For a more structured view, go to Wiki.

Flying Pi is a project for piloting a Raspberry Pi Zero W on a LARIX drone with a smartphone.

• Change SSID limitations
• Connect to a network
• Choose selection mode
• Pilot the drone
• Modify the joystick

All smartphone app related files can be found under Dronection. There you can find Android and iOS versions of the app, either using WiFi or Bluetooth (Android only).

The folder RPI contains files related to the Raspberry Pi:

• Python scripts
• Configuration files

In the XMC folder are all files stored, that are necessary for the bidirectional communication between Raspberry Pi and XMC.

WiFiDronection has two main functionalities:

• Piloting a LARIX drone with a Raspberry Pi Zero W on it.
• Visualizing data which was sent by the LARIX drone during a flight.

In MainActivity.cs the android device searches automatically for a matching WiFi network. Only networks with a SSID including Rasp and/or Pi (no matter if upper- or lowercase) can be found. If you want to change this limitation, you have to edit the following line in RefreshWiFiList():

IEnumerable<ScanResult> results = wifiList.Where(w => w.Ssid.ToUpper().Contains("RASP") || w.Ssid.ToUpper().Contains("PI"));

You can replace an exisiting string or add a new one by writing || w.Ssid.ToUpper().Contains("WHATEVER"). If there is no matching network, you can't go on to the Controller.

If you press the Connect button you will be asked to enter the password. The default password is 87654321 (or 00000000), but it depends on the hostapd-configuration of the Raspberry Pi. If you are already connected to the network, you can just press the OK button and ignore the dialog and a new socket connection (SocketConnection.cs) to 172.24.1.1:5050 will be established.

On most Android devices a popup-dialog will appear while connecting to the Raspberry PI, which will say, "The Internet is unavaiable with "..." (Picture below). This Popup is not created by the Donection application, but by the OS and just shows, that you have no Internet access over the Raspberry Pi, because it is configured as an Access Point between the mobile phone and the XMC-Drone.

After connecting to the network, you will be forwarded to ControllerActivity.cs. Before using the smartphone as a controller, you have to choose between two selection modes by clicking either on the radio button or the image.

You can't change the controlling mode during a flight.

After pressing Start, a view with two joysticks, which are responsible for controlling the drone, and the socket connection will open. This process takes place in ControllerActivity.cs and ControllerView.cs. At the top of the screen you can make following settings:

• Activate/deactivate altitude control
• Adjust trims for yaw, pitch and roll

If altitude control is deactivated, the button has the background color blue and you can control the drone manually. A click on Altitude Control turns the background color to red and sets the speed to 50 % (although the joystick is not at 50 %). When altitude control is activated, you can just control yaw, pitch and roll while speed is regulated by the drone itself.

Trims can be adjusted by choosing the radio button and moving the seekbar. Just for explanation:

• Plus Yaw: Turn right
• Minus Yaw: Turn left
• Plus Pitch: Move forward
• Minus Pitch: Move backward
• Plus roll: Move right
• Minus roll: Move left

If you want to change the minimum and maximum trim value, you have to edit mMinTrim in ControllerActivity.cs and android:max of the seekbar in ControllerLayout.axml.

Currently, the sensibility of the joysticks is very low. You can make it higher by giving mMult, mMultRudder and/or mMultThrottle a higher value in Joystick.cs.

