RPi different boards?
#1
I have two RPi both 512MB. They have been tested with the same power supply, Flirc and IR and the same openelec build (no hub used).
One is working normal the other one is having problems. For example Flirc on the other one is sometimes working sometimes is not recognized, the logitech keyboard works ok on both.
I assume that it has to have something with HW revisions to do.
Are there any tweaks to set something. I assume that it has to do something with USB.

On sticker it is printed:
E3912RS2V13B1.0
Made in U.K.

Also if i ssh into it it does not list always Clay Logis USB device which is Flirc.
Also i have noticed that one is hotplug capable, the other one is not.
Reply
#2
Thee should be no functional difference in the two pi's.
Can you swap the pi's over, leaving power supply, sdcard and peripherals unswapped.
Does the problem move with the Pi, or stay?
Reply
#3
I have already did this. It simply acts different.
Reply
#4
What is the age of each board ? Is one a lot older than the other ?

There were some revisions made to the boards over time, in particular the 100mA polyfuses powering the USB ports were deleted fairly early on.

Also the main polyfuse F3 can go faulty with age (or rarely, faulty from new) causing it to be higher than normal resistance. This could explain why you can hot swap USB devices on one board and not the other.

You really need to check the voltage across TP1 and TP2 on both boards under the same test conditions, I think you'll find that a difference in voltage drop across the main polyfuse is the difference between the boards. It certainly fits the symptoms:

http://elinux.org/R-Pi_Troubleshooting#T...r_problems
Kodi 18.3 - Mid 2007 Mac Mini, 4GB, 2TB HD, Windows 7 SP1
Kodi 18.3 - Vero4k, Raspberry Pi 2. OSMC.
Reply
#5
I can really testify to the USB cable problem!
When I started up my Pi for RASPBMC in January it did install but could not access the Internet afterwards.
I had the most frustrating experience trying to solve this until I checked the Pi voltage across TP1-TP2 and found it to be 4.6V!!!!
And this with a 2A USB power supply.
The culprit was the USB cable and I fixed it by cutting away the cable between the connectors and splicing in a reasonable size twin copper wire.
Since then I get 5.2V on my Pi (TP1-TP2) and all works excellently!

If you use a power supply with a fixed USB cable instead of an USB connector on the body you would probably not get this issue, but as is most common there is this darned USB cable in between that causes the problem.

The strange thing for me was that the Pi itself seemed to run (got RASPBMC show XBMC on screen etc), but it could not access the Internet and download add-ons.
I have never used a WiFi for any of my Pi units, just straight Ethernet wired LAN.
Bo Berglund
Sweden
Reply
#6
(2014-06-29, 14:02)Bosse_B Wrote: The strange thing for me was that the Pi itself seemed to run (got RASPBMC show XBMC on screen etc), but it could not access the Internet and download add-ons.
I have never used a WiFi for my PiConfused, just straight Ethernet wired LAN.

That's quite common. The arm and gpu run off 3.3V. (Although the input voltage needs to be higher than this).
USB and Ethernet run off 5V.

Typically with low voltage it's USB and/or Ethernet that goes out of spec first.
Some USB devices are more tolerant of below spec voltage, but below 4.75V you shouldn't be surprised by errors and disconnects.
Reply
#7
Right, but as a new user of a Pi with the intention to just set up XBMC and get it configured I suspect that the capacity for analysis of the problem down to finding out that the cause is the darned cable is probably beyond the ordinary user.
I am a retired electronics and software engineer (MScEE) so I have at least the equipment needed to trace this down, but it was not the first thing I thought about, I must say.

I have now read the thread DBMandrake pointed to including its follow-up links and I do hope Farnell heeds the advice and makes sure that the power supply "designed for" the Pi really also has a proper power cable in the package....
Bo Berglund
Sweden
Reply
#8
(2014-06-29, 17:35)Bosse_B Wrote: Right, but as a new user of a Pi with the intention to just set up XBMC and get it configured I suspect that the capacity for analysis of the problem down to finding out that the cause is the darned cable is probably beyond the ordinary user.
I am a retired electronics and software engineer (MScEE) so I have at least the equipment needed to trace this down, but it was not the first thing I thought about, I must say.
I have an electronics background too (although not currently practicing in my day job...) so I have a good understanding of the voltage drop issues the Pi suffers from, but it's very hard to convince people sometimes that their random crash/freeze/loss of Ethernet etc really, honestly, probably is a voltage drop issue, and that until they rule that out by actually measuring it, they're running around in circles looking for a software "fix" that doesn't exist.

It doesn't matter that the label on their power adaptor says 5v 1amp, rarely for a USB charger does that mean it is still actually putting out 5v at 1amp, (they're poorly regulated, if at all) and then you have issues with the cable like you had, or a faulty polyfuse, or a combination of the three.

A high percentage of the problems reported here and over in the raspbmc forum (I'd say 60%) which often seem bizarre and inscrutable are almost certainly just power issues.

