Dedicated SBC Camera Monitor
A guide to setup an SBC (beaglebone black) or Desktop that will monitor a video feed from ZM. Simply press the power button, and the video feed will appear on boot.
OS will be Devuan Jessie, WM will be dwm, terminal st, and browser will be surf. It will be a minimal installation. Leaner than LXDE, the default DE for beaglebone.
I'll include optional steps to setup the I2C peripheral (BBB) and read a sensor. Combine with ZMTrigger.
This is noticeably more difficult than connecting a coaxial cable to a CRT such that an analog, older setup would have.
Setup
Installation
Requirements
- At least 4GB SD
- SBC / Desktop / Laptop
- Internet connection
- Computer monitor
- HDMI cable for BBB (I use a HDMI to DVI adaptor)
- Novice to Intermediate GNU/Linux experience
Install Beaglebone Black Debian Jessie using elinux.com's BeagleBoardDebian page.
Use the direct image (under Demo, below NetInstall). Not the netinstall, which is slower, unless you know what you are doing.
After booting from the SD card, make sure the network interface is set to load in:
nano /etc/network/interfaces
Next, migrate to Devuan using Dev1fanboy Upgrade-Install-Devuan wiki guide. Skip most of the part about the display environment. Reboot after apt-get dist-upgrade. Try the purge of libsystemd0 in DE section, if you like. May not work. RCN repo seems to want it.
Complete the following commands
sudo su
apt-get install xorg libx11-dev libxft-dev libxinerama-dev gcc make htop sudo tcpdump
For Surf
apt-get install libwebkitgtk-dev libgtk2.0-dev linux-headers-$(uname -r)
Download simple programs
git clone http://git.suckless.org/dwm && git clone git://git.suckless.org/st && git clone git://git.suckless.org/surf
Edit the config for dwm
nano dwm/config.def.h
- Later Disable the bar
- Later Remove all workspaces except for 1 (*tags)
- Set Mod4Mask as modkey (redmond key)
- Set MODKEY|Shiftmask to 0 and XK_c to XK_F12 for killclient (personal preference)
- Later disable spawm of dmenucmd and termcmd, but for now leave enabled.
cd dwm make make install cd ../st nano config.def.h
- Set termname[] to xterm (resolves some issues with programs that don't understand default termname).
make make install cd ../surf nano config.def.h
- Review options
- Later set runinfullscreen to TRUE
- Later set kioskmode to TRUE once debugging is over
make make install
Cleanup
apt-get remove nfs-common rpcbind wpasupplicant avahi-daemon ofono apache2
Leave wpasupplicant if you use wifi. Net installer may want to install acpid. Beware of removing cron. Just disable the service. Remove Exim4 if you want.
At this point maybe 40MB RAM, and <5% CPU. Compare to LXDE.
Clock
Only needed if you are keeping time.
# apt-get install ntpdate
Set cron to run ntpdate periodically
*/5 * * * * ntpdate pool.ntp.org
This is leaner than running ntpd 24/7
Auto Start
Edit .xinitrc, /etc/rc.local, /etc/inittab, and .bash_profile to auto startx without requiring a login, load surf with the path of the zm server monitor feed, and disable the screensaver.
Added to /etc/inittab (replace existing):
1:2345:respawn:/bin/login -f USERNAME tty1 </dev/tty1 >/dev/tty1 2>&1
Copy /etc/profile to user that will be auto logging in:
cp /etc/profile ~/.bash_profile
Appended to ~/.bash_profile for USERNAME:
exec startx
When startx loads, it will pull settings from ~/.xinitrc for USERNAME so edit that (note that .xinitrc requires & after all commands that are not the final wm).
#!/bin/bash /usr/local/bin/surf "localhost/zm/cgi-bin/nph-zms??mode=jpeg&monitor=1&scale=100&maxfps=5&buffer=1000&user=user&pass=pass" & exec dwm
Add another user beside the one used for the auto login, otherwise ssh will fail. ssh will try to startx when it loads, and it won't be able to. Add USERNAME2 permissions to sudoers.
# adduser USERNAME2 nano /etc/sudoers
Disable screensaver per Arch Wiki: Display Power Management SIgnaling
nano ~/.xinitrc export DISPLAY=:0 & xset s off & xset -dpms &
These go before the other commands in .xinitrc, as they have the & symbol.
Note: When troubleshooting xset. You must be the same user that is running X (ssh in as different user, then su to user). And, you must export DISPLAY to :0 or similar. Finally xset q should query the current settings.
Fine Tuning
At this point, you should be able to boot the SBC or desktop and receive a video feed without user interaction. However there are two problems. One, it is not full screen. Two, video may be flickering.
Flickering Video
This is a known issue with Beaglebone. The simple solution is: install devmem2 or some other memory editing program, change an address. For details of why this is occuring see: [1] and [2] or search online.
Steps:
git clone https://github.com/VCTLabs/devmem2 cd devmem2 make make install
Append the memory adjustment to rc.local
nano /etc/rc.local devmem2 0x4c000054 w 0x00FFFFF10
Watch syslog and FIFO errors should immediately stop upon entering write command on memory.
