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Multiple Ethernet ports on the raspberry pi

Former Member

Hi all,

i'm interested in getting an additional Ethernet port hooked up to the raspberry pi.

the project is to create a home server (nas) and router from a raspberry pi, and I don't want wifi.

 

the final box should have both USB ports free for attaching multiple drives, or a drive and a printer(these are externally powered, not to be taken into account powerwise, the Ethernet port is the main issue).

the pi should be powered by an external power supply (although managing to power it from a pc's USB port will be awesome (using the console cable)

 

future upgrades might include replacing the second Ethernet port with an adsl modem or with a 3G modem.

 

i'm have experience with Linux. the electronics is the part I don't remember much.

 

I've searched and can't find an Ethernet add on board. I can't even find a USB Ethernet adapter.

I reckon it's because lack of interest though, and not cause it's not possible.

 

to make a long story short, is it at all possible?

 

thanks

  • There are modules like this.

     

     

    https://www.sparkfun.com/products/9473

     

    That is by no means the only one, they are SPI based, so you might be able to do what you want.

     

    Mike

  • in reply to mconners

    I wouldn't recommend that adapter. IIRC that's one that will enable your microcontroller to talk 'ethernet' easily.

     

    Search for usb ethernet on ebay and you'll find sub-$5 modules that perform the task.

     

    When you specify that you need to keep at least two ports free for other stuff, I recommend that you get an USB HUB with a hefty powersupply (2.1A min, 2.5A recommended). Then use one port of the pi to connect to the extra Ethernet port, use the other to connect to the hub. With a bit of luck the pi will power up by being powered from the upstream port from the hub and you'll be left with 4 free ports. Otherwise you need to use one downstream port for powering the 'pi leaving you with only 3 free ports in the hub.

     

    The difficulty lies with the hub. If you by a cheap hub it will have the upstream and all downstream 5V lines connected together, able to be powered from the external powersupply. However, expensive ones may leave the upstream 5V disconnected and the downstream ports currentlimited at about 500mA (too little to power a 'pi). :-(

    (As I always buy the cheap stuff, I haven't seen that last possibilty myself. ;-)

  • in reply to mconners

    How do I go about connecting it to the pi?

    Is there any documentation for the pi that I should look at?

  • in reply to rew

    Sorry, last comment regarding the Wiznet 5100.

    As for the hub suggestion I save it for last resort, unless someone can recommend a specific model.

     

    Thanks to both of you for answering

  • in reply to Former Member

    As Mike mentions, it would likely connect to the SPI pins of the RPI header (SPI is a standard, so there is lots of information on it). However, these types of devices have their own stack, so the documentation that you'd also need to consult depends on the particular device you use. It would be a lot of software development effort to do what you're planning to do (NAS and router), and probably you'll be trailblazing so uncharted territory. But feasible.

    As Roger suggests, the alternative is to just plug in a USB network adapter. This is almost guaranteed to work if you have drivers and can sort out power considerations, hub, etc (some of this might not be trivial either).

    After all that though, I'm not sure it would be worth it. A dedicated NAS may cost about the same, and will perform way better, but I understand people may wish to do it for educational purposes.

  • in reply to Former Member

    Well, you connect it to the SPI pins on the GPIO pins near the TV connector. Then you write a kernel-driver to talk to the chip and you're done!

  • in reply to rew

    Well, you got me there... Writing a kernel driver is way beyond me current abilities...

     

    Guess I'll be sticking with plan B: the USB adapter.

     

    As for getting a commercial Nas,  the actual point is the router/firewall.

  • in reply to Former Member

    The onboard Ethernet is on the USB bus. It's built into a USB hub chip that connects to the single USB host port on the BCM chip.

     

    You can get USB hubs with built-in Ethernet port. They probably use similar hub chips to the one on the Pi.

     

    There is no super fast data bus on the Pi to connect lots of high bandwith network ports to.

     

    The simplest option is probably to connect up a cheap Ethernet switch.

     

    If you main interest is in configuring your own router / firewall you might be better to get a standard router and put dd-wrt or similar on it. People use these things as internet radios and the like. Plenty of Ethernet ports and a USB host, probably a serial port in there somewhere too.

  • in reply to rew

    I agree the powered usb hub with an ethernet adapter would probably be the best solution. Writing an SPI based ethernet device driver would be a challenge. Probably doable, but a challenge nonetheless.

     

    Mike

  • I don't know what the status of RasPi USB is nowadays, but early on there were fairly severe limits on how many USB devices you could attach and still get reliable operation.  I believe it was a limitation of the BCM2835 SoC, which has a rather limited USB controller.  The BCM2835 is a media processor designed a few USB devices and may not be able to support lots of Ethernet dongles and disk drives.  I don't know what RasPi operating systems are able to support today, but I suspect you'd be better off with a SoC that has native Ethernet (instead of through USB) and SATA.