edrone_control:flat_trim(). 
edrone_control:enable().

Joystick controls

Stick forward
Dip the nose of the drone, making it move forward.
Stick backward
Raise the nose of the drone, making it move backward.
Stick right
Raise the left side of the drone, making it move to its left.
Stick left
Raise the right side of the drone, making it move to its right.
Rotate stick left
Make the drone rotate anti clockwise.
Rotate stick right
Make the drone rotate clockwise.
Throttle (base of the joystick)
Throttles the motors between off and max.
Fire button
Press and hold to disable throttle control and lock altitude at the current level.
Thumb button (left side of stick)
Activate a newly uploaded edrone_control.beam file (through edrone_upgrade.erl).

Demo script (to be simplified)

Edit the edrone_control.erl file to introduce glitch
Set the HAVE_GLITCH value in edrone_control.erl, line 58, to 0.
Make sure that the development PC is connected to AR Drone WiFi network
To avoid interferrence with wired networks that uses the 192.168.1 subnet, disconnect any ethernet cable from the PC.
Compile and upload new file
Move to edrone home directory, and run the following commands
```
rebar compile
cd priv
sh transfer-libs.sh
```
The new software image, with a glitch, is now installed on the drone.
Start drone pilot software on the development PC
See previous chapter for start instructions.
Start drone software on AR Drone
See previous chapter for start instructions. Ensure that the Drone is located in an open area, with its nose (camera) pointing away from you. The glitch may cause temporary, low-level operation of the motors while the drone is still on the ground.
Remove the glitch fromn edrone_control.erl
Set the HAVE_GLITCH value in edrone_control.erl, line 58, to -1.
Recompile and transfer the fixed software to the drone
Repeat step 3 above to compile and transfer the image.
Raise the drone to 1 meters height
Apply throttle until the desired height is reached. Control pitch, roll and yaw roll using the the joystick. The glitch will cut out the motors at irregular intervals, but the flight control system will compensate.
Press and hold fire button to lock altitude
Throttle will be deactivated for as long that you hold the button. The locked altitude will make it easier to see the glitch and its effects on the drone's flight
Press the thumb button to upgrade software
The glitch will disappear and flight will be stabilized.
Release the fire button to disengage altitude lock
Land the drone
Throttle back until the drone has landed.

borodark / edrone