Those people that take the advice to check the voltage more often than not find their power adaptors aren't up to snuff, fix the voltage drop problem and the problems they were having disappear. But there are a significant percentage that won't accept the advice to check the voltage - "I have a 5v 2amp supply, it should be fine", "it was working fine with Frodo so it can't be the power supply" etc...despite the fact that us regulars see the same problems reported over and over and they are nearly always proven to be power related...

With bad power Pi's are woefully unstable, with good power they are remarkably stable. I've had almost zero trouble with mine, it runs 24/7 for weeks on end with a 1000Mhz overclock without a reboot, its had all kinds of abuse while doing test/development work and it is as stable as can be, so they can be very good.

Quote:I have now read the thread DBMandrake pointed to including its follow-up links and I do hope Farnell heeds the advice and makes sure that the power supply "designed for" the Pi really also has a proper power cable in the package....
I link to that page for any possible voltage related issues because it neatly explains the issue and how test for it - anyone with access to a multimeter can follow the instructions even without an electronics background. Not everyone has a multimeter of course but a cheap one can be had for almost nothing, considering how cheap the Pi is compared to other HTPC systems its not a huge burden to get one to help troubleshoot problems.

IMHO the Raspberry Pi foundation made a serious design error by leaving out the 5 volt regulator (and DC barrel jack) that the Alpha boards had in an effort to cut costs and keep it below their arbitrary $35 target price, now we have millions of Raspberry Pi's out there that are hypercritical about their power adaptors and the Pi has a bit of a reputation for being unstable because of it.

That's what we have to work with though - use a good power supply and cable and it does work very well.
Kodi 18.3 - Mid 2007 Mac Mini, 4GB, 2TB HD, Windows 7 SP1
Kodi 18.3 - Vero4k, Raspberry Pi 2. OSMC.
Reply
#9
Hmm. I will measure it but not at home atm so will do it in 14 days. Strange i have seen both problems with network loosing connection and usb not working. Both require stable 5v as you have said. Since on both rpi the same cable and power supply was used i assume that the couse are polyfuses. Can someone tell me which one are and if they can be replaced and where to get them. And also how to be sure that polyfuses are the problem.
Also if i would be powering pi over pins on i/o header will the same voltage drop be present or. In ther word are the same fuses used when powering over pins.

P.s.
I have found all answers. Polyfuses should recover but there is posibillity that they were already defekt.
Powering over pins actually bypasses fuses but needs very stable power since already 6v would harm pi.
Reply
#10
(2014-06-29, 18:02)DBMandrake Wrote: I link to that page for any possible voltage related issues because it neatly explains the issue and how test for it - anyone with access to a multimeter can follow the instructions even without an electronics background. Not everyone has a multimeter of course but a cheap one can be had for almost nothing, considering how cheap the Pi is compared to other HTPC systems its not a huge burden to get one to help troubleshoot problems.

IMHO the Raspberry Pi foundation made a serious design error by leaving out the 5 volt regulator (and DC barrel jack) that the Alpha boards had in an effort to cut costs and keep it below their arbitrary $35 target price, now we have millions of Raspberry Pi's out there that are hypercritical about their power adaptors and the Pi has a bit of a reputation for being unstable because of it.

That's what we have to work with though - use a good power supply and cable and it does work very well.

Be aware that the testing procedure for the f3 fuse on that page is wrong. The procedure has you checking open circuit voltage, for a valid test of volt drop you need the PI running with an sd card inserted and whatever peripherals you use plugged in so the circuit is loaded. I'm 99% sure of this, anyone else have any opinions?
If I have been of help, please add to my reputation as a way of saying thanks, it's free.
Reply
#11
(2014-06-29, 21:02)Dilligaf Wrote: Be aware that the testing procedure for the f3 fuse on that page is wrong. The procedure has you checking open circuit voltage, for a valid test of volt drop you need the PI running with an sd card inserted and whatever peripherals you use plugged in so the circuit is loaded. I'm 99% sure of this, anyone else have any opinions?
Well it's not open circuit voltage - even without an SD card plugged in the Pi will still draw current even though it appears dead apart from the red LED - how much current I don't know, it's probably somewhat less than the maximum current draw when booted and over clocked though.

So the test is valid, but perhaps not as accurate as it would be if the Pi was fully booted up at your normal over clock and with peripherals installed. But in that case everyone's results are going to be different because people use different over clocks and have different peripherals, whereas a non-booting no-peripherals test would give a meaningful comparison between Pi's owned by different people by eliminating those variables.

Personally I would check it both ways - you don't really want more than 0.3v (I'd say 2.5v actually) loss across the polyfuse in any operating condition.
Kodi 18.3 - Mid 2007 Mac Mini, 4GB, 2TB HD, Windows 7 SP1
Kodi 18.3 - Vero4k, Raspberry Pi 2. OSMC.
Reply

Logout Mark Read Team Forum Stats Members Help
RPi different boards?0