Posts Tagged Dash-Cam

Prevent Motion From Running Without a Camera Connected

Posted by Gary A. Stafford in Bash Scripting, Raspberry Pi, Software Development on July 19, 2013

Introduction

If you read my post, Raspberry Pi-Powered Dashboard Video Camera Using Motion and FFmpeg, you know Motion with FFmpeg on a Raspberry Pi makes an ideal dashboard camera system. However, an issue I still struggled with when using the dash-cam was Motion running without a webcam connected.

When I start my car, the Raspberry Pi boots-up, and subsequently, Motion starts. No interaction with the Pi is required. The dash-cam starts capturing images and making the time-lapse video. However, when I get home and plug my Pi back into my local network, Motion starts up again and starts recording blank images and creating the time-lapse video, even though there is no webcam connected.

To get prevent Motion from starting up without a webcam connected, I’ve added a simple function to the Motion startup script. When the system calls Motion on startup,  the new function checks if a webcam is connected. If not, it immediately exits the script, without ever starting Motion. No blank images or empty time-lapse videos are created. This saves a lot of wasted processing on the Pi. It also saves a lot of wasted time moving videos and images off the Pi that end up being blank, because no webcam was connected.

Find Your Webcam

First, attach your webcam to the Raspberry Pi. Run the following command to list the USB devices connected to the Pi:

lsusb

You should see similar output to the example below. Note your webcam’s ID(s). I ran the command twice in this example, to identify both of my webcams.

Identifying Webcams with lsusb Command

Identifying Webcams with lsusb Command

There are several ways to detect your webcam, depending on you Linux distro. I found this post particularly helpful, The Webcam HOWTO.

Modify Motion

Next, open the Motion startup script, using the following command:

sudo nano /etc/init.d/motion

Add the following ‘check_for_webcam ()’ function to the top of the script, adjacent to the existing ‘check_daemon_enabled()’ function:

# Check if specific webcam(s) are connected to Pi
check_for_webcam () {
    if lsusb | grep -s -q -e 0000:ABCD
    then
        echo "Webcam found. Continuing..."
        return 0
    else
        echo "No webcam found? Shutting down Motion!"
        return 1
    fi
}

You will need to modify the function, changing the string ‘0000:ABCD’, to match your webcam’s ID. If you change your webcam model, remember to update the ID you entered in this function.

Next add the following statement to the beginning of the ‘start’ function.  This code calls the new function when Motion’s ‘start’ command is executed. If no webcam is found, the Motion script exits without starting.

if ! check_for_webcam; then
    exit 1
fi

In my example below, I have two possible webcams that might be connected, so I search (grep) for either ID.

Modifying Motion Startup Script

Modifying Motion Startup Script

Testing the Script Change

Save and close the Motion script. To test the script is working, run the following command to stop Motion:

sudo /etc/init.d/motion stop

Unplug your webcam from the Raspberry Pi. Then, run the following command to start Motion:

sudo /etc/init.d/motion start

You should see the following output:

No webcam found? Shutting down Motion!

Now, plug your webcam back in and run the ‘start’ command, again. You should now see the following output:

Webcam found. Continuing...
Starting Motion With and Without WebCam

Starting Motion With and Without Webcam

Conclusion

Now, when you start the Raspberry Pi and don’t have a web-cam connected, Motion will no longer automatically start. Just remember, if you don’t have a way to interact directly with your Pi, you will need to restart the Pi to get Motion running again after connecting a webcam.

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Travel-Size Wireless Router for Your Raspberry Pi

Posted by Gary A. Stafford in Bash Scripting, Raspberry Pi, Software Development on July 15, 2013

Use a low-cost nano-size wireless router to connect to your Raspberry Pi while traveling. Set up your own private wireless network in your vehicle, hotel, or coffee shop.

Introduction

Recently, I purchased a USB-powered wireless router for to use with my Raspberry Pi when travelling. In an earlier post, Raspberry Pi-Powered Dashboard Video Camera Using Motion and FFmpeg, I discussed the use of the Raspberry Pi, combined with a webcam, Motion, and FFmpeg, to create a low-cost dashboard video camera. Like many, I find one the big challenges with the Raspberry Pi, is how to connect and interact with it. Being in my car, and usually out of range of my home’s wireless network, except maybe in the garage, this becomes even more of an issue. That’s where adding an inexpensive travel-size router to my vehicle comes in handy.

I chose the TP-LINK TL-WR702N Wireless N150 Travel Router, sold by Amazon. The TP-LINK router, described as ‘nano size’, measures only 2.2 inches square by 0.7 inches wide. It has several modes of operation, including as a router, access point, client, bridge, or repeater. It operates at wireless speeds up to 150Mpbs and is compatible with IEEE 802.11b/g/n networks. It supports several common network security protocols, including WEP, WPA/WPA2, WPA-PSK/WPA2-PSK encryption. For $22 USD, what more could you ask for!

