We have a product that has a PC running on a small board. Our product generally runs for weeks, if not months. One thing that is not very well implemented is the shutdown process. The device does not have a screen so the user cannot see the shutdown progress.

Is there a feature on Embedded PC's (smaller form factor MB's like MiniATX, MicroATX etc) that provides a hardware indication that the OS has completed the shutdown process or more specifically that power is needed/not-needed?

  • 3
    \$\begingroup\$ Does the PC board have a standard power supply? There's a PS_ON pin on ATX boards that will go high when the computer does a soft shutdown. \$\endgroup\$
    – b degnan
    Jun 9, 2016 at 15:47
  • \$\begingroup\$ No, because the critical aspects of shutdown mostly concern software state such as flushing data, syncing, and unmounting file systems. So that unspecified software will have to tell you when it is done. If there is any software controlled desequencing of hardware elements that should be included in the report as well. But your question is unanswerable because it asks for a specific without giving specifics. \$\endgroup\$ Jun 9, 2016 at 22:00
  • \$\begingroup\$ What is an "embedded pc" more specifically? \$\endgroup\$
    – Lundin
    Jun 10, 2016 at 8:59
  • \$\begingroup\$ @ChrisStratton not sure what you are talking about as those should be implimentation details of the system that can be reduced (from a system standpoint) to "I don't need power any more". It turns out that b_degnan provided me with the clue track down the answer. I know enough now to add to my question. \$\endgroup\$
    – Hucker
    Jun 11, 2016 at 11:38

2 Answers 2


I often see Power On LED, also in small form factor boards like mini-ITX, directly on the board. Also RaspberryPi has a status led, AFAIK.


The ATX standard has two pins that many be used to implement power up/down sequences: PS_ON# and PWR_OK.

PS_ON# or power on is a signal from the motherboard to the power supply. When the line is connected to ground (by the motherboard), the power supply turns on. It is internally pulled up to +5 V inside the power supply.

PWR_OK (a "power good" signal) is an output from the power supply that indicates that its output has stabilized and is ready for use. It remains low for a brief time (100–500 ms) after the PS_ON# signal is pulled low.



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