Building a Linux Powered Multi-copter from Scratch

Introduction

I purchased my first quadcopter about 6 years ago, back in the heyday of MultiWii. I flew it a few times, crashed it a few times, and it was fun for a little while, but my model lacked GPS, WiFi, and stabilized video, so it ended up sitting on a basement shelf for a few years.

Fast forward to fall 2017, where two things came together. One, I was able to get my hands on an Intel Aero RTF. This is a very powerful computing package on "wings." And two, the Beaglebone Blue came to my attention. It didn't take me long to come up a burning question...."I wonder if I can get the Beaglebone to do most of the stuff the Aero does?"

Let's find out!

Here is my syllabus for the next few blog posts. I'll try to match my normal development progression: get something working and then tweak it for performance.

1. Component Details
2. Initial Board Bring-up
3. Flight Control Software
4. Ground Tests
5. Mavlink Improvements
6. Boot Time Improvements

Stay tuned for Component Details...coming up after a short break.

Howto: Bluetooth GN/NAP on Beaglebone

This is an old article that I never published, but I'm making it available now, "as-is". Some of the instructions may be outdated, but I hope you find it helpful.

Recently I had the need to create a more secure wireless network connection. Bluetooth NAP came up as a viable solution, for a number of reasons:

• Short Range
• Fewer Sniffing/Hacking/War-driving tools
• Mobile device support (Android/IOS)

I'll detail some of the configuration challenges and pairing procedures to get it up and running.

Prerequisites

• Linux beaglebone 3.8.13-bone50 #1 SMP Tue May 13 13:24:52 UTC 2014 armv7l GNU/Linux
• Bluetooth USB Dongle: GBU521 (http://www.iogear.com/product/GBU521/)
• Powered USB Hub (IO Gear Bluetooth adapter will not work when directly plugged into Beaglebone)

Get Bluetooth up and running

Update servers/folders/file names:

sudo apt-get update

Bring installed packages up-to-date:

sudo apt-get upgrade

Install necessary packages:

sudo apt-get install bluez bluez-tools bridge-utils

Ensure Bluetooth is up and running by listing loaded Kernel modules:
debian@beaglebone:~$ lsmod

Module                  Size  Used by
rfcomm                 26769  10
bnep                    8909  2
g_multi                50407  2
libcomposite           15028  1 g_multi
btusb                  10339  0
bluetooth             159258  24 bnep,btusb,rfcomm
rfkill                 16672  2 bluetooth
mt7601Usta            641118  0

Verify Bluetooth Stack

See if device is up via bluez:

debian@beaglebone:~$ hciconfig -a
hci0:   Type: BR/EDR  Bus: USB
        BD Address: 00:02:72:CC:B8:47  ACL MTU: 1021:8  SCO MTU: 64:1
        UP RUNNING PSCAN
        RX bytes:1351 acl:0 sco:0 events:60 errors:0
        TX bytes:1333 acl:0 sco:0 commands:60 errors:0
        Features: 0xbf 0xfe 0xcf 0xfe 0xdb 0xff 0x7b 0x87
        Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
        Link policy: RSWITCH SNIFF
        Link mode: SLAVE ACCEPT
        Name: 'beaglebone-0'
        Class: 0x420100
        Service Classes: Networking, Telephony
        Device Class: Computer, Uncategorized
        HCI Version: 4.0 (0x6)  Revision: 0x1000
        LMP Version: 4.0 (0x6)  Subversion: 0x220e
        Manufacturer: Broadcom Corporation (15)

Pair Beaglebone and Device

NOTE: Make sure you have a discoverable Bluetooth device turned on now... 

Test scanning:

debian@beaglebone:~$ hcitool scan
Scanning ...
        60:A4:4C:00:00:00       CGM Nexus 7

Configure local Bluetooth settings:

debian@beaglebone:~$ bluez-test-adapter name honeypot
debian@beaglebone:~$ bluez-test-adapter pairable on
debian@beaglebone:~$ bluez-test-adapter discoverable on
debian@beaglebone:~$ bluez-test-adapter discoverabletimeout 30

NOTE: After setting discoverable to on, you must scan for the beaglebone before the timeout. If you took too long, simple set discoverable to on again.

Pair the beaglebone to the other device

debian@beaglebone:~$ bluez-simple-agent
Agent registered
RequestConfirmation (/org/bluez/15561/hci0/dev_60_A4_4C_B7_C0_A2, 945453)
Confirm passkey (yes/no): yes

Press CTRL-C to quit simple agent....

Add the other device to the trusted list

debian@beaglebone:~$ bluez-test-device trusted 60:A4:4C:B7:C0:A2 yes

At this point the devices are paired, but no services are running on the Beaglebone.

Configure Services

Add NAP service to Beaglebone by editing bluez-nap-server:

debian@beaglebone:~$ sudo nano /usr/local/bin/bluez-nap-server

#!/usr/bin/python

import sys
import time
import dbus
from optparse import OptionParser, make_option

bus = dbus.SystemBus()

manager = dbus.Interface(bus.get_object("org.bluez", "/"), "org.bluez.Manager")

option_list = [
      make_option("-i", "--device", action="store", type="string", dest="dev_id"),
      ]
parser = OptionParser(option_list=option_list)

(options, args) = parser.parse_args()

if options.dev_id:
        adapter_path = manager.FindAdapter(options.dev_id)
else:
        adapter_path = manager.DefaultAdapter()

server = dbus.Interface(bus.get_object("org.bluez", adapter_path), "org.bluez.NetworkServer")

service = "nap"

if (len(args) < 1):
        bridge = "tether"
else:
        bridge = args[0]

server.Register(service, bridge)

print "Server for %s registered for %s" % (service, bridge)

while True:
        time.sleep(1000)

