USB device connect resets 512M Raspberry Pi (most USB devices).

Jan Holst Jensen wrote:

 

I suspect that the USB power surge when an offending device is connected and powers up, is causing the Pi to reset. This did not happen on a previous revision of the Pi - I have three older 256M Pi's and they can all have all of the above USB devices hot-plugged without resetting (as you would expect).

 

...

 

I have two different types of 1000 mA 5V power supplies that I have tested with. There is no difference in behavior. I have even tried to buffer the on-board 5V by connecting a flat-ribbon cable to the P1 connector and then, via the ribbon cable wires, connect a 4700 uF capacitor across 5V and GND (pin 2 -> pin 6). No effect.

Here is my guess:

The rev 1 RasPi had polyfuses F1 and F2 which filtered the +5.0V Vbus going to the USB devices.   F1 and F2 were changed to 0 Ohm jumpers for the last batches of rev 1 RasPis.  The rev 2 RasPi doesn't have F1 and F2 at all.  According to the schematic, the USB Vbus signals are directly connected to 5V0 so any noise is directly coupled and you can't play with F1 and F2 like you could with a rev 1 board.  So it may be a design flaw rather than a manufacturing error and if so, replacement boards won't work any better.

The 4700 uF cap should have helped, especially with the audio.  However, a large cap may have too much inductance to filter sharp spikes.

If you have a spare USB cable, you might hack the Vbus line and insert a 1-2 Ohm resistor to simulate the filtering effect of the polyfuse.  That would test my hypothesis.  An LC circuit would filter without a voltage drop.  An externally-powered hub should also work if it has good power filtering (many don't).

Also, do check TP1-TP2 with a voltmeter.  It should be at least 4.8V, but many people are able to run RasPi with as little as 4.2V.  However, it's conceivable that you're right at the threshold of reliable operation and the current surge of plugging in a new device is enough to trigger misbehavior.  It's unlikely that this is the problem, but it's an easy test.

John Beetem wrote:

 

Jan Holst Jensen wrote:

 

I suspect that the USB power surge when an offending device is connected and powers up, is causing the Pi to reset. This did not happen on a previous revision of the Pi - I have three older 256M Pi's and they can all have all of the above USB devices hot-plugged without resetting (as you would expect).

 

...

 

I have two different types of 1000 mA 5V power supplies that I have tested with. There is no difference in behavior. I have even tried to buffer the on-board 5V by connecting a flat-ribbon cable to the P1 connector and then, via the ribbon cable wires, connect a 4700 uF capacitor across 5V and GND (pin 2 -> pin 6). No effect.

 

Here is my guess:

 

The rev 1 RasPi had polyfuses F1 and F2 which filtered the +5.0V Vbus going to the USB devices.   F1 and F2 were changed to 0 Ohm jumpers for the last batches of rev 1 RasPis.  The rev 2 RasPi doesn't have F1 and F2 at all.  According to the schematic, the USB Vbus signals are directly connected to 5V0 so any noise is directly coupled and you can't play with F1 and F2 like you could with a rev 1 board.  So it may be a design flaw rather than a manufacturing error and if so, replacement boards won't work any better.

 

The 4700 uF cap should have helped, especially with the audio.  However, a large cap may have too much inductance to filter sharp spikes.

 

If you have a spare USB cable, you might hack the Vbus line and insert a 1-2 Ohm resistor to simulate the filtering effect of the polyfuse.  That would test my hypothesis.  An LC circuit would filter without a voltage drop.  An externally-powered hub should also work if it has good power filtering (many don't).

 

Also, do check TP1-TP2 with a voltmeter.  It should be at least 4.8V, but many people are able to run RasPi with as little as 4.2V.  However, it's conceivable that you're right at the threshold of reliable operation and the current surge of plugging in a new device is enough to trigger misbehavior.  It's unlikely that this is the problem, but it's an easy test.

I had begun to suspect the ommision of the USB fuses too, since they were a major design change in the later revisions. Your explanation makes perfect sense - unfortunately :-(.

I can understand the reasons for removing the USB fuses - larger current draw possible for power-hungry USB devices, and the option of back-powering the Pi from a USB hub. But gaining that at the cost of making the Pi prone to a hard reset when you insert a USB memory stick, is definitely not worth it in my opinion.

I think I may have a USB cable that I can hack to insert a small resistor and test the hypothesis. Will be back later today with the results...

