Raspberry B crashes when Wifi stick plugged in

Hi there,
I am running some Raspberries, one B+ and two B.
The B+ with its 4 USBs works as it should, but both B models are behaving
something strange.
As soon as I plug in a WLAN-USB-stick, it crashes and instantly starts a
reboot. I tested this with two different sticks, one is called "VILROS"
and was included in the B+ "starter package", and the other one is
"Edimax", which show up in dmesg as follows:
[1001 dimke@linuxnb3 ~]$ dmesg | tail -f
usb 7-2: Product: 802.11n WLAN Adapter
usb 7-2: Manufacturer: Realtek
usb 7-2: SerialNumber: 00e04c000001
usb 7-2: USB disconnect, device number 9
usb 7-2: new high speed USB device number 10 using ehci_hcd
usb 7-2: New USB device found, idVendor=7392, idProduct=7811
usb 7-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 7-2: Product: 802.11n WLAN Adapter
usb 7-2: Manufacturer: Realtek
usb 7-2: SerialNumber: 00e04c000001
I tested it on both B models and with both USB ports each.
Is this a know issue, or may this be related to the fact, that my B+
model is made in England and packed by Vilros / US, and the Bs are both
made in China?
Additionally, when pluggin the Wifi stick in before booting, it will
connect to the WLAN, but the data throughput is horribly slow -- it's
around 8 MBit/sec.
Any info highly appreciated!
Best regards,
Markus
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Reply to
Markus R. Kessler
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This happens with every wifi stick on every B, it's a power issue. The B+ has improved power handling.
Reply to
A. Dumas
On Sun, 13 Dec 2015 18:30:11 -0000 (UTC), "Markus R. Kessler" declaimed the following:
Likely need more information... Are there any other USB devices connected?
If I understand the design, the Ethernet connection is really a translator to USB, AND both it and the pure USB ports all connect to single root/host port...
Running a slow/medium speed device on the USB (mouse/keyboard) could heavily impact the overall throughput as the root is constantly switching between polling at lower speeds for mouse/keyboard data and then maybe going to highest speed to poll the network connections.
Medium speed ("full") peaks at just 12Mbps -- and even high speed (nominally 480Mbps) tends to be limited to just 280Mbps effective rate. Could the WiFi adapters really be just USB-2 "full speed"? (If they were designed with the concept of being used in public WiFi areas, a WiFi-g node is probably distributing its peak 54Mbps among multiple users... 10 users would leave just 5Mbps per user -- so a WiFi adapter may not have been built with a really high-speed USB transfer, on the basis that "full speed" can eat 25% of a shared WiFi-g node).
And I see my propensity for haranguing crowds with hypotheticals is still active... Hope some of the above gives indications for future exploration. (Note: my googling also pointed out that the R-Pi USB tends to undergo brown-out reboots when hot-plugging high drain USB devices).
--
	Wulfraed                 Dennis Lee Bieber         AF6VN 
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/
Reply to
Dennis Lee Bieber
The 5v "Wall Wort" supplied with the 2 B has more current capability From the Vilros 2 B adapter 5vdc @ 2A
Reply to
Charlie
USB2 hubs support SPLIT transactions so that a mixed speed set of devices on a hub is not a problem.
Reply to
mm0fmf
It does not. I'm using this stick on an original 256MB Model B with no problems. It is the only USB device attached though.
formatting link

---druck
Reply to
druck
What makes the rpi reboot is the power surge when plugging in/out. But assuming you (also) meant that by "using" then I guess I was wrong and nano-sticks are OK. Power draw under some threshold, apparently. Sorry.
Reply to
A. Dumas
Am Sun, 13 Dec 2015 14:24:32 -0500 schrieb Dennis Lee Bieber:
Hi,
sorry for late response.
The crashes occur with and without a second USB device plugged in.
When testing data transmission rate on Wifi there's a "PS/2-to-USB-Y- cable" plugged in, too, which brings together a PS/2 keyboard and a USB mouse (with USB-to-PS/2-adaptor).
Yes, seems to be one single bus for all.
could
is
Yes, if using a USB hub between R-PI B and Wifi stick, it won't crash.
Best regards,
Markus
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Reply to
Markus R. Kessler
As others have said; it's simply a power issue. This is a well known issue and there's nothing you can realisitcally do without picking up a soldering iron or not hot-plugging Wi-Fi dongles.
The B+ and v2 have USB power control chips which help protect against USB power surges when you plug a new device into a USB port - the earlier Pi's don't. It's further compunded by the input polyfuse on the micro USB power connector. Some people have had success by soldering small (e.g. 47µF) capacitors directly to the power pins on the USB sockets on the Pi to help soak up the surge of plugging something into the USB.
I'm guessing the hub here is powered or has some internal power decoupling capacitors which are helping to ease the initial surge.
Gordon
Reply to
Gordon Henderson

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