Not a duplicate of this RPi.SE question, as I'll explain in a moment. GPIO.RPI_REVISION returns 3.

As far as I can tell, looking at my B+, there are no LEDs labeled: OK, FDX, LNK or 10M. There are two embedded in the Ethernet port, and two on the opposite side of the board. The ones on the Ethernet are unlabeled, but I can guess what they mean. The other two are labeled ACT and PWR.

PWR only turns on once in a great while. My RPi is running just fine, and the PWR diode is unlit (which others say should never happen). This is the one that confises me the most.

AMP seems to turn on under I/O heavy load. (Seems to be the equivalent of the old OK LED).

What do these lights signify?

  • My B+ only seems to have two LEDs, ACT (activity) and PWR (power). ACT flashes with SD card activity (although other software modules can also drive the LED) and PWR is on while 5V power is available. If your PWR isn't on perhaps you have a poor power supply. Mine has no Ethernet LEDs. – joan Nov 25 '14 at 17:32
  • 1
    There are another two build into the Ethernet, if you look closely in the corners. – PythonNut Nov 25 '14 at 17:43
  • 2
    So there are. I guess the yellow/orange is 100M and green is activity. – joan Nov 25 '14 at 17:57
  • Can you find your board on any official site that looks like that? Maybe its a counterfeit? – ppumkin Nov 25 '14 at 20:00
up vote 57 down vote accepted

I believe the following is correct for the B+.

Red PWR LED

  • on if power OK
  • flashes (or goes out) if the power drops below about 4.63V

Green ACT LED

  • steady on if no SD card during boot

  • irregular flashes for SD card access

Ethernet Socket Left LED (yellow)

  • on 100-Mbps connection

  • off 10-Mbps connection

Ethernet Socket Right LED (green)

  • on if link established

  • flashes for port activity

  • off if no link is established


http://www.raspberrypi.org/forums/viewtopic.php?p=577688#p577688

http://www.raspberrypi.org/forums/viewtopic.php?p=646072#p646072

http://ww1.microchip.com/downloads/en/DeviceDoc/9514.pdf

  • 1
    Ah, thank you. I suspect my power cable has a larger than normal voltage drop. – PythonNut Nov 27 '14 at 21:23
  • I usually power my Pis via the expansion header or back-powered through the USB ports (back-powering via the USB ports is not an option for the B+). – joan Nov 27 '14 at 21:28
  • What does ACT stand for? – Ciro Santilli 新疆改造中心 六四事件 法轮功 Aug 20 '16 at 16:48
  • 1
    @CiroSantilli巴拿馬文件六四事件法轮功 ACT stands for activity. It can be configured to show different types of activity but the default is to show SD card access. – joan Aug 20 '16 at 16:57

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