Jan Holst Jensen wrote:

 

John Beetem wrote:

 

Jan Holst Jensen wrote:

 

I suspect that the USB power surge when an offending device is connected and powers up, is causing the Pi to reset. This did not happen on a previous revision of the Pi - I have three older 256M Pi's and they can all have all of the above USB devices hot-plugged without resetting (as you would expect).

 

...

 

I have two different types of 1000 mA 5V power supplies that I have tested with. There is no difference in behavior. I have even tried to buffer the on-board 5V by connecting a flat-ribbon cable to the P1 connector and then, via the ribbon cable wires, connect a 4700 uF capacitor across 5V and GND (pin 2 -> pin 6). No effect.

 

Here is my guess:

 

The rev 1 RasPi had polyfuses F1 and F2 which filtered the +5.0V Vbus going to the USB devices.   F1 and F2 were changed to 0 Ohm jumpers for the last batches of rev 1 RasPis.  The rev 2 RasPi doesn't have F1 and F2 at all.  According to the schematic, the USB Vbus signals are directly connected to 5V0 so any noise is directly coupled and you can't play with F1 and F2 like you could with a rev 1 board.  So it may be a design flaw rather than a manufacturing error and if so, replacement boards won't work any better.

 

...

 

If you have a spare USB cable, you might hack the Vbus line and insert a 1-2 Ohm resistor to simulate the filtering effect of the polyfuse.  That would test my hypothesis.  An LC circuit would filter without a voltage drop.  An externally-powered hub should also work if it has good power filtering (many don't).

I put together a USB extension cable and just having that extra wire between the USB ports and the devices does make a difference. My Wi-Fi dongle and the two previously-failing memory sticks can now be plugged into a running Pi - and it stays up. But, it is not enough to keep it going when I plug in my USB-powered speakers.

I did not have a small-enough resistor at hand but I had an inductor so I inserted that small inductor in the +5V wire. It was not enough. I then added a 470 uF capacitor across +5V and GND, after the inductor, so the extension cable has an LC bridge. Not enough either, but then - I don't know how big that inductor is...

Then I tried just having the capacitor across +5V and GND in the extension cable - a real dumb "dummy USB device": Charge a capacitor when plugged in, then do nothing. A 470 uF capacitor is enough to trigger a reset of the Pi - sometimes. And a 1000 uF capacitor does the job every time. The old 256M board stays alive in both cases.

With regards to main board voltage: I checked TP1-TP2 and it hovers around 4.72 which is at the low end. One of my power supplies has adjustable voltage and I ramped it up to "6V" leaving me with 5.6V on the main board - should be plenty. It still resets when I plug in the Kingston memory stick.

I will ask on the Raspberry Pi forum whether there are any plans for changing the design so we can get the fuses back in or some other form of current limitation. As it is, the USB ports are not at all user-friendly and the resets have now cost me data loss on two SD cards that I have had to re-image.

Jan Holst Jensen wrote:

 

...

 

I will ask on the Raspberry Pi forum whether there are any plans for changing the design so we can get the fuses back in or some other form of current limitation. As it is, the USB ports are not at all user-friendly and the resets have now cost me data loss on two SD cards that I have had to re-image.

No need to ask. They have already had a long discussion over it, and it sounds like a lot of people have had problems with the USB ports providing too little current:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=5830&hilit=usb+reset

So they decided to remove the USB port fuses. Which apparently makes a lot of people happy - just not me. I guess this is the way the Pi works until a major board revision is done :-(.

Can anyone suggest good (more stable) alternatives to the Pi in the 100-150 EUR range ? I just want a small thing that runs Linux from an SD card and uses a USB power supply (since I now have a few of those :-) )...

Jan Holst Jensen wrote:

 

Can anyone suggest good (more stable) alternatives to the Pi in the 100-150 EUR range ? I just want a small thing that runs Linux from an SD card and uses a USB power supply (since I now have a few of those :-) )...

Here are some good element14 threads.  We love talking about the latest offerings

Interesting "Competitors" for the Raspberry Pi

New kid on the block - meet OLinuXino

Wanted, help finding embedded linux board

Jan Holst Jensen wrote:

 

Can anyone suggest good (more stable) alternatives to the Pi in the 100-150 EUR range ? I just want a small thing that runs Linux from an SD card and uses a USB power supply (since I now have a few of those :-) )...

Here are some good element14 threads.  We love talking about the latest offerings

Interesting "Competitors" for the Raspberry Pi

New kid on the block - meet OLinuXino

Wanted, help finding embedded linux board