Install steps source: Scivision: Devmem2 on the beaglebone black The author of devmem2 (Jan-Derk Bakker, website and code found at lartmaker.nl), his website is down at the moment. You can view the root domain at internet archive, but the page for devmem2 is not available. Others like VCTLabs above have copied his code to various spots.
Full Screen Video Feed
Two options come to mind:
- Point browser to a local html page with the link to the monitor embedded in an img tag
OR
- have a local web server run and point surf to a hosted html page.
First Is easiest. Make an html file. Be sure to include http prefix.
<html> <img width="###px" height=###px" src="http://serverip/zm/cgi-bin/nph-zms?mode=jpeg&monitor=####&scale=100&maxfps=5&user=username&pass=password" /> </html>
Call it on .xinitrc
surf file:///home/username/file.html
Customize the width and height of the img tag to fit your monitor. In my case I put st in the .xinitrc
of my bbb instead of surf, restarted, and from the terminal ran xrandr to see what display it was using. I had 1440x900 but the width and height I could get out of surf without borders causing trouble was 1415 and 875. Multiple img tags can be embedded into an html file however you like.
This procedure has been tested 03/2017 on Devuan Jessie and a Beagle.
Using the Breakout Headers
Device Trees and Pin Initialization
Here are some notes, from my own setup of I2C on the BBB. It can be confusing if you are new to the BBB. This guide is helpful for configuring the peripherals or GPIO of the BBB.
https://github.com/beagleboard/bb.org-overlays
Follow this link. Ignore the part about pre built kernels if you used the RCN based installer or image from elinux.org's BeagleBoardDebian. You already have cape manager support.
If you don't have DTC where is asks for it in the 2nd step for dtc -version, ignore that step. The ./dtc_overlay.sh script will install the latest compatible device tree compiler.
Next
https://github.com/cdsteinkuehler/beaglebone-universal-io
And use this to configure the pins.
There are also preset modes with the pins configured in various states, but I found it more satisfying to customize them to my needs.
cd .. git clone https://github.com/cdsteinkuehler/beaglebone-universal-io cd beaglebone-universal-io
No installation is required for config-pin.
Test it now:
./config-pin overlay cape-universal
This will allow a lot of pins to be edited. This must be done first. Then you can configure pins. There are other modes as well, see github. Cape-universal exports all pins except for HDMI and EMMC pins.
#:~/beaglebone-universal-io# cat /sys/devices/platform/bone_capemgr/slots 0: PF---- -1 1: PF---- -1 2: PF---- -1 3: PF---- -1 7: P-O-L- 0 Override Board Name, 00A0,Override Manuf, cape-universal
Now you can run something like this:
./config-pin p8_07 hi
To set Pin 07 on header 8 to GPIO HI
To see more options
./config-pin -h
e.g.
./config-pin -l 9_11 default gpio gpio_pu gpio_pd uart
Showing us we can set the pin to UART or one of the GPIO modes.
./config-pin -a 9_11 uart
Then we can access the UART through either the direct memory registers, or the linux file system access (search online for more details).
The config-pin overlay cape-universal can be set in /etc/rc.local as well as individual pin settings.
I2C Usage
# apt-get install i2c-tools
List
# i2cdetect -l
The i2c peripheral, after being connected to the BBB, will be on one of the three i2c buses. Either 0,1, or 2.
# i2cdetect -r 0
Here we search on 0.
I used a BMP180 barometer and mine showed up at 77.
Unfortunately, the sensor can't be read from without a driver. What you will need to do is recompile the kernel with that driver included, as linux has a driver for the BMP085, but not by default.
References: (from http://elinux.org/EBC_Exercise_12_I2C) [3] [4]
Recompile Kernel With Sensor Driver
I tried building the kernel natively on the Beagle, but this failed. It is best to cross compile from a Debian based distro. I received an error trying to cross compile on Gentoo.
http://elinux.org/EBC_Installing_Kernel_Source is a good guide that doesn't require javascript (as RCN's docs do).
Finally, with the kernel built with support for your i2c device, (in this case a barometer):
su root echo bmp085 0x77 > /sys/class/i2c-adaptor/i2c-1/new_device
Again, these steps are only valid for the bmp085, and when it's on i2c-1. Review dmesg
$ dmesg -T
Finally for the BMP085, you can navigate to /sys/bus/i2c/drivers/bmp085/1-0077/ and review what the file system provides access to from the BMP driver to interface with the sensor.
Troubleshooting
Video feed freezes once a day?
Installing and updating programs takes too long!
While these SBCs are slower than a desktop, it is also possible you have a counterfeit SD card that is slowing down all installs. A counterfeit or non name brand SD may take one day, what takes 2 hours to do with a name brand card.
Video feed flickers, syslog says FIFO underflow!
See install steps regarding adjusting memory addresses with devmem2.
How do I disable keypresses, or whatnot for a real kiosk mode?
Look online. I don't have the need, so I have omitted it, but it's possible to do further lockdown.