Make it an executable file:

debian@beaglebone:~$ sudo chmod a+x /usr/local/bin/bluez-nap-server

Start it at boot by creating/editing a service file:

debian@beaglebone:~$ sudo nano /etc/systemd/system/bluez-nap.service

[Unit]
Description=Bluetooth NAP Server
After=syslog.target

[Service]
Type=simple
ExecStart=/usr/local/bin/bluez-nap-server br0
WorkingDirectory=/home/debian

[Install]
WantedBy=multi-user.target

Enable the service:

debian@beaglebone:~$ sudo systemctl enable bluez-nap.service

Enable DHCP by modifying udhcpd config file:

debian@beaglebone:~$ sudo nano /etc/udhcpd.conf
start      169.254.7.2
end        169.254.7.2
interface  br0
max_leases 1
option subnet 255.255.255.252

Create Bluetooth Bridge interface (add to end of interface file, after usb0 definition):

debian@beaglebone:~$ sudo nano /etc/network/interfaces
# Bluetooth NAP interface
auto br0
iface br0 inet static
address 169.254.7.1
netmask 255.255.255.0
bridge_ports none
bridge_fd 5
bridge_stp no

Reset and restart services

debian@beaglebone:~$ sudo systemctl restart networking.service
debian@beaglebone:~$ sudo systemctl restart udhcpd.service
debian@beaglebone:~$ sudo systemctl restart bluez-nap.service

References

• http://notes.pitfall.org/ip-over-bluetooth-to-a-raspberry-pi.html
• http://www.hkepc.com/forum/viewthread.php?tid=1710030
• http://forum.doozan.com/read.php?2,2698
• https://viaforensics.com/articles-presentations/bluetooth-packet-capture-android.html
• https://bbs.archlinux.org/viewtopic.php?pid=1129449
• http://www.linux.com/learn/tutorials/346552-personal-area-networking-with-bluetooth
• https://github.com/Douglas6/pinaple
• http://www.raspberrypi.org/forums/viewtopic.php?t=36889&p=479992h

Howto: Build Octal Beaglebone Black Cluster

Compiling Qt is getting old. While my applications are not that big, I find myself building Qt from source more often that I would like. I have cross compiled Qt on an x86 Ubuntu machine, but getting the configuration script to properly detect all of the modules is time consuming.

My first idea was to get a few Beaglebones so that I could be building multiple versions at any given time. This worked well, but it still took 20+ hours to get a testable output. If only there was a way to get these Beaglebones to help each other out......ah, but there is!

Enter distcc. Distcc is nice in that it is simply a wrapper around your existing build commands. This means it is easy to setup and use. Distcc works by inserting itself between the make script and the compiler (gcc or g++), which it accomplishes through the standard CC and CXX command line options available through make. By redirecting gcc and g++ commands through distcc, you can get a parallel build across machines using the normal make -j option.

Overview

• Configure hardware
• Install image
• Install packages
• Configure Main build client
• Configure compile hosts
• Run

Hardware

• 8 Beaglebone Blacks (2 Rev. A6A, 1 Rev. B, 3 Rev. C, 2 Element 14 Rev. C)
• 16 port Ethernet Switch (N-tron 516TX)
• 50 Watt 5V DC Power Supply (Omron or Astrodyne)
• DHCP Server (Asus RT-N56U)

There is nothing special about the hardware. As you can see, I used a wide variety of Beaglebone versions from two suppliers. The support structure is made of 20 mm extruded aluminum and an acrylic sheet:

Software Installation

Use the default operating system image or download a Debian console eMMC flasher such as BBB-eMMC-flasher-debian-7.7-console-armhf-2014-10-29-2gb.img.xz found at the elinux.org site.

Add the required tools:

>sudo apt-get install distcc distcc-pump g++ make

Compile Hosts Configuration

Choose one Beaglebone to set aside as the main build client. Ideally this would be the Beaglebone with the most memory (RAM and filesystem). The other seven "workers" will be referred to as compile hosts. In order to simplify the calling of distcc on the main build client, we need to give our workers hostnames. Run the following three commands on each of them:

> sudo nano /etc/hostname

> sudo nano /etc/hosts

> sudo hostname boris

In the 'hostname' and 'hosts' files, replace the default hostname (usually "beaglebone") with the desired hostname, which in the example above would be "boris".

A reboot will force an update to the hostname, but before we do that, we need to tell distcc to start a service at boot and to allow local network traffic. Edit the first few lines of the /etc/default/distcc config file:

> sudo nano /etc/default/distcc

to look something like this:

# Defaults for distcc initscript
# sourced by /etc/init.d/distcc

#
# should distcc be started on boot?
#
# STARTDISTCC="true"

STARTDISTCC="true"

#
# Which networks/hosts should be allowed to connect to the daemon?
# You can list multiple hosts/networks separated by spaces.
# Networks have to be in CIDR notation, f.e. 192.168.1.0/24
# Hosts are represented by a single IP Adress
#
# ALLOWEDNETS="127.0.0.1"

ALLOWEDNETS="192.168.0.0/24"

Reboot to commit the changes.

