Start • Progress
in Digital Audio • Digital
Audio Processing • Digital
Media Basics • Audio
Player Project • System
Timing Analysis • Hardware • SD
Card Interface • Audio
DAC Interface • 24-Minute
I2S Interface • Software • Half
Empty • Cards
on the Table • Face
the Music • Sources
and PDF
SD
CARD INTERFACE
The
SD card operates in a standard SPI mode. The
SPI0 has been used with its maximum clock of
7.5 MHz. It operates in 8-bit mode using SCK,
MOSI, and MISO lines and another port line used
as chip select (CS).
If
you have any ARM7 evaluation boards from Keil,
Olimex, IAR, Embedded Artists, or other manufacturers
and they already have an SD card interface,
you know that they all follow the same rule
of using the SSP for that purpose. The idea
is probably to give you a faster read/write
time, but the better option for this project
is to use SSP for the DAC interface. The SSP
has an eight-frame buffer (FIFO) and corresponding
interrupt source, both of which are not available
on SPI0. This means the interrupt occurs more
often when using SPI0 instead of SSP. On my
prototype built around the LPC2148, I had to
rewire it too, which wasn’t difficult.
