Fix for problems with ethernet and wlan in fast-booting pipaOS

[Obsolescence]

Hi,

For most people, the pipaOS image worked fine.
But a few people mentioned they had problems with getting wifi to work on the pipaOS disk image.

Today, I had too.

Problem:
I plugged in a Wifi dongle, and it got assigned wlan1 instead of wlan0. And wlan1 is not configured.

Solution:
There must be a more intelligent way, but this worked for me:

1. sudo nano /etc/udev/rules.d/70-persistent-net.rules
2. You will see multiple entries for wlan devices (at the end of each line).
3. remove all lines referring to wlan devices except the last one
   (normally, you delete wlan0, but maybe wlan1 if you plugged in other wifi dongles and there's a wlan2)
4. rename the last wlanX device in the list to wlan0, save and reboot.

Explanation:
This file keeps track of any devices you plugged in to give them a persistent name. As I plugged in *my* dongle before making the disk image, it's in there. Yours is added afterwards. And gets to be named wlan1.

Remains the question why most people have no problems (including myself up to today). I do not really know.

Ethernet fix
Similar solution if you cannot get the Ethernet connection to work: delete all the ethX lines except the last one and rename it to eth0.


There should be a more elegant fix, but for now this works. Recommendations invited!

Regards,

Oscar.



[Roger Smith]

I don't think this is particularly a pipaOS problem, it's more to do with the persistent-net-rules business (which I alternately bless and curse). As a last resort you should be able to delete all wlan<x> entries from that file, and then plug in the wifi dongle you intend to use to get an entry for wlan0.
Roger

[Dylan McNamee]

I'm experiencing this problem, but another puzzling one as well, with PipaOS. The second problem I'm seeing is that the power consumption of the WiFi dongle seems to be pushing my Pi (A+) into a power-supply issue: when I plug in my WiFi thingy, dmesg is cluttered with USB errors, and the LED's are dimmer.  Is anyone else seeing this or something similar? My USB hub isn't (yet) powered, but I think I'll have to go to a powered hub to get this working.

dylan

--

[Norman Davie]

I'm also seeing the "infamous" rainbow block showing up on the hdmi display -- something that I never saw with the old build.
Also I can send keystrokes to the pi from my terminal, but not back to the terminal using a USB Serial dongle -- again probably a power issue.
Booting the old image I don't have any problem with communications between the devices or the low power indicator.

[Dylan McNamee]

I can confirm that replacing my unpowered USB hub with a powered one (don't yet know how I'll do that with the case closed and one power in) seems to have fixed everything with my setup, which included some weird SDcard read errors and other flakiness. Seems that power to the RPi through the PiDP/8 PCB is not sufficient in all cases to drive USB peripherals...

[Obsolescence]

Dylan,

So pipaOS seems to draw more power than the standard Raspbian? At least with your wifi dongle? How bizarre... I wonder whether it's specific to this dongle?

Regards,

Oscar.

[Dylan McNamee]

Did I read in the release notes that the latest version of the software has a modification that makes the LED's brighter? That could be the cause of the power difference.

dylan
--

[Norman Davie]

I think you're right Dylan.  I just updated my software to the latest version on the original SDCard, it is shows occasional power dips as well -- I guess I need a slightly beefier power supply (more than 2.1 amp)

[AB]

Hi norman - do you have a power supply recommendation?  I was unaware that >2.1A was something I should be messing with- is that even "allowed?"
cheers
Andy

[Obsolescence]

Hi,

Powering the Pi turns out to be a non-trivial topic.

I mostly used the Model A+. Which, as it turned out, has the nice characteristic of using **much** less power than the B+ or 2. The A+ can be easily run off the power of a laptop's USB connector. That seems to be true for the Zero as well.

Doing that with a B+ is OK, but is pushing things.

Not so for the Pi 2. It really needs a good power supply. Otherwise, you'll end up with a corrupted SD card at some point.

To be honest, not that I am an expert in the field, but the way the Pi deals with power is, well, bad. The fact that you need a 2-3A power supply for something that really draws no more than 0.5A shows the Pi was made on a budget. Its power circuitry just assumes perfect power more than it should.

Maybe one reason (...) not to replace an end-of-life PDP-8 with a PiDP-8 if you operate a nuclear plant.

Regards,

Oscar.

[Peter Willard]

I agree. The Pi, with it's high power requirements, never should have been built with the idea that you would grab your spare phone or tablet charger to operate it.  I mean... if they had added a built in virtual serial USB adapter into the USB port that would be one thing, but to build it to use a USB adapter that exceeds the power specifications of USB means that they really should have tried to use a common 5V HUB power supply. Like http://bit.ly/1rehdaB. 

I mean, it's clear *why* they did it.  That doesn't make it right. 

 

[Oscar Vermeulen]

Peter,

Indeed. The gripe I have with the Pi 2 especially (but also the 3, B+ and, I guess B) is that the thing really only uses <400mA.

The otherwise ridiculous need for a beefy 2-2.5A power supply is just because the Pi can't handle even the smallest voltage fluctuation from the PS when it briefly needs a few more mA to drive the SD card. I am an idiot when it comes to analog electronics, but it seems to me that a capacitor with $0.02 of tidbits would solve the problem for everyone.

The problem seems to be that the 5->3.3V regulator sits behind a polyfuse that causes a voltage drop. So if a within-spec 4.9500V power supply sits behind a cable with maybe an additional 0.25V voltage drop, the voltage reaching the regulator falls out of spec quickly. It's not mA but voltage stability which is the Achilles heel.

Oh well. Nothing is perfect. But it leads me to a preference for an A+ or Zero. Or recommending the original Pi power supply with the 2/3.

The A+ has another problem, its USB is just not really compliant with USB specs. It is very picky when it comes to USB hubs. This one is the best I've tried so far. The Zero is said to be more relaxed when it comes to USB hubs.

Regards,

Oscar.

[Peter Willard]

 Right.  I have a collection of tested hubs marked so that I KNOW they will work with a pi.  The rest I own are verified to be not working.  I can't just grab any hub.    

[Tom Stewart]

Well, I hope if you are operating a Nuke plant, you can spring for a 3A power supply... ;-)