beaglebone-black - Flipbook - Page 54
BeagleBone Black
Micro Secure Digital
The microSD connector on the board will support a microSD card that can be used for booting or 昀椀le storage
on the BeagleBone Black.
6.2.14
microSD Design
Fig. 6.18: microSD Design
The signals MMC0-3 are the data lines for the transfer of data between the processor and the microSD connector.
The MMC0_CLK signal clocks the data in and out of the microSD card.
The MMCO_CMD signal indicates that a command versus data is being sent.
There is no separate card detect pin in the microSD speci昀椀cation. It uses MMCO_DAT3 for that function. However, most microSD connectors still supply a CD function on the connectors. In the BeagleBone Black design,
this pin is connected to the MMC0_SDCD pin for use by the processor. You can also change the pin to GPIO0_6,
which is able to wake up the processor from a sleep mode when an microSD card is inserted into the connector.
Pullup resistors are provided on the signals to increase the rise times of the signals to overcome PCB capacitance.
Power is provided from the VDD_3V3B rail and a 10uF capacitor is provided for 昀椀ltering.
6.3 6.6 User LEDs
There are four user LEDs on the BeagleBone Black. These are connected to GPIO pins on the processor. Figure
37 shows the interfaces for the user LEDs.
Resistors R71-R74 were changed to 4.75K on the revision A5B and later boards.
Table 6.5: User LED Control Signals/Pins
LED
GPIO SIGNAL
PROC PIN
USR0
USR1
USR2
USR3
GPIO1_21
GPIO1_22
GPIO1_23
GPIO1_24
V15
U15
T15
V16
A logic level of “1” will cause the LEDs to turn on.
6.3. 6.6 User LEDs
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