PiQuadcopter

Websocket and MultiWii serial code to control a quadcopter, running on a Raspberry Pi

Note: All development and testing was done on a RaspberryPi 2 B+, in 2016. So be warned, things might not work exactly the same now.

Overview of all the tech

• The first thing to do is to create a hosted Wi-Fi network. To accomplish this we use isc-dhcp-server and hostapd
  • isc-dhcp-server serves as the DHCP server for our Wi-Fi network
  • hostapd serves as access point management, essentially making a Wi-Fi card into a router
• Now for communication with our MultiWii device. I have a C library with the MSP protocol, and I use a backbone library libserialport
  • libserialport is downloaded from their git repository, and installed
  • cMultiWii, my MSP implementation is downloaded from the git repository. This will be compiled later
• Websocket communication is needed next. I use the websocketpp library, implemented in this repo.
  • websocketpp is not installed. It is a header-only library (.hpp), and is compiled each time (with the intention of improving performance)
• Compiling websocket.cpp in this repo will build the executable that will recieve commands from a remote control, and then relay them to the MultiWii. It compiles the websocketpp library which takes along time, and the cMultiWii library which is quick to compile.

Instructions to set up your Pi with all of the software it needs:

• Download/clone this repo
• Run setup_pi_software.sh, which will install libserialport, isc-dhcp-server, hostapd, and download cMultiWii, websocketpp. It will also compile the websocket server
  • You need to check to see if your MultiWii is /dev/ttyUSB0. Check the troubleshooting section for more information
• Since your network configuration and device might be different, your /etc/network/interfaces, /etc/default/isc-dhcp-server, and /etc/dhcp/dhcpd.conf files are not automatically modified.
• Add the following configuration to your /etc/network/interfaces file in order for hostapd to work. Also, remove any reference to wpa_supplicant, as it causes issues with hostapd

allow-hotplug wlan0
iface wlan0 inet static
  address 192.168.10.1
  netmask 255.255.255.0
  gateway 192.168.10.1

• Add the following configuration to your /etc/default/isc-dhcp-server file in order for isc-dhcp-server to know what device to use

INTERFACES="wlan0"

• Add the following configuration to your /etc/dhcp/dhcpd.conf file in order for isc-dhcp-server to know what subnet to use

subnet 192.168.10.0 netmask 255.255.255.0 {
    range 192.168.10.1 192.168.10.30;
}

• You need to ensure wlan0 and hostapd.conf are correct. check the troubleshooting seciton for more information

Running the program and automatic startup

• I would suggest a reboot after all of the installation process
• To start up the hosted network and the websocket, run sudo ./piquadserver.sh
• To schedule everything to start up automatically on boot, edit /etc/rc.local with something like...
  • cd /home/path/to/piquad
  • ./piquadserver.sh &.
  • rc.local is called automatically on startup.
  • Check troubleshooting for more help

Troubleshooting

• To find your wireless interface, run ifconfig
• To find your USB device, run dmesg | grep ttyUSB and look for what number it is
  • Once you find your device, you will need to edit line 4 of configure_port.c within cMultiWii to reflect the proper device. You will have to recompile.
• If your wireless interface is not wlan0, then you will have to change it in your interfaces file, and in hostapd.conf
• Check /etc/hostapd/hostapd.conf for hostapd configurations, and make sure they match your interfaces configuration
• If hostapd is throwing errors similar to: n180211: Could not configure driver mode ... then you probably need to kill the instance of hostapd already running.
  • Run ps -A to view all active processes
  • Find the process ID number for hostapd
  • sudo kill <process ID> will kill hostapd and hopefully resolve the issue
• If there are any problems with isc-dhcp-server, try running sudo journalctl -u isc-dhcp-server.service to look for errors
• If you need to recompile at any time, just run make at the top level of this repository