A Raspberry Pi Zero W can be configured as an access point providing a wireless LAN with the following steps. If you are not root, you have to give your user rights with this command:

sudo chmod 777 <dir_or_file>

Download hostapd and dnsmasq:

sudo apt-get update
sudo apt-get install dnsmasq hostapd

Replace the wlan0 section in /etc/network/interfaces with the following text:

allow-hotplug wlan0  
iface wlan0 inet static  
    address 172.24.1.1
    netmask 255.255.255.0
    network 172.24.1.0
    broadcast 172.24.1.255

Restart dhcpcd with sudo service dhcpcd restart and reload the configuration for wlan0 with

sudo ifdown wlan0
sudo ifup wlan0

Create a new file with sudo nano /etc/hostapd/hostapd.conf with the following content:

# Set the name of the configured wifi interface
interface=wlan0

# Use the nl80211 driver with the brcmfmac driver
driver=nl80211

# Set the SSID of the network
ssid=RaspberryWiFi

# Use the 2.4GHz band
hw_mode=g

# Use channel 6
channel=6

# Enable 802.11n
ieee80211n=1

# Enable WMM
wmm_enabled=1

# Enable 40MHz channels with 20ns guard interval
ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]

# Accept all MAC addresses
macaddr_acl=0

# Use WPA authentication
auth_algs=1

# Require clients to know the network name
ignore_broadcast_ssid=0

# Use WPA2
wpa=2

# Use a pre-shared key
wpa_key_mgmt=WPA-PSK

# Set network passphrase
wpa_passphrase=raspberry

# Use AES instead of TKIP
rsn_pairwise=CCMP

Edit the file /etc/default/hostapd and change the line #DAEMON_CONF="" to

DAEMON_CONF="/etc/hostapd/hostapd.conf"

Open the file /etc/dnsmasq.conf and add the following content:

# Use interface wlan0
interface=wlan0

# Explicitly specify the address to listen on
listen-address=172.24.1.1

# Bind to the interface to make sure we aren't sending things elsewhere
bind-interfaces

# Forward DNS requests to Google DNS
server=8.8.8.8

# Don't forward short names
domain-needed

# Never forward addresses in the non-routed address spaces
bogus-priv

# Assign IP addresses between 172.24.1.50 and 172.24.1.150 with a 12 hour lease time
dhcp-range=172.24.1.50,172.24.1.150,12h

The last step is to restart the services:

sudo service hostapd start
sudo service dnsmasq start

Thanks to Phil Martin for this tutorial!

To receive and send data between the XMC and Raspberry Pi Zero W, some configuration must be done on the RPI. It's a good idea to make a backup of your SD card before configuring. Reboots during the steps are also recommended. Again, if you are not root, you have to give your user rights with this command:

sudo chmod 777 <dir_or_file>

Add following content to the bottom of the file /boot/config.txt:

gpu_mem=128
enable_uart=1
dtoverlay=w1-gpio
force_turbo=1

As the next step, search the following line in '/boot/cmdline.txt':

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

Delete console=serial0,115200 and the whole content after 'rootwait'.

Type the command sudo raspi-config, choose Interface options -> Serial and then disable shell and enable interface.

Open the file /lib/systemd/system/hciuart.serviceand replace everything with:

[Unit]
Description=Configure Bluetooth Modems connected by UART
ConditionPathIsDirectory=/proc/device-tree/soc/gpio@7e200000/bt_pins
Before=bluetooth.service
After=dev-ttyS0.device

[Service]
Type=forking
ExecStart=/usr/bin/hciattach /dev/ttyS0 bcm43xx 921600 noflow -

[Install]
WantedBy=multi-user.target

Create a file fhem in /etc/init.d/ and add sleep 10 as content.

Thanks to FHEM Wiki for this tutorial!

The Python script main.py will be executed as a background process directly after the Raspberry Pi has booted. Its main function is to run other Python scripts on the Raspberry. At the time only rpi_socket.py functions are called, but it can be easily extented by adding a new Python script to the project folder /Desktop/FlyingPi/RPI/Wifi/'your script' and adding at the beginning of main.py from 'script filename' import 'class name' and initialize the object by calling object_name = class_name(). Of course you can also write you code in the main.py script, but it is highly recommended to use other scripts and import them.

The script rpi_socket.py handles the full duplex data exchange between the Android or IOS device to the Raspberry Pi via Wifi connection and goes further to the XMC-Drone via Serial port.