USB Ethernet power consumption

[projectdp]

I'm setting up my Pi as a router and I wanted to use two ethernet interfaces.

Does anyone have experience with this? How can I determine the power consumption with various devices?

I know I can figure it out 'on paper' by the spec sheet of the ethernet dongle and the normal draw of the R-Pi, but I want to do it manually. I have a few tools but I'm not quite sure how I'd determine the nominal power draw.

Would a powered USB port be generally able to handle two interfaces in this configuration?

Thanks everyone, first post btw.

[mahjongg]

Just be aware that the PI's USB ports only use <100mA devices (so called single current unit devices, which work with 4,4 Volt) because a fuse in the PI limits the current hard to 140mA, and also cause some voltage drop.

[S3B]

Hey Projectdp

What conclusions did you draw from trying this?
I am interested to know as I am looking at creating a Pi network analysis system.
Apparently you have tried this before too?
I am looking at having it on mirrored ports, but also need to look into the possibility of having it bridging the connection of two switches / switch and pc.

Any advice would be much appreciated

S3B

[heychris]

Hi,

I'm a network engineer and have quite a few usb ethernet adapters for various projects. I also have a meter I picked up on ebay. It's a USB in/out with a amp/volt meter. I can actually measure the amperage before and after plugging in a usb ethernet adapter. For example. A common ebay cheap usb-ethernet adapter usually runs DM9601 chipset. I think mine was $3 or so. RPi has the driver built in.
before usb adapter - .365A
after plugging in usb- .407A
with ethernet attached and link light on - .410A

I hope that helps

[heychris]

I am also looking for a RPi based network analysis unit. It'd be great to have something to simulate traffic, measure packet loss, etc.

Also a simple server with TFTP, FTP, DHCP, etc would be quite handy.

[heychris]

I also tried an older usb ethernet adapter. This one is a linksys USB200M v2

without usb ethernet .365A
with usb ethernet no cat5 .589A
with usb ethernet and cat5 .541A

max of 224mA
The reason I mention this is that it's significantly more than the 42mA with the new chipset.

The one I just picked up on ebay uses the Davicom dm9601 chipset and the linksys runs a Asix AX88772. I'd guess the linksys one is almost 10 years old.