Main Build Client Configuration

Like we set up on the workers, we need to give the master a hostname. Two of the commands are identical:

> sudo nano /etc/hostname

> sudo hostname pluto

but we need to add the workers, in addition to the master hostname, to the hosts file:

> sudo nano /etc/hosts

Which, if your master unit is named "pluto", will look something like this:

127.0.0.1       localhost
127.0.1.1       pluto
192.168.0.106    droopy
192.168.0.71     astro
192.168.0.232    dogbert
192.168.0.9      scooby
192.168.0.100    underdog
192.168.0.139    snoopy
192.168.0.180    goofy
192.168.0.41     peabody
192.168.0.20     brian

That's it! We are now ready to run distcc.

Run distcc

Before we run distcc, we need to setup a couple of environment variables.

The first variable is handy if you are having trouble talking to workers, or would like more feedback from distcc:

> export DISTCC_VERBOSE=1

I found the extra output helpful in diagnosing issues.

The following command is necessary any time the list of client names changes. The order is important, but really only matters if you include the master in the worker list. Due to the limited resources on the Beaglebone, I chose not to allow normal building on the master.

> export DISTCC_POTENTIAL_HOSTS='astro dogbert snoopy underdog droopy scooby goofy peabody brian'

We can now call distcc, but instead of calling it directly, we are going to use the distcc-pump tool. Distcc-pump parses the "DISTCC_POTENTIAL_HOSTS" variable and automatically configures and starts the appropriate distcc services.

Most of the websites that show examples for distcc show something like this:

distcc-pump make -j12 CC="distcc"

which works, but when compiling large projects that are written in both C and C++, like Qt, that command only compiles SOME of the code on the cluster. Needless to say, this is bad and the master Beaglebone dies a quick death due to memory loss.

The workaround took me a while to figure out, but is really simple. Because distcc is smart enough to figure out which compiler to use, call this line instead:

> distcc-pump make -j12 CC=distcc CXX=distcc

Now that you have a working compiler, you can play around with the -j12 parameter to get the best results. Many distcc examples claim that this parameter could be very large, but that does not work for compiling a large project like Qt. The main choke point is the amount of RAM and the huge memory requirements for the include server.

Building Qt and Optimizations

Like I alluded to earlier, I did manage to compile Qt on the cluster, but it wasn't "clean". After a half hour of compiling, the master Beaglebone runs out of memory. It's not that big of a deal, because you can just run the distcc-pump command again, but I wanted to see if I could help it out.

To do this, I created 1 Gb of swap space on a micro SD card. This helped, but only extended the build time to an hour before the memory was full and the Beaglebone started spending most of it's time paging memory.

The ultimate solution was to use a master with more memory. I chose a Wandboard i.MX6 paired with a SATA HD, which worked well.

Here are the resultant compile times for various configurations:

Single Beaglebone                        ~19-20 hours
Beaglebone Master + 7 Beaglebone Workers ~5-6 hours
Beaglebone Master + 9 Beaglebone Workers ~5 hours
Wandboard Master + 8 Beaglebones         <4 hours

References

• http://www.manpagez.com/man/1/distcc/
• http://radekp.github.io/qtmoko/api/buildsystem/over-configure-options-qt-1.html

Qt 5.3.2 Beaglebone Binaries

Overview

If you saw my Qt 5.2 Binaries post, this will look very familiar....

Prerequisites

For this build, I wanted to try to enable support for everything. I got close, but didn't want to put forth the extra effort for the packages that were not obvious to install. You can mix and match the following installs, depending on your needs.

> sudo apt-get install libicu-dev

> sudo apt-get install libcups2-dev

> sudo apt-get install libudev-dev

> sudo apt-get install libmtdev-dev

> sudo apt-get install libegl1-mesa-dev

> sudo apt-get install libopenvg1-mesa-dev

KMS seems to be already installed (libdrm-dev), but the configuration script cannot find it. Also, some more research is needed before GLX can be enabled. The Debian package search tool is an awesome resource for finding files in packages.

Configuration

Here is the command line I used to generate the make files:

> ./configure -v -opensource -confirm-license -prefix /usr/local/qt-5.3.2 -qt-xcb

The cross compile feature changed slightly from 5.2, but 5.3 detects the local environment fairly well, so you no longer need to pass "-device" into the configuration script.

The Qt configuration script takes about 20 minutes to run on a rev. C Beaglebone Black. It first builds a native version of qmake, which takes about 15 minutes, then it tests for available modules.

Here is the configuration summary:

   Configure summary



Build type:    linux-g++ (arm, CPU features:)

Platform notes:



