Logitech MK120 Keys Respawning Too Fast

There might be some useful comments and pointers in this discussion: http://www.element14.com/community/message/80227, which references the RasPi Troubleshooting Wiki.

A lot of strange RasPi problems are due to iffy power.  For example, some keyboards may need closer to 5.0V to work than others, or if the 5V goes too low the SoC works but the USB chip doesn't.

There might be some useful comments and pointers in this discussion: http://www.element14.com/community/message/80227, which references the RasPi Troubleshooting Wiki.

A lot of strange RasPi problems are due to iffy power.  For example, some keyboards may need closer to 5.0V to work than others, or if the 5V goes too low the SoC works but the USB chip doesn't.

A lot of strange RasPi problems are due to iffy power.  For example, some keyboards may need closer to 5.0V to work than others, or if the 5V goes too low the SoC works but the USB chip doesn't.

Ah.

I think I got my Pi model B as a kit from Adafruit, not so sure as it was a gift. The pi itself was in an element14 box.

Anyhow, it came with a USB wall plug, and on the bottom it says that the output is "5.25VDC 1A". That could be why?

If so, should I buy a different charger?

lawm wrote:

 

A lot of strange RasPi problems are due to iffy power.  For example, some keyboards may need closer to 5.0V to work than others, or if the 5V goes too low the SoC works but the USB chip doesn't.

Ah.

I think I got my Pi model B as a kit from Adafruit, not so sure as it was a gift. The pi itself was in an element14 box.

Anyhow, it came with a USB wall plug, and on the bottom it says that the output is "5.25VDC 1A". That could be why?

 

If so, should I buy a different charger?

You can have power problems even if the "wall wart" is fine.  RasPi power has to go through a Micro USB cable and then through polyfuse F3 before it can be measured at TP1 and TP2.  Some micro USB cables have very thin conductors and you get a sizeable voltage drop.  (Adafruit probably has a good cable.)  Some F3 polyfuses are out of spec and cause an excessive voltage drop.  If you have a multimeter or voltmeter, it's easy to check that the voltage between TP1 and TP2 is 4.8V to 5.2V.

Iffy power can cause many different symptoms so it's good to rule it out.  The RasPi Troubleshooting Wiki has a good section on power supply problems and shows how to check 5V at TP1 and TP2: http://elinux.org/R-Pi_Troubleshooting#Troubleshooting_power_problems.

Iffy power can cause many different symptoms so it's good to rule it out.  The RasPi Troubleshooting Wiki has a good section on power supply problems and shows how to check 5V at TP1 and TP2: http://elinux.org/R-Pi_Troubleshooting#Troubleshooting_power_problems.

Aw, man. I'll pull out the altimeter tonight

I've tried 2 power supplies now.

Even with the keyboard unplugged it still says:

Authentication Failure

 

Authentication Failure

 

Authentication Failure

 

Authentication Failure

 

Authentication Failure

 

Authentication Failure

 

Authentication Failure

 

INIT: Id "1" respawning too fast: disabled for 5 minutes

This is f*cking ridiculous.

lawm wrote:

 

I've tried 2 power supplies now.

 

Even with the keyboard unplugged it still says:

 

Authentication Failure

 

...

 

INIT: Id "1" respawning too fast: disabled for 5 minutes

Were you able to measure 5V at TP1-TP2?

John Beetem wrote:

Were you able to measure 5V at TP1-TP2?

I measured it, and I got ~4.7 volts (analog altimeter)

lawm wrote:

John Beetem wrote:

 

Were you able to measure 5V at TP1-TP2?

I measured it, and I got ~4.7 volts (analog altimeter)

4.7V is low.  It should be at least 4.75V, preferably 4.8V.  What threshold below 4.75V actually works varies depending on your peripherals.  My own RasPi works fine down to 4.65V with Logitech K120 wired keyboard, but below that my monitor starts to flake out.

Were any of the other keyboard you tried wired?  It may be that wired keyboards work with a lower voltage than wireless keyboards.  It may be that wireless keyboards typically need a full 4.75V to work.  It might be instructive to measure TP1-TP2 for your other keyboards.

