This chapter is from the book
This chapter is from the book
This chapter is from the book
Connecting to Ethernet
Thus far, we have talked to the BeagleBone Black through a USB connection to a computer. This is all fine and well, but the power of the BeagleBone Black is that it’s a standalone computer capable of working on its own. Our next step is to cut the cord from our computer and connect the BeagleBone Black to a network.
In accomplishing this, we can drop the USB cable from our setup and exchange it for an Ethernet cable. We also need to power our board. Ethernet, unlike USB, does not provide power in normal configurations. There’s an option called Power over Ethernet, abbreviated PoE, but this is not a normal network configuration, so we will assume you need a separate power supply. I purchased the power supply I am using from SparkFun. It has a 5V output and can provide up to 1A of current.
Most home networks use a system called Dynamic Host Configuration Protocol (DHCP). In this configuration, a component on a network is assigned an address on the network automatically. To make this easy on ourselves, we know when the BeagleBone Black is connected via USB that it has an address of 192.168.7.2. We can use this to our advantage and connect to both Ethernet and USB at the same time and see what address our board is assigned for the Ethernet connection. So, with your board already connected to the USB, plug your Ethernet cable into the board and into your network.
When you connect the Ethernet cable, you should see the lights on the Ethernet port of your board light up. This means you’ve connected! Now, to see the IP address that has been assigned, we are going to break out to a new piece of software and connect via Secure Shell (SSH). We are about to delve into the world of the Linux command line.
There are many ways to connect via SSH. If your computer runs Linux or OS X, getting to a terminal is as easy as opening a Terminal session. The commands to use are the same as you would see working on the command line of a Linux or OS X machine. Following is an example of connecting via SSH from the Linux command line first. The process is the same for OS X. We will get to Windows in a moment.
From the Terminal, execute the following command:
[brian@mercury-fedora-vm ]$ ssh root@192.168.7.2
With this command, you ask the system to use the ssh command to connect as root to the computer at 192.168.7.2, which we know is our BeagleBone Black’s USB connection. When you execute this command and you have all the connections set right, you are presented with the following prompt:
The authenticity of host '192.168.7.2 (192.168.7.2)' can't be established. ECDSA key fingerprint is c0:81:1a:f4:58:b9:51:15:00:df:ee:71:c4:d9:fd:54. Are you sure you want to continue connecting (yes/no)?
This prompt is associated with security (referring to the first S in SSH). Your computer has never connected to this host via SSH before, and it wants to validate that this is the computer you mean to connect with. What does this buy you? It allows you to be sure that the computer you are connecting to in the future is the one you intended to, with no hacker interference. You should accept this by entering yes. The ssh program will let you know that it has accepted the security key and that it is added to the list of known servers.
The authenticity of host '192.168.7.2 (192.168.7.2)' can't be established. ECDSA key fingerprint is c0:81:1a:f4:58:b9:51:15:00:df:ee:71:c4:d9:fd:54. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '192.168.7.2' (ECDSA) to the list of known hosts.
Now, you request to log in as the root user. The root account is a powerful account and should be password protected by default, but the BeagleBone Black has a blank root password by default. We will change this later before we set the board up to be on a network doing a job.
In the Windows environment, I recommend PuTTY for SSH connections. It is easy to find with a Google search, and installation is a breeze. When you start the application, you are presented with the configuration window shown in Figure 3.5. Notice in the hostname that I’ve entered the USB assigned address of your BeagleBone Black, 192.168.7.2. Just below the Host Name text entry, you select the connection type, which is SSH in this case. Once you’ve entered these settings, click the Open button.
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FIGURE 3.5 The PuTTY Configuration window.
Another window will pop up that looks a lot like the information you saw the first time you tried to connect in the Linux terminal, and it serves the same function (see Figure 3.6). Click the Yes button to accept the security key and continue by logging on.
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FIGURE 3.6 The PuTTY Security Alert window.
From here on, regardless of the operating system or Terminal application you are using, the output will be the same. That is because what you’ll see now is actually on the BeagleBone Black.
From now on, if you log in with SSH via the USB default connection, you will not see the prompt for the security key. The session will now present you with the following command prompt:
root@beaglebone:#
This is the default prompt for the default user. If you are familiar with Linux or a similar operating system, then you’ll know you’re in a Bash shell. The information provided by the prompt can be very useful and even customized. The information in Table 3.2 is presented in the default prompt.
