Looking for a work around, RbPi isn't getting enough power

[inDux]

Hey All,

I was fortunate enough to get a RbPi for free from a friend; however I'm told it's an older model that has some power problems. I've already encountered one: I cannot get enough power to have a Wifi dongle and keyboard plugged in at the same time. I've tried using a USB hub that has its own power to help alleviate the problem but it still doesn't let me use both at the same time.

I've created a script that will automatically join my RbPi to the network on boot but I still need to log into the Pi for this to happen (right?). Have you gotten your Pi onto your Wifi network without having to touch the keyboard? Here's my script, but it wasn't working for me before:

Code: Select all

#! /bin/bash
ifconfig wlan0
iwconfig wlan0 essid "NETWORK_ID" key s:"WIRELESS_KEY"
dhclient wlan0

I put the quotes in verbatim, if there's anything wrong with this script please let me know.

Thanks,
inDux

[abishur]

The overall issue here is that you probably have a version of the model B that has the 140 mA limiting fuse on each usb port. Meaning that each port can fully power any device on the USB ports provided they don't take more than 140 mA. The most likely scenario is that your wifi dongle draws more than 140mA which is why it doesn't work. The best work around for this is to hook it up to a powered hub, or use one of those y cables, plug one end into the pi, and one end into a spare USB wall wart (you know plugs into an AC outlet, gives you one USB port). Otherwise if you're feeling really adventurous you can talk a soldering iron to the fuses and remove them (but be careful, I used too much force and accidentally ripped the contact pad off one of them and now I can't use the associated USB port )

However, having typed all that I see in your post that you've tried using a powered USB hub to no avail. What's the current rating on your keyboard and wifi dongle?

Also to answer your main questions, you could take the appropriate steps and place your scripts in init.d to have your script run prior to boot (okay it's more complicated than that, but googling init.d script will point you in the right direction.) or you could edit ~/.profiles and have it call your script at the end, but that one would only run when that specific user logged on. And it would run *every* time the user logged on, even if you logged in remotely

[Fludizz]

If your wifi and keyboard are still interfering with eachother when using a powered USB hub, you might have a different problem

If you want to work around the problem where there is not enough power comming to the USB ports, you can 'bridge' the Polyfuses F1 and/or F2. These fuses are located between the USB ports and the LED's on early models. I did this on my Rev1 model like this:


Regarding getting wifi to work from boot, in raspbian you could add this information into /etc/network/interfaces or use NetworkManager if it is installed.

[inDux]

Thanks for the tips abishur! You are clearly very knowledgable with Rasberrys!

I forgot to mention that I placed the script in the init.d directory. But basically it sounds like init.d runs without having the need to log in, but I'll do some more research. I think what I'm going to do for the time being is to just set it up to with with my wifi network using that script and enable an ssh connection. That way I only need the wifi dongle powered to actually play with the device (I can skip on the HDMI out, maybe that will save power too!)

I just realized I'm really screwed if the dongle uses more than 140 mA in which case I need to either rip off the fuses as you suggested or make a bridge as Fludizz suggested. Thanks btw Fludizz, the picture really helps me out too!

[abishur]

Having ripped them off, if I could go back and do it again, I would do the bridging method. But all that is only relevant provided you're using one of the pis shown in fludizz's photo. The fuses are green with "T014" on them, the resistors are black with "0", and the capacitor is a tan color. If you have the resistor or capacitor then you wouldn't be limited to 140mA. It's also possible that if you do have the fuses then your powered USB hub is "back feeding" power to the pi. This is when, for whatever reason, the designer allows power to go back down the uplink port. In this situation, with the fuses only, the fuses can trip because too much current trying to be sent back over them. (which *might* explain why your pi isn't working even with the powered hub) The solution is still to bridge out the fuses.