Have you tried connecting your keyboard through a USB hub?  RasPi ports are only rated for low power USB, up to 100 mA each.  On RasPi version 1.0, there are 140 mA polyfuses F1 and F2 for the USB ports, and these give an additional voltage drop so USB voltage will be even lower than TP1-TP2 = 4.7V.  You can measure this at F1 and F2: one side should equal TP1 and the other slightly lower.  If you have a rev 2.0 RasPi (the one with "mounting" holes), the USB ports are directly connected to TP1 so there's no additional drop and nothing to measure.

Some wireless keyboards need a hub because they draw more than 100 mA.  It may be that the wireless keyboards have current requirements that vary with time, e.g., 50 mA quiescent and 150 mA transmitting.  This could be a problem with RasPi rev 2.0 by causing sudden changes of 5V.  Rev 2.0 does not like hot-swapping, and this is similar.  A USB hub should fix it.

Hope this helps.  You might also check the voltage across polyfuse F3 as described at the RasPi Troubleshooting wiki.  Some RasPi boards have an F3 that's out of spec.

The respawning too fast error happens even w/o a keyboard plugged in.

John Beetem wrote:

 

lawm wrote:

John Beetem wrote:

 

Were you able to measure 5V at TP1-TP2?

I measured it, and I got ~4.7 volts (analog altimeter)

4.7V is low.  It should be at least 4.75V, preferably 4.8V.  What threshold below 4.75V actually works varies depending on your peripherals.  My own RasPi works fine down to 4.65V with Logitech K120 wired keyboard, but below that my monitor starts to flake out.

 

Were any of the other keyboard you tried wired?  It may be that wired keyboards work with a lower voltage than wireless keyboards.  It may be that wireless keyboards typically need a full 4.75V to work.  It might be instructive to measure TP1-TP2 for your other keyboards.

 

Have you tried connecting your keyboard through a USB hub?  RasPi ports are only rated for low power USB, up to 100 mA each.  On RasPi version 1.0, there are 140 mA polyfuses F1 and F2 for the USB ports, and these give an additional voltage drop so USB voltage will be even lower than TP1-TP2 = 4.7V.  You can measure this at F1 and F2: one side should equal TP1 and the other slightly lower.  If you have a rev 2.0 RasPi (the one with "mounting" holes), the USB ports are directly connected to TP1 so there's no additional drop and nothing to measure.

 

Some wireless keyboards need a hub because they draw more than 100 mA.  It may be that the wireless keyboards have current requirements that vary with time, e.g., 50 mA quiescent and 150 mA transmitting.  This could be a problem with RasPi rev 2.0 by causing sudden changes of 5V.  Rev 2.0 does not like hot-swapping, and this is similar.  A USB hub should fix it.

 

Hope this helps.  You might also check the voltage across polyfuse F3 as described at the RasPi Troubleshooting wiki.  Some RasPi boards have an F3 that's out of spec.

lawm wrote:

 

The respawning too fast error happens even w/o a keyboard plugged in.

I went to raspberrypi.org and entered "respawning too fast" in the Google search box on the front page.  There were quite a few hits, so you might be able to find out something there.

I sounds like the most likely culprit is a bad SD card or a bad OS image on the SD card.

Edit: it could also be a power issue.  There are lots of good suggestions in the RasPi Troubleshooting Wiki.  With an Adafruit 5.25V supply and 4.7V at TP1-TP2, that means there's a lot of voltage drop on the Micro USB cable or across F3.  The Troubleshooting Wiki will help narrow it down.  The Wiki says that more than 0.3V across F3 is out of spec and you'd probably need to replace F3 or the board.

John Beetem wrote:

 

lawm wrote:

 

The respawning too fast error happens even w/o a keyboard plugged in.

I went to raspberrypi.org and entered "respawning too fast" in the Google search box on the front page.  There were quite a few hits, so you might be able to find out something there.

 

I sounds like the most likely culprit is a bad SD card or a bad OS image on the SD card.

ACK!

This is driving me nuts! Ok, I'll do that later.......................