Just a thought, I remember having a great 10baseT low power CF ethernet card good for several hours at least for my Linux Zaurus PDA. Since we cant really expect much more than 10Mb/S from our N900s maybe there is a lower power 10baseT USB NIC?

Right, but that assumes the culprit is the device or the chipset. So, if it drains the N900 ~1500 mAh battery in an hour, it will probably drain a bigger phone battery in two hours (from full), assuming the non-USB consuption are about the same on both phones. A laptop would likewise be drained quickly. Now, assuming laptops (for sure) and tablets and phones (probably) are target market for these devices; does the maker actually expect the adapters to sell?

Looking around the web, I don't see any reviews mentioning power consumption being a problem, or evaluating it in any depth. So we still don't know what exactly is causing the drain; since that's the case, it's more difficult to begin to solve it.

But yeah, one way to see if it's really the adapter that's to blame is to try a different adapter. Note that's what I did with Plugable vs. Trendent. But ordering and returning can only be done so many times. Ok, I'll see if I can try a third device, this time an older one.

RasberryPi owners are surely conscious of power consumption, that might produce some leads.

Right, I have been searching through their discussion forums. Also there is http://elinux.org/RPi_USB_Ethernet_adapters

Note that consumption/drain data is relatively sketchy. It either works with a powered USB hub or it doesn't. E.g. they list my former Trendnet TU2-ET100 as working out of the box, but don't say for how long.

@chill

Perhaps you could obtain power from the ethernet cable via a POE device, e.g. this one on Amazon

It doesn't look like that particular cable would work, because it has a barrel connector at the other end, and the N900 doesn't have a socket for it.

But let's think about PoE as an idea. Power would come from the Ethernet (PoE) for the N900 (note that USB-Ethernet adapters cannot be powered, or none that I know can). The N900 would then simultaneously power the USB-Ethernet adapter. The problem is, how do you make it so that both the USB-Ethernet adapter and the power cable (coming from the PoE) are plugged into the N900?

One possible solution would be to use the POE device to power a hub, to which both the ethernet adaptor and the N900 would be connected.

I see. That's correct, but then you are looking at buying and maintaining three devices: PoE, USBEthernet adapter and USB hub. Given that the area where the N900 is deployed can be expected to have a wall socket (unlike where PoE is intended), this is probably not the best solution. A powered USB hub and USBEthernet adapter seems more reasonable.

So if we're looking to reduce the number of devices to just one, we want a USB-Eth adapter that is externally powered. There aren't that many of them out there. There are a few brands carrying this one but the reviews complain about the quality of the plastic. Also, there is this one. Compatibility should be ok, because it is based on the Asix AX88760 chip, which Asix's web site says uses the same driver as the AX88772 (which the N900 with power kernel recognizes, as shown by my usage of the Trendnet and Plugable adapters). However, Syba says it will 1) only operate when the external power is on and 2) it will not charge the host (N900). Ideally we'd have 1) and 2) but I guess we can live without.

An alternative would be to get a powered USB hub and use it with the existing USBEth adapter. This way we'd get 1) and 2) in exchange for operating two devices.

if you want to determine what is causing massive power drainage while using usb-rj45 adapter, you may want to perform the same tests that I suggested in other thread:
http://talk.maemo.org/showpost.php?p...6&postcount=35

+ do powertop tests. We should know if it's really the adapter draining too much power, or just device's CPU is active all the time + gods know whatsnot (or both).

Although, from my experience, hostmoding anything - be it just keyboard or mouse - result in device drawing much more current than it "should" (i.e. we're able to give only 200 mA to device connected to USB, so if your full ~1200 mAh battery drains in one hour when using ethernet adapter, it means that adapter itself could eat as much as 200 mAh, and device is eating rest of 1000 mAh on it's own).

Well, our hostmode implementation isn't a "reference one" - damn you Nokia for carrying about some stupid certification, and pulling out official hostmode support on the last moment. As a result, the fact that we have hostmode at all - even with it's speed limited by unknown reasons to under what's our WiFi offers, constant high-speed problems, and such - it's a miracle.

/Estel