            - Also available for Linux: linux-kcc linux-icc linux-cxx



qmake vars .......... styles += mac fusion windows QT_LIBS_DBUS = -ldbus-1   QT_CFLAGS_DBUS = -I/usr/include/dbus-1.0 -I/usr/lib/arm-linux-gnueabihf/dbus-1.0/include   QT_HOST_CFLAGS_DBUS = -I/usr/include/dbus-1.0 -I/usr/lib/arm-linux-gnueabihf/dbus-1.0/include   QT_CFLAGS_GLIB = -pthread -I/usr/include/glib-2.0 -I/usr/lib/arm-linux-gnueabihf/glib-2.0/include   QT_LIBS_GLIB = -pthread -lgthread-2.0 -lrt -lglib-2.0   QT_CFLAGS_QGTKSTYLE = -pthread -I/usr/include/gtk-2.0 -I/usr/lib/arm-linux-gnueabihf/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/arm-linux-gnueabihf/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12   QT_LIBS_QGTKSTYLE = -lgobject-2.0 -lglib-2.0   QT_CFLAGS_QGTK2 = -pthread -I/usr/include/gtk-2.0 -I/usr/lib/arm-linux-gnueabihf/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/arm-linux-gnueabihf/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12   QT_LIBS_QGTK2 = -lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lgio-2.0 -lpangoft2-1.0 -lpangocairo-1.0 -lgdk_pixbuf-2.0 -lcairo -lpango-1.0 -lfreetype -lfontconfig -lgobject-2.0 -lglib-2.0   QT_CFLAGS_PULSEAUDIO = -D_REENTRANT -I/usr/include/glib-2.0 -I/usr/lib/arm-linux-gnueabihf/glib-2.0/include   QT_LIBS_PULSEAUDIO = -lpulse-mainloop-glib -lpulse -lglib-2.0   QMAKE_CFLAGS_FONTCONFIG = -I/usr/include/freetype2   QMAKE_LIBS_FONTCONFIG = -lfontconfig -lfreetype   QMAKE_INCDIR_LIBUDEV =   QMAKE_LIBS_LIBUDEV = -ludev   QMAKE_X11_PREFIX = /usr QMAKE_XKB_CONFIG_ROOT = /usr/share/X11/xkb QMAKE_INCDIR_EGL = /usr/include/libdrm   QMAKE_LIBS_EGL = -lEGL   QMAKE_CFLAGS_EGL =   QMAKE_CFLAGS_XCB =   QMAKE_LIBS_XCB = -lxcb   QMAKE_CFLAGS_DIRECTFB = -D_REENTRANT -I/usr/include/directfb   QMAKE_LIBS_DIRECTFB = -ldirectfb -lfusion -ldirect -lpthread   sql-drivers =  sql-plugins =  sqlite 
qmake switches .........



Build options:

  Configuration .......... accessibility accessibility-atspi-bridge alsa audio-backend c++11 clock-gettime clock-monotonic compile_examples concurrent cups dbus directfb egl egl_x11 eglfs evdev eventfd fontconfig full-config getaddrinfo getifaddrs glib gtk2 gtkstyle iconv icu inotify ipv6ifname large-config largefile libudev linuxfb medium-config minimal-config mremap mtdev nis no-harfbuzz opengl openssl openvg pcre png posix_fallocate precompile_header pulseaudio qpa qpa reduce_exports release rpath shared small-config system-freetype system-jpeg system-png system-zlib xcb xcb-plugin xcb-qt xcb-sm xcb-xlib xinput2 xkbcommon-qt xlib xrender

  Build parts ............ libs tools examples

  Mode ................... release

  Using C++11 ............ yes

  Using PCH .............. yes

  Target compiler supports:

    iWMMXt/Neon .......... no/auto



Qt modules and options:

  Qt D-Bus ............... yes (loading dbus-1 at runtime)

  Qt Concurrent .......... yes

  Qt GUI ................. yes

  Qt Widgets ............. yes

  Large File ............. yes

  QML debugging .......... yes

  Use system proxies ..... no



Support enabled for:

  Accessibility .......... yes

  ALSA ................... yes

  CUPS ................... yes

  Evdev .................. yes

  FontConfig ............. yes

  FreeType ............... yes (system library)

  Glib ................... yes

  GTK theme .............. yes

  HarfBuzz ............... no

  Iconv .................. yes

  ICU .................... yes

  Image formats:

    GIF .................. yes (plugin, using bundled copy)

    JPEG ................. yes (plugin, using system library)

    PNG .................. yes (in QtGui, using system library)

  journald ............... no

  mtdev .................. yes (system library)

  Networking:

    getaddrinfo .......... yes

    getifaddrs ........... yes

    IPv6 ifname .......... yes

    OpenSSL .............. yes (loading libraries at run-time)

  NIS .................... yes

  OpenGL / OpenVG:

    EGL .................. yes

    OpenGL ............... desktop

    OpenVG ............... yes-auto

  PCRE ................... yes (bundled copy)

  pkg-config ............. yes

  PulseAudio ............. yes

  QPA backends:

    DirectFB ............. yes

    EGLFS ................ yes

    KMS .................. no

    LinuxFB .............. yes

    XCB .................. yes (bundled copy)

      EGL on X ........... yes

      GLX ................ no

      MIT-SHM ............ yes

      Xcb-Xlib ........... yes

      Xcursor ............ yes (loaded at runtime)

      Xfixes ............. yes (loaded at runtime)

      Xi ................. no

      Xi2 ................ yes

      Xinerama ........... yes (loaded at runtime)

      Xrandr ............. yes (loaded at runtime)

      Xrender ............ yes

      XKB ................ yes

      XShape ............. yes

      XSync .............. yes

      XVideo ............. yes

  Session management ..... yes

  SQL drivers:

    DB2 .................. no

    InterBase ............ no

    MySQL ................ no

    OCI .................. no

    ODBC ................. no

    PostgreSQL ........... no

    SQLite 2 ............. no

    SQLite ............... yes (plugin, using bundled copy)

    TDS .................. no

  udev ................... yes

  xkbcommon .............. yes (bundled copy, XKB config root: /usr/share/X11/xkb)

  zlib ................... yes (system library)



NOTE: libxkbcommon and libxkbcommon-x11 0.4.1 or higher not found on the system, will use
the bundled version from 3rd party directory.

NOTE: Qt is using double for qreal on this system. This is binary incompatible against Qt 5.1.
Configure with '-qreal float' to create a build that is binary compatible with 5.1.

Info: creating super cache file /media/sda2/qt5.3.2/bbb_all/.qmake.super



Qt is now configured for building. Just run 'make'.

Once everything is built, you must run 'make install'.

Qt will be installed into /usr/local/qt-5.3.2



Prior to reconfiguration, make sure you remove any leftovers from

the previous build.

Before calling make, ensure that you have enough free space. The qt source folder starts at 920 Mb and will grow to 1.9 Gb during the compile (building only the libs requires 1.5 Gb and building libs and tools only requires 1.7 Gb). An additional 180 Mb is needed if a 'make install' is performed. I did a shadow build on a USB Flash drive (run /path/to/configure from an empty folder), as I was cutting it close on the internal eMMC. It took the BBB 12 hours to compile the libs only, 16 hours to compile the libs and tools, and 21 hours to compile libs, tools, and examples.

For convenience, I've included three zipped archives of the binaries for this build. The unlabeled build contains libs, tools, and examples. The others should be self explanatory. Once expanded, the libs package uses 94 Mb, the libs and tools package uses 104 Mb, and the full package uses 180 Mb

MD5SUM:
6dc968164bc532bea18b550f46660c3d  qt-5.3.2-no-examples.tar.xz(22 Mb)
ae7f9b7c8d0134e7c253500a64a9b9d7  qt-5.3.2-libs.tar.xz (18 Mb)
a735f85d028e1627fbfd031c58434ea5  qt-5.3.2.tar.xz (40 Mb)

Extract to /usr/local ('tar -xf file.tar.xz'), as the tarball contains the qt-5.3.2 folder in it.

Beaglebone Debian Read Only Filesystem

Overview

To save the eMMC and to allow for faster bootup/shutdowns, I wanted to mount the root partition as read-only. I spent many days researching and trying to find out what areas of the filesystem needed to have write permissions. It seemed like I was going in circles. Unionfs, aufs, mount -bind, overlayfs, tmpfs.....so many options and so many modules that didn't exist in the default BBB Debian kernel. I finally got so fed up that I decided to just start hacking away at the fstab.

Details

It turns out that the basic read-only filesystem is fairly easy to create, as everything that needs to be configured is contained in /etc/fstab. We need to change the root mount to read-only and add a couple of temporary file systems to handle logs and such. Let's start with an ordinary fstab created by the eMMC flasher script:

# /etc/fstab: static file system information.

#

# Auto generated by: beaglebone-black-eMMC-flasher.sh

#

UUID=716e1ca7-bc61-4958-8c0d-665e48102cfd  /  ext4  ro,noatime,errors=remount-ro  0  1

UUID=0DFE-E81B  /boot/uboot  auto  defaults  0  0

debugfs         /sys/kernel/debug  debugfs  defaults          0  0

We could then use the following sed command to add the "ro" tag to the root mount line and save it to a temporary fstab file:

> sudo sed s:ext4\ \ noatime:ext4\ \ ro,noatime: /etc/fstab_ro

Next we need to append some tmpfs declarations to our temporary fstab file:

> sudo nano /etc/fstab_ro

and put the following lines at the end:

tmpfs           /tmp  tmpfs  nodev,nosuid,size=32M  0  0

tmpfs           /srv  tmpfs  nodev,size=512K  0  0

tmpfs           /var/log  tmpfs  defaults,noatime,size=1M  0  0

tmpfs           /var/tmp  tmpfs  defaults,noatime,size=512K  0  0

tmpfs           /var/run  tmpfs  defaults,noatime,size=512K  0  0

Replace the real /etc/fstab with your temporary file:

> sudo cp /etc/fstab /etc/fstab.orig

> sudo mv /etc/fstab_ro /etc/fstab

Reboot and you're done!

You may have to experiment with different size limits, depending on your logging needs, but the sizes above should get you started.

Alternate Method

Systemd does the actually mounting, by parsing the fstab. The order in which the mounts are created is not guaranteed. If you need to create mounts in a particular order you need to create a systemd .mount unit for each mount:

> sudo nano /etc/systemd/system/my.mount

with content similar to the following:

[Unit]

Description=Runtime Directory

Before=local-fs.target



[Mount]

What=/mine

Where=/tmp/myfs

Type=bind

Options=bind

Remount RW

If you need to modify the filesystem, you can remount it rw, for a while, with the following command:

> sudo mount -o remount,rw /

To return to read-only mode, either reboot or run this command:

> sudo mount -o remount,ro /

References

https://groups.google.com/forum/#!topic/beagleboard/9J2r8xn3-Os
http://adis.ca/tag/beaglebone/
http://unix.stackexchange.com/questions/27449/mount-a-filesystem-read-only-and-redirect-writes-to-ram
https://help.ubuntu.com/community/aufsRootFileSystemOnUsbFlash
http://unix.stackexchange.com/questions/81959/how-to-mount-aufs-file-system-on-boot-in-archlinux
http://www.thegeekstuff.com/2013/05/linux-aufs/
https://wiki.debian.org/ReadonlyRoot
https://code.google.com/p/rootaufs/wiki/HowToUse

TFTP and NFS Debian on Beaglebone Black

Overview

Back when I was working with kernel 3.2 and the TI Linux SDK, I had the Beaglebone booting to a NFS. I thought it would be nice to do that again, because it is very convenient for development purposes.

Downloads

Get this if you don't already have a micro SD card with an image on it:
Debian eMMC Flasher (can also be used as a live system): Official Image, Other Versions

Background

I will break up the configuration into three parts:

• TFTP
• NFS
• Local bootstrap

Qt 5.2.1 Beaglebone Binaries

Overview

So, how did I create these binaries....well I thought it would be fun to see how long it would take the Beaglebone to compile Qt. Here is a brief description of my setup.

