PoE (Power over Ethernet)

IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power.

IEEE 802.3at-2009 PoE standard provides up to 25.5 W of DC power (also known as PoE+ or PoE plus)

What is the difference between passive and active PoE?
If your device uses 802.3af or 802.3at it is considered to use active POE. What that means is that the device will check the power coming in and if it doesn’t meet the device requirements it won’t power up. 802.3at actually does a hand shake between the sending and receiving POE devices and won’t power up if the receiving device doesn’t acknowledge.
Passive POE usually refers to any device using POE to power that is not 802.3af/at. This includes things like cameras and radio antennas that run on 24V POE. Passive POE does not do a hand shake so it is extremely important to know what POE voltage your device requires before plugging in the CAT5 cable and powering it up. If you connect the wrong voltage you can easily burn up your device.

Raspberry Pi Auto Start Boot Time

sudo nano /etc/rc.local

Add commands below the comment, but leave the line exit 0

If your command runs continuously (perhaps runs an infinite loop) or is likely not to exit, you must be sure to fork the process by adding an ampersand to the end of the command, like so:

python /home/pi/myscript.py &

or

sh /home/pi/myscript.sh &

NOTE: Doesn’t work on cold restart (power down and up)!

Alternative Method:

sudo nano /etc/init.d/myscript
sudo chmod 755 /etc/init.d/myscript

Note: init.d Scripting is complex!

sudo update-rc.d myscript defaults