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as the title suggested, I am trying to add 2 ethernet interface and several USB port to my Rasp Pi. Since this will be used in project and the client wanted me to make the device as small as possible, using already available USB hub and USB to ethernet is not possible. In fact, I did so for first prototype, and it is rejected.

So, because RPi used Lan9512 as the ethernet controller and USB hub, I think I could cascade the chip to give me the additional two ethernet port and USB port for USB to serial chip, USB to parallel chip, and a 3G modem. The configuration is as follow:

  1. RPi ==> LAN9512 #1 ==> LAN9512 #2, 3G Modem + Ethernet Port #1
  2. LAN9512 #2 ==> USB-Serial Chip, USB-Parallel chip + Ethernet Port #2

Please see image below for more clear description:

Image and Connection Explanation

Unfortunately, my design is not working. I have not attached the USB-Serial, USB-Parallel, and 3G Modem yet, still not working. Running ifconfig only shows the original eth0 port, and lsusb also only shows the default USB hub. My additional Lan9512 is not detected at all.

My question is, is my design concept flawed (e.g. I cannot just cascade a USB hub on top on other hub, and then cascade it again)? Or do I need to recompile the OS, make some driver adjustment perhaps? Because I thought because Lan 9512 is basically a USB device, I can just plug it into RPi USB port, and use it as hub for other Lan9512.

I checked the RPi USB port, connect it directly to the USB Serial and USB Parallel circuit that I made, and it works (running lsusb shows FTDI devices that I used). I checked the voltage across the LAN9512 chip, and it shows 3.3v which is the correct operating voltage of LAN9512.

I am pretty confused, so if anybody can give me heads up, that will be great. Thanks guys!

migrated from electronics.stackexchange.com Jun 11 '14 at 17:16

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  • What happens if you plug it into a pc, does it work then? – cde Jun 11 '14 at 16:30
  • Do you have a specific question? Since you are working with hardware I will ask to obligatory question: "Is your power supply big enough?" – Craig Jun 11 '14 at 18:55
  • @cde, nope, the same. Voltage for the chip is 3.3v and available. USB voltage is 5v, not dropping. – bonchenko Jun 12 '14 at 5:36
  • @Craig I think so. I used 5V 3A supply, and checking voltages on the chip on a testpoint, it shows 3.3v, not dropping. Voltage on USB VCC pin is 5V I think it should be straightly recognized, yes? No need to install specific driver since LAN9512 USB is included in the kernel as it is used by default on the board (I used B version) – bonchenko Jun 12 '14 at 5:39
  • Did you try to plug in your extra-board into the PC's USB connector? Does your PC able to detect this board? – user34424 Sep 5 '15 at 18:58

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