beaglebone-black - Flipbook - Page 33
BeagleBone Black
5.4.4 Power Sources
The board can be powered from four di昀昀erent sources:
• A USB port on a PC
• A 5VDC 1A power supply plugged into the DC connector.
• A power supply with a USB connector.
• Expansion connectors
The USB cable is shipped with each board. This port is limited to 500mA by the Power Management IC. It is
possible to change the settings in the TPS65217C to increase this current, but only after the initial boot. And,
at that point the PC most likely will complain, but you can also use a dual connector USB cable to the PC to get
to 1A.
The power supply is not provided with the board but can be easily obtained from numerous sources. A 1A
supply is su昀케cient to power the board, but if there is a cape plugged into the board or you have a power
hungry device or hub plugged into the host port, then more current may needed from the DC supply.
Power routed to the board via the expansion header could be provided from power derived on a cape. The DC
supply should be well regulated and 5V +/-.25V.
5.4.5 Reset Button
When pressed and released, causes a reset of the board. The reset button used on the BeagleBone Black is a
little larger than the one used on the original BeagleBone. It has also been moved out to the edge of the board
so that it is more accessible.
5.4.6 Power Button
A power button is provided near the reset button close to the Ethernet connector. This button takes advantage
of the input to the PMIC for power down features. While a lot of capes have a button, it was decided to add this
feature to the board to ensure everyone had access to some new features. These features include:
• Interrupt is sent to the processor to facilitate an orderly shutdown to save 昀椀les and to un-mount drives.
• Provides ability to let processor put board into a sleep mode to save power.
• Can alert processor to wake up from sleep mode and restore state before sleep was entered.
If you hold the button down longer than 8 seconds, the board will power o昀昀 if you release the button when the
power LED turns o昀昀. If you continue to hold it, the board will power back up completing a power cycle.
We recommend that you use this method to power down the board. It will also help prevent contamination of
the SD card or the eMMC.
If you do not remove the power jack, you can press the button again and the board will power up.
5.4.7 Indicators
There are a total of 昀椀ve blue LEDs on the board.
• One blue power LED indicates that power is applied and the power management IC is up. If this LED
昀氀ashes when applying power, it means that an excess current 昀氀ow was detected and the PMIC has shut
down.
• Four blue LEDs that can be controlled via the SW by setting GPIO pins.
In addition, there are two LEDs on the RJ45 to provide Ethernet status indication. One is yellow (100M Link up
if on) and the other is green (Indicating tra昀케c when 昀氀ashing).
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Chapter 5. BeagleBone Black High Level Speci昀椀cation
