The SDBootstrap demo builds upon the VGA demo, and adds a simple SPI
controller, allowing files to be read from an SD Card.
The Firmware directory contains a CardContents directory, which in turn
contains a few image files, and a “manifest” file which describes what the
boot firmware should do with them.
The example manifest loads and displays each image in turn, but it’s also
possible to load and run a program.
The firmware currently contains debugging printfs – but once these are
removed (with a couple of #defines in the Makefile) the firmware should fit comfortably within 4 kilobytes.
On the Altera DE1, the resulting mini system-on-chip takes up just over
2,000 logic elements.