TABLE 3.2 Default Prompt Information
Prompt Information |
Description |
root |
The information in this first block tells us the username for the shell. In our case, we logged in as root. |
beaglebone |
The hostname, on the network, we are logged in to. |
This represents the directory we’re currently working in on the file tree. In this case, the tilde is shorthand for the user’s home directory. |
Now, we are going to enter our second command. This command, called ifconfig, is used to report the current network status of the system. Let’s go ahead and enter it and then see the response:
root@beaglebone:# ifconfig
eth0 Link encap:Ethernet HWaddr 7c:66:9d:58:bd:41
inet addr:192.168.1.161 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::7e66:9dff:fe58:bd41/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4059 errors:0 dropped:2 overruns:0 frame:0
TX packets:147 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:616100 (601.6 KiB) TX bytes:18322 (17.8 KiB)
Interrupt:40
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
usb0 Link encap:Ethernet HWaddr e6:8c:89:9a:b6:c8
inet addr:192.168.7.2 Bcast:192.168.7.3 Mask:255.255.255.252
inet6 addr: fe80::e48c:89ff:fe9a:b6c8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1717 errors:0 dropped:0 overruns:0 frame:0
TX packets:136 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:200409 (195.7 KiB) TX bytes:31059 (30.3 KiB)
The results provided tell us about three different network adapters represented on the system: eth0, lo, and usb0. We can ignore lo for now; it’s the local loopback connection. The two of interest to us are eth0 and usb0. The default USB connection is usb0. There are a lot of fields here, but the field we are interested in is labeled inet addr. Here is the usb0 interface information again, with that field highlighted in bold:
usb0 Link encap:Ethernet HWaddr e6:8c:89:9a:b6:c8
inet addr:192.168.7.2 Bcast:192.168.7.3 Mask:255.255.255.252
inet6 addr: fe80::e48c:89ff:fe9a:b6c8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1717 errors:0 dropped:0 overruns:0 frame:0
TX packets:136 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:200409 (195.7 KiB) TX bytes:31059 (30.3 KiB)
The value associated with this address should look familiar. It is the same address we used to access the website and to log in to the board. Now, what we are looking for is the address that has been given to the board via DHCP. The Ethernet port is represented by interface eth0, and by looking at its inet addr field, we know that, in this case, the DHCP has assigned the board an address of 192.168.1.161, as shown here:
eth0 Link encap:Ethernet HWaddr 7c:66:9d:58:bd:41
inet addr:192.168.1.161 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::7e66:9dff:fe58:bd41/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4059 errors:0 dropped:2 overruns:0 frame:0
TX packets:147 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:616100 (601.6 KiB) TX bytes:18322 (17.8 KiB)
Interrupt:40
Unless you have changed the IP address space in your network, and if you have I trust that you know what you are doing with your network, your board will have an IP Address in one of the public IP Address spaces, either 192.168.x.x or 10.0.x.x.
Now, with the board connected to Ethernet and assigned an address on the network, you can unplug the USB connection and plug in the +5V power adapter. You’ve now put your BeagleBone Black on the network, independent of the computer you were using before. You are ready to be an active member of your home’s network ecosystem!
Let’s check the website connection via your network connection. Using your browser, navigate to the address provided earlier for eth0. In the case of my network, that’s 192.168.1.161, as you can see in Figure 3.7.
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FIGURE 3.7 Banner from the BeagleBone built-in website letting you know everything is working just fine—this time, via the Ethernet connection.
Now, let’s log in via SSH to the eth0 connection. It is going to look familiar:
[brian@mercury-fedora-vm ]$ ssh root@192.168.1.161 The authenticity of host '192.168.1.161 (192.168.1.161)' can't be established. ECDSA key fingerprint is c0:81:1a:f4:58:b9:51:15:00:df:ee:71:c4:d9:fd:54. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '192.168.1.161' (ECDSA) to the list of known hosts. Debian GNU/Linux 7 BeagleBoard.org BeagleBone Debian Image 2014-04-23 Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian Last login: Fri Jul 18 15:06:44 2014 from mercury-win.local root@beaglebone:#
As you can see, it is the same process for logging in as before, but with a different address. This example is from a Linux machine, but the process is identical as the one we used previously for PuTTY, but with a different address.
Something interesting to note is that if you run the ifconfig command, the usb0 adapter is still available. That’s because we haven’t actually changed anything in the operating system configuration; we just used a different connection. The USB option is still there waiting for us to connect, and it will be unless we turn it off in the operating system. We will get into more detail about the underlying operating system and some of the options we have for alternate operating systems on the BeagleBone Black. In our next chapter, we delve into the hardware and discuss some basics of electronics that will be necessary for many of the remaining chapters.