I powered the Beaglebone with a 5v power supply and booted a Debian rootfs using TFTP and NFS (a future post will explain how to configure this) so I could utilize the large HD of my Linux host. After compiling and installing Qt, the total root filesystem usage is around 3 Gb. The actual compile took about 21 hours, which includes compiling all examples and plugins.

Configuration

I created a simple shell script to modify the Qt source, with the Beaglebone configuration, and run the Qt configuration script:

#!/bin/sh




# Create beaglebone hard float configuration file

cd qt-everywhere-opensource-src-5.2.1/qtbase/mkspecs/devices/

cp -r linux-beagleboard-g++ linux-beaglebone-g++

sed 's/softfp/hard/' <linux-beagleboard-g++/qmake.conf >linux-beaglebone-g++/qmake.conf





# Run configuration


cd ../../../

./configure -v -opensource -confirm-license -prefix /usr/local/qt-5.2 -no-largefile -no-accessibility -qt-zlib -no-gif -qt-libpng -qt-libjpeg -no-nis -no-cups -device linux-beaglebone-g++

This produced the following summary:

   Configure summary




Build type:    linux-g++ (arm, CPU features:)

Platform notes:




            - Also available for Linux: linux-kcc linux-icc linux-cxx

        

qmake vars .......... styles += mac fusion windows DEFINES += QT_NO_MTDEV QT_CFLAGS_DBUS = -I/usr/include/dbus-1.0 -I/usr/lib/arm-linux-gnueabihf/dbus-1.0/include   QT_LIBS_DBUS = -ldbus-1   QT_CFLAGS_GLIB = -pthread -I/usr/include/glib-2.0 -I/usr/lib/arm-linux-gnueabihf/glib-2.0/include   QT_LIBS_GLIB = -pthread -lgthread-2.0 -lrt -lglib-2.0   QT_CFLAGS_PULSEAUDIO = -D_REENTRANT -I/usr/include/glib-2.0 -I/usr/lib/arm-linux-gnueabihf/glib-2.0/include   QT_LIBS_PULSEAUDIO = -lpulse-mainloop-glib -lpulse -lglib-2.0   DEFINES += QT_NO_LIBUDEV QMAKE_CFLAGS_XCB =   QMAKE_LIBS_XCB = -lxcb   QMAKE_CFLAGS_DIRECTFB = -D_REENTRANT -I/usr/include/directfb   QMAKE_LIBS_DIRECTFB = -ldirectfb -lfusion -ldirect -lpthread   sql-drivers =  sql-plugins =  sqlite qmake switches ......... 




Build options:

  Configuration .......... alsa audio-backend c++11 clock-gettime clock-monotonic compile_examples concurrent dbus directfb evdev eventfd full-config getaddrinfo getifaddrs glib iconv inotify ipv6ifname large-config linuxfb medium-config minimal-config mremap neon no-gif no-harfbuzz opengl openssl pcre png posix_fallocate precompile_header pulseaudio qpa qpa reduce_exports reduce_relocations release rpath shared small-config system-freetype xcb xcb-qt xkbcommon-qt xlib zlib 

  Build parts ............ libs tools examples

  Mode ................... release

  Using C++11 ............ yes

  Using PCH .............. yes

  Target compiler supports:

    iWMMXt/Neon .......... no/yes




Qt modules and options:

  Qt D-Bus ............... yes (loading dbus-1 at runtime)

  Qt Concurrent .......... yes

  Qt GUI ................. yes

  Qt Widgets ............. yes

  JavaScriptCore JIT ..... yes (To be decided by JavaScriptCore)

  QML debugging .......... yes

  Use system proxies ..... no




Support enabled for:

  Accessibility .......... no

  ALSA ................... yes

  CUPS ................... no

  FontConfig ............. no

  FreeType ............... system

  Iconv .................. yes

  ICU .................... no

  Image formats: 

    GIF .................. no

    JPEG ................. yes (plugin, using bundled copy)

    PNG .................. yes (in QtGui, using bundled copy)

  Glib ................... yes

  GTK theme .............. no

  Large File ............. no

  mtdev .................. no

  Networking: 

    getaddrinfo .......... yes

    getifaddrs ........... yes

    IPv6 ifname .......... yes

    OpenSSL .............. yes (loading libraries at run-time)

  NIS .................... no

  OpenGL ................. desktop

  OpenVG ................. no

  PCRE ................... yes (bundled copy)

  pkg-config ............. yes 

  PulseAudio ............. yes

  QPA backends: 

    DirectFB ............. yes

    EGLFS ................ no

    KMS .................. no

    LinuxFB .............. yes

    XCB .................. yes (bundled copy)

      MIT-SHM ............ yes

      Xcb-Xlib ........... no

      Xcursor ............ yes (loaded at runtime)

      Xfixes ............. yes (loaded at runtime)

      Xi ................. yes (loaded at runtime)

      Xi2 ................ no

      Xinerama ........... yes (loaded at runtime)

      Xrandr ............. yes (loaded at runtime)

      Xrender ............ no

      XKB ................ yes

      XShape ............. yes

      XSync .............. yes

      XVideo ............. yes

  Session management ..... yes

  SQL drivers: 

    DB2 .................. no

    InterBase ............ no

    MySQL ................ no

    OCI .................. no

    ODBC ................. no

    PostgreSQL ........... no

    SQLite 2 ............. no

    SQLite ............... yes (plugin, using bundled copy)

    TDS .................. no

  udev ................... no

  xkbcommon .............. yes (bundled copy)

  zlib ................... yes (bundled copy)




NOTE: libxkbcommon 0.2.0 (or higher) not found on the system, will use 

the bundled version from 3rd party directory.

