User Manual

element14 is a trademark of Premier Farnell plc 59

6.5 Micro Secure Digital

The microSD connector on the board will support a microSD card that can be used for

booting or file storage on the element14 BeagleBone Black.

6.5.1 microSD Design

Figure 36

below is the design of the microSD interface on the board.

Figure 36 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 specification. It uses

MMCO_DAT3

for that function. However, most microSD connectors still supply a CD function on the

connectors. In the element14 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

filtering.