Hardware Reference
In-Depth Information
Chapter 8
SD Card Storage
The file system is central to the Unix system design, from which Linux borrows. The
necessary mass storage requirements have traditionally been fulfilled through hard disk
subsystems. However, as Linux hosts become as small as cell phones, flash memory
technology has replaced the bulky mechanical drive.
SD Card Media
The standard SD card is 32 mm long, 24 mm wide, and 2.1 mm thick. Figure
8-1
illustrates
the connections available on the underside of the SD card. The schematic excerpt shown
later will document how the connections are made to this media.
Figure 8-1.
SD card pinout
SD Card Interface
In the Raspberry Pi, the SD card is interfaced to the SoC through GPIO pins 46 through
53, seen in Figure
8-2
. The SoC senses the insertion of an SD card through the closing of a
socket switch (pins 10 and 11 of the socket). Thus GPIO 47 is brought to ground potential
when the socket is occupied.