TP-LINK Nano Router

My goal with the router was to do the following:

  1. Have the Raspberry Pi auto-connect to the new TP-LINK router’s wireless network when in range, just like my home network.
  2. Since I might still be in range of my home network, have the Raspberry Pi try to connect to the TP-LINK first, before falling back to my home network.
  3. Ensure the network was relatively secure, since I would be exposed to many more potential threats when traveling.

My vehicle has two power outlets. I plug my Raspberry Pi into one outlet and the router into the other. You could daisy chain the router off the Pi. However, my Pi’s ports are in use my the USB wireless adapter and the USB webcam. Using the TP-LINK router, I can easily connect to the Raspberry Pi with my mobile phone or tablet, using an SSH client.

Using Fing to Locate the Pi on the TP-LINK Wireless Network

Using Fing to Locate the Pi on the TP-LINK Wireless Network

When I arrive at my destination, I log into the Pi and do a proper shutdown. This activates my shutdown script (see my last post), which moves the newly created Motion/FFmpeg time-lapse dash-cam videos to a secure folder on my Pi, before powering down.

Using SSH Terminal for iOS to Shutdown the Pi

Using SSH Terminal for iOS to Shutdown the Pi

Of course there are many other uses for the router. For example, I can remove the Pi and router from my car and plug it back in at the hotel while traveling, or power the router from my laptop while at work or the coffee shop. I now have my own private wireless network wherever I am to use the Raspberry Pi, or work with other users. Remember the TP-LINK can act as a router, access point, client, bridge, or a repeater.

The Raspberry Pi and Router both fit in a Small Container for Travel

The Raspberry Pi and Router both fit in a Small Container for Travel

Network Security

Before configuring your Raspberry Pi, the first thing you should do is change all the default security related settings for the router. Start with the default SSID and the PSK password. Both these default values are printed right on the router. That’s motivation enough to change!

TP-LINK Administration Console 2

Additionally, change the default IP address of the router and the username and password for the browser-based Administration Console.

TP-LINK Administration Console

Lastly, pick the most secure protocol possible. I chose ‘WPA-PSK/WPA2-PSK’. All these changes are done through the TP-LINK’s browser-based Administration Console.

Configuring Multiple Wireless Networks

In an earlier post, Installing a Miniature WiFi Module on the Raspberry Pi (w/ Roaming Enabled), I detailed the installation and configuration of a Miniature WiFi Module, from Adafruit Industries, on a Pi running Soft-float Debian “wheezy”. I normally connect my Pi to my home wireless network. I wanted to continue to do this in the house, but connect the new router when traveling.

Based on the earlier post, I was already using Jouni Malinen’s wpa_supplicant, the WPA Supplicant for Linux, BSD, Mac OS X, and Windows with support for WPA and WPA2. This made network configuration relatively simple. If you use wpa_supplicant, your ‘/etc/network/interfaces’ file should look like the following. If you’re not familiar with configuring the interfaces file for wpa_supplicant, this post on NoWiresSecurity.com is a good starting point.

Interfaces File

Note that in this example, I am using DHCP for all wireless network connections. If you chose to use static IP addresses for any of the networks, you will have to change the interfaces file accordingly. Once you add multiple networks, configuring static IP addresses for each network, becomes more complex. That is my next project…

First, I generated a new pre-shared key (PSK) for the router’s SSID configuration using the following command. Substitute your own SSID (‘your_ssid’) and passphrase (‘your_passphrase’).

wpa_passphrase your_ssid your_passphrase

Based your SSID and passphrase, this command will generate a pre-shared key (PSK), similar to the following. Save or copy the PSK to the clipboard. We will need the PSK in the next step.

Creating PSK 2

Then, I modified my wpa_supplicant configuration file with the following command:

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

I added the second network configuration, similar to the existing configuration for my home wireless network, using the newly generated PSK. Below is an example of what mine looks like (of course, not the actual PSKs).

WPA Supplicant Configuration

Depending on your Raspberry Pi and router configurations, your wpa_supplicant configuration will look slightly different. You may wish to add more settings. Don’t consider my example the absolute right way for your networks.

Wireless Network Priority

Note the priority of the TP-LINK router is set to 2, while my home NETGEAR router is set to 1. This ensures wpa_supplicant will attempt to connect to the TP-LINK network first, before attempting the home network. The higher number gets priority. The best resource I’ve found, which explains all the configuration options is detail, is here. In this example wpa_supplicant configuration file, priority is explained this way, ‘by default, all networks will get same priority group (0). If some of the networks are more desirable, this field can be used to change the order in which wpa_supplicant goes through the networks when selecting a BSS. The priority groups will be iterated in decreasing priority (i.e., the larger the priority value, the sooner the network is matched against the scan results). Within each priority group, networks will be selected based on security policy, signal strength, etc.’

Conclusion

If you want an easy, inexpensive, secure way to connect to your Raspberry Pi, in the vehicle or other location, a travel-size wireless router is a great solution. Best of all, configuring it for your Raspberry Pi is simple if you use wpa_supplicant.

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