beaglebone-black - Flipbook - Page 95
BeagleBone Black
voltage into any other pin of the expansion connectors. Based on the board design, this rail is limited to 1A
per pin to the BeagleBone Black.
There are several precautions that need to be taken when working with the expansion headers to prevent
damage to the board.
1. Do not apply any voltages to any I/O pins when the board is not powered on. 2. Do not drive any external
signals into the I/O pins until after the VDD_3V3B rail is up. 3. Do not apply any voltages that are generated
from external sources. 4. If voltages are generated from the VDD_5V signal, those supplies must not become
active until after the VDD_3V3B rail is up. 5. If you are applying signals from other boards into the expansion
headers, make sure you power the board up after you power up the BeagleBone Black or make the connections
after power is applied on both boards.
Powering the processor via its I/O pins can cause damage to the processor.
8.5 Mechanical
This section provides the guidelines for the creation of expansion boards from a mechanical standpoint. De昀椀ned
is a standard board size that is the same pro昀椀le as the BeagleBone Black. It is expected that the majority of
expansion boards created will be of standard size. It is possible to create boards of other sizes and in some
cases this is required, as in the case of an LCD larger than the BeagleBone Black board.
8.5.1 Standard Cape Size
Fig. 8.10: Cape Board Dimensions
A slot is provided for the Ethernet connector to stick up higher than the cape when mounted. This also acts as
a key function to ensure that the cape is oriented correctly. Space is also provided to allow access to the user
LEDs and reset button on the main board.
Some people have inquired as to the di昀昀erence in the radius of the corners of the BeagleBone Black and why
they are di昀昀erent. This is a result of having the BeagleBone 昀椀t into the Altoids style tin.
It is not required that the cape be exactly like the BeagleBone Black board in this respect.
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Chapter 8. Cape Board Support