NOTE: Qt is using double for qreal on this system. This is binary incompatible against Qt 5.1.

Configure with '-qreal float' to create a build that is binary compatible with 5.1.

If you've tried cross compiling Qt, from my other posts, you will notice a lot more modules are enabled in this build.

I've tested a few examples and they all work, but I have not tested everything (haven't been able to test touch screen stuff yet). The examples default to using X11, if you want to use the linuxfb, add '-platform linuxfb' to the command line options. For example:

> analogclock -platform linuxfb

Here are two versions of binaries, one that includes examples (78 Mb) and one that does not (36 Mb).

MD5SUM:
9395fc70f576e58b68df7d732a002abb  qt-5.2-no-examples.tgz
f698f038166c4b2f65cec40056e23db2  qt-5.2.tgz

Extract to /usr/local, as the tarball contains the qt-5.2 folder in it.

If you want to try your hand at compiling applications on the Beaglebone, these packages have a native qmake included. Don't forget to add /usr/local/qt-5.2/bin to your path.

Have fun!

Why Qt Development was stalled....

I finally finished my digital I/O cape! It only took about two and a half hours to hand solder all of the components. It is fully tested and ready to go.

It has an isolated DC to DC converter, 16 optically isolated digital inputs and 16 optically isolated digital outputs, a 4 wire RS-422 port, and an optically isolated 2 wire RS-485 port.

I have released the Eagle 6.5 project files, for my older v1.0 board (v2.0 is in the photo), on GitHub: https://github.com/compeoree/bb-dio-cape.

Now back to Qt 5.....

element14 BB-View and the Debian Beta

This is a post I made at the element14 Community pages:

I thought some other might like to know how to get the BB-View working under the latest Debian beta images.

Unfortunately, you are going to have to recompile the Kernel. The video works fine without a recompile (the red/blue swap is easy to fix), but the touchscreen control connections are not the same as the standard TI 4-wire interface. I tried to patch the ti_am335x_tsc.c file, so the changes would be limited to a dts recompile, but I haven't been able to get that working yet (I'm pretty sure it is a state machine / bit assignment issue). But anyway, here are the steps that you need to perform.....

Overview

1) Download the necessary files

     a) Robert Nelson's handy tools for compiling the Beaglebone kernel

     b) BB-View source for Angstrom

2) Build the default kernel

3) Patch the Kernel and perform a fast recompile

4) Copy the new kernel to the Beaglebone

5) Edit the xorg.conf file to correct the Red/Blue color swap

6) Revel in the 4 days you just saved 

Let's Get Started

I am using Ubuntu 12.04 LTS 64 bit running in a VirtualBox VM to compile the kernel:

Make a new folder called bb-view, this is where our build will happen.

> mkdir bb-view

> cd bb-view

Install git, if you haven't already:

> apt-get install git

Clone Robert Nelson's linux-dev project locally. Be prepared for a large download (~100 Mb for the cross-compiler and ~700 Mb for the kernel source).

> git clone https://github.com/RobertCNelson/linux-dev.git

Change into the new linux-dev folder and select branch/tag that matches the Debian version.

> cd linux-dev

> git checkout 3.8.13-bone37 -b tmp

Now we need to build the base image, so our cape drivers folder gets populated. The script will tell you if you need to do or install anything else. 

> ./build_kernel.sh

Come back in an hour or so.....(You might want to download the Angstrom source from element14 now)

Patching the Kernel

Extract two files from the Angstrom source:

> unzip angstrom-source.zip

> tar -zxf bb-black-kernel-3.8.13-bb-view.tar.bz2

> cp ./kernel/kernel/drivers/input/touchscreen/ti_am335x_tsc.c  ~/bb-view/linux-dev/KERNEL/drivers/input/touchscreen/

> cp ./kernel/kernel/firmware/capes/BB-VIEW-LCD7-01-00A0.dts  ~/bb-view/linux-dev/KERNEL/firmware/capes/

Now we need to let the compiler know that we want to add the firmware to the build:

> nano   ~/bb-view/linux-dev/KERNEL/firmware/Makefile

Add the following line somewhere near line 192 (CTRL-C will display current cursor position):

BB-VIEW-LCD7-01-00A0.dtbo \

Don't forget the trailing backslash....it is important. Now save and exit by doing CTRL-O, Enter, CTRL-X.

Change back to the linux-dev root folder:

> cd   ~/bb-view/linux-dev

Now issue the kernel rebuild command, this won't take very long at all:

> ./tools/rebuild.sh

Copy Kernel to BBB

The following instructions assume that you already have the Debian beta installed and booted up on the BBB.

The easiest way is to copy the files over the network, via the 'scp' command:

> scp   ~/bb-view/linux-dev/deploy/3.8.13-bone37.zImage   debian@192.168.7.2:/home/debian

Replace debian (both instances) with the username you are running on the BBB and 192.168.7.2 with the IP address of the BBB.

Now log into the BBB and copy the kernel image to the boot partition:

> ssh debian@192.168.7.2

bbb>  sudo cp 3.8.13-bone37.zImage   /boot/uboot/zImage

We need to do one more thing before the LCD will work. Since the cape doesn't have an EEPROM, we need to black-list the HDMI drivers and force-load the BB-VIEW drivers in the boot command file:

bbb>  sudo  nano  /boot/uboot/uEnv.txt

Find the "optargs" line and edit it to be:

optargs=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN  capemgr.enable_partno=BB-VIEW-LCD7-01

Notice that the preceding "#" has been removed. You don't want to disable BB-BONE-EMMC-2G, or you won't be able to boot from eMMC.

Now save and exit by doing CTRL-O, Enter, CTRL-X.

Reboot the BBB and the LCD should now work....except the blue and red are reversed.

Fixing Red/Blue Color Swap

This is due to errata in the TI AM335x processor when switching between 16 and 24 bit video modes. To fix this, we must first find the name of our screen:

> ssh debian@192.168.7.2

bbb> cat  /var/log/Xorg.0.log  |  grep  screen

Mine was "Builtin Default fbdev Screen 0"

Now we edit our X configuration file:

bbb> sudo nano  /usr/share/X11/xorg.conf.d/10-evdev.conf

and add a "Screen" section at the end of the file:

Section "Screen"

        Identifier "Builtin Default fbdev Screen 0"

        Monitor "Configured Monitor"

        Device "Configured Video Device"

        DefaultDepth 24

EndSection

Save and exit by doing CTRL-O, Enter, CTRL-X.

Reboot and enjoy!

Bare Metal Qt 5.2 on BeagleBone Black Ubuntu - Part 3

Overview

With Qt 5.2 working on the BeagleBone Black, created in Part 1 and Part 2, now it is time to compile a "Hello World" application. Assumptions:

• You are using an Ubuntu x64 host for creating Qt applications
• You have a Linaro toolchain located under /usr/local/linaro
• You have a BeagleBone connect to your host PC via a LAN

Downloads

No need to compile our own Qt Creator, just download it:

• Qt Creator 3.0.0 Installer: Direct Link, Others

Video Tutorials

Derek Molloy has three excellent videos about Qt on the BeagleBone. I suggest you start with these, as it will make following these instructions easier.

• Part 1: BeagleBone LCDs and Qt
• Part 2: Using Qt Creator
• Part 3: A fully featured application

Setup Toolchain Environment

Open Qt Creator

Go to Tools -> Options

Add a new Device

Click on "Devices" from the list on the left

Click the "Add..." button on the upper right

Select Generic Linux Device

Click "Start Wizard" button

Enter "BBB - Ubuntu" for the name

Enter IP, and user information.

Click "Next" button

Click "Finish" button

Verify that the test connection was successful

Add a new Compiler

Click on the "Build & Run" item from the list on the left

Click on the "Compilers" tab

Click the "Add" drop down list button and select GCC

Change the name to "Linaro GCC"

Click the "Browse..." button next to the "Compiler path" field

Enter "/usr/local/linaro/bin/" into the filename field and click "Open"

Select "arm-linux-gnueabihf-g++" and click "Open" again

Click the "Apply" button

Add a new Debugger

Click on the "Debuggers" tab

Click the "Add" button

Enter "Linaro GDB" for the name

Click the "Browse..." button next to the Path field

Select "arm-linux-gnueabihf-gdb" and click "Open"

Click the "Apply" button

Add a new Qt Version

Click on the "Qt Versions" tab

Click the "Add..." button

Navigate to "/usr/local/qt-5.2/bin/qmake"

Click the "Open" button

Click the "Apply" button

Add a new Kit

Click on the "Kits" tab

Click the "Add" button

Change name to "BBB Kit"

Ensure that the device type is "Generic Linux Device"

Ensure that the device is "BBB - Ubuntu"

Select the "Linaro GCC" compiler from the Compiler drop down list button

Select the "Linaro GDB" debugger from the Debugger drop down list button

Select the "Qt 5.2.0 (qt-5.2)" version from the "Qt Version" drop down list button

Click the "Ok" button

Create a New Console Project

Under the Welcome page, Click the "New Project" button

Select "Applications" from the list on the left

Select "Qt Console Application"

Click the "Next" button

Enter "HelloWorld" in the name field

Change the target directory, if you like

Click on the "Next" button

Review the details and then click on the "Next" button

Click on the "Finish" button

Modify Auto-Generated Project

Edit main.cpp to look like this:

#include <QCoreApplication>
#include <iostream>
using namespace std;

int main(int argc, char *argv[])
{

   QCoreApplication a(argc, argv);

   cout << "Hello World!" << endl;

   return a.exec();

}

This will build locally, but we want it to auto deploy to the BeagleBone. That's coming up next...

Create Deploy Configuration

Add the following three lines to HelloWorld.pro after the "TARGET=HelloWorld" line

   target.files = HelloWorld
   target.path = /home/ubuntu
INSTALLS += target

That's it, now Qt Creator will automatically deploy the files before a debug or run.

Install GDB Server

This is required in order to debug from Qt Creator running on our host PC. This only needs to be done once. Issue this command on the Beaglebone:

> sudo apt-get install gdbserver

Now you can press the Debug icon (looks like a play arrow) in Qt Creator and it will automatically scp the binary to the BeagleBone and start a remote GDB server session.

Create a GUI Project

Under the Welcome page, Click the "New Project" button

Select "Applications" from the list on the left

Select "Qt Gui Application"

Note: This option may not show up. If Qt Creator does not see the Qt 5.2 build as supporting GUI applications,  you can choose "Qt Widgets Application", but this may give different results. The other option is to install a distro version of Qt and make Qt Creator aware of it. This will make the Gui option visible in the project creation section. Nevermind, this is a difference between Qt Creator 2.8 and 3.0. The source generated, for either option, is identical.

Click the "Next" button

Enter "HelloWorldGUI" in the name field

Change the target directory, if you like

Click on the "Next" button

Review the details and then click on the "Next" button

Click on the "Finish" button

Modify Auto-Generated Project

Perform the same .pro file changes, as the console project, to deploy the project